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  • Analytical Chemistry and Spectroscopy  (25,705)
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  • 1
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    ISSN: 0935-6304
    Keywords: High-performance liquid chromatography ; β-methyl amino acids ; enantioseparation ; quinine-derived chiral stationary phase ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A quinine-derived chiral anion-exchange stationary phase was used for the direct high-performance liquid chromatographic separation of the enantiomers of the N-protected unusual β-substituted α-amino acids, β-methylphenylalanine, β-methyltyrosine, β-methyltryptophan, and β-methyl-1,2,3,4-tetrahydroisoquinoline-3-carboxylic acid. The readily prepared 2,4-dinitrophenyl and tert-butyloxycarbonyl derivatives were well separated, and in most cases the separation of all four stereoisomers of these β-methyl-α-amino acids could be obtained in one chromatographic run. The elution sequences of the enantiomers of the different derivatives were determined and revealed a dependence on the type of the N-protecting group. In this context, the effects of different protecting groups (acetyl, tert-butyloxycarbonyl, benzoyl, 3,5-dinitrobenzoyl, benzyloxycarbonyl, 3,5-dinitrobenzyloxycarbonyl, 2,4-dinitrophenyl, and 9-fluorenylmethoxycarbonyl) on the chromatographic behavior were investigated.
    Additional Material: 6 Ill.
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  • 2
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    ISSN: 0935-6304
    Keywords: Monolith ; continuous bed column ; convective interaction media ; membrane chromatography ; membrane adsorber ; HPMDC ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Monolithic stationary phases have revolutionized protein chromatography because they combine speed, capacity, and resolution in a unique manner. Since such stationary phases contain no particles but only flow-through pores, the usual mass transfer restrictions to the chromatography of large molecules are not observed and extremely fast separations become possible. Recently the area of application of monolith chromatography has been extended to the separation and analysis of small molecules and plasmid DNA. This review summarizes the state of art in high performance monolith and especially high performance monolithic disk chromatography (HPMDC). The current understanding of the theory of protein HPMDC is summarized, while an introduction to the evolving field of small molecule HPMDC is attempted. The basic differences between the monolithic disks and columns packed with conventional stationary phases (including perfusion and micropellicular particles) but also monolithic columns (porous rods) are outlined. Finally, the potential of HPMDC to analytical and preparative biochromatography is demonstrated by a discussion of recent applications of chromatographic disks for protein isolation and bioprocess analysis.
    Additional Material: 14 Ill.
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  • 3
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    ISSN: 0935-6304
    Keywords: In situ molecular imprinting ; continuous polymer rod ; miniaturized column ; chiral recognition ; diastereoselectivity ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Molecularly imprinted continuous polymer rods are prepared inside PEEK tubes of 1 mm i. d. by an in situ preparation technique; and chiral separations on such media have been demonstrated. The miniaturized column filled with (-)-cinchonidine-imprinted or (+)-cinchonine-imprinted polymer rods based on a copolymer of 2-(trifluoromethyl)acrylic acid and ethylene glycol dimethacrylate permitted diastereoseparation of (-)-cinchonidine and (+)-cinchonine; the template molecule is retained to a greater extent than the corresponding antipode. Increasing the amount of cyclohexanol in the polymerization mixture decreased the backpressure of the resultant rod and the addition of latex beads suspended in water to the prepolymerization mixture affected the selectivity and affinity of the imprinted polymer rods. The column length is adjusted easily by cutting, thus allowing easy control of retention behavior and analysis time.
    Additional Material: 1 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    ISSN: 0935-6304
    Keywords: Preparative chromatography ; silica monoliths ; PrepROD™ ; productivity ; SMB-chromatography ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---The use of monolithic silica sorbents for the isolation of substances by preparative liquid chromatography is demonstrated. Preparative liquid chromatography is recognized as a valuable technique for the isolation and purification of substances in the pharmaceutical and fine chemicals industry. The system technology has meanwhile reached a high standard, and the greatest future improvements are expected to arise from new and improved adsorbents. Monolithic silica sorbents offer some unique features for preparative liquid chromatography. They exhibit high efficiencies even at high flow rates due to their fast convective mass transfer and can therefore be used at very high mobile phase velocities, leading to high productivity and hence to maximum process economy. The benefits of this new type of adsorbent are illustrated for an example in batch-chromatographic mode and an example using the continuous simulated moving bed (SMB) technology.
    Additional Material: 6 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    ISSN: 0935-6304
    Keywords: Analysis of anthraquinones ; capillary electrophoresis ; high-performance liquid chromatography ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---The separation and determination of twelve anthraquinones, viz. anthraquinone 1, chrysphanol 2, aloe-emodin 3, alizarin 4, anthraquinone-2-carboxylic acid 5, purpurin 6, sennoside B 7, sennoside A 8, emodin 9, quinalizarin 10, rhein 11, and anthraflavic acid 12, were achieved by capillary electrophoresis (CE) and high-performance liquid chromatography (HPLC). Detection at 260 nm with a buffer solution containing 30 mM sodium borate (adjusted to pH = 10.56 with 0.05N NaOH) and acetonitrile (9 : 1) in CE or with a linear gradient elution containing 20 mM KH2PO4 with 0.05% phosphoric acid (pH = 2.91) and methanol in HPLC was found to be the most suitable approach for this separation. Contents of six components (2, 3, 7, 8, 9, 11) in crude Rhei Rhizoma extract could easily be determined within 39 min by CE or 63 min by HPLC. The effects of buffers on this separation and the validation of the two methods were studied.
    Additional Material: 5 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    ISSN: 0935-6304
    Keywords: Capillary gas chromatography ; trichlorophenols ; ammonia ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---No abstract
    Additional Material: 1 Tab.
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  • 7
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    ISSN: 0935-6304
    Keywords: Comprehensive two-dimensional GC ; peak overlap ; statistical-overlap theory ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---The need for two-dimensional gas chromatography is justified by the extent of peak overlap in one-dimensional gas chromatograms (GCs) of complex mixtures. Such overlap was predicted long ago by statistical-overlap theory (SOT). In this paper, SOT is conceptually reviewed and its predictions are shown to be quantitatively accurate. GCs of complex mixtures of polychlorinated biphenyls, pyridine- and nitrogen-containing polynuclear aromatic hydrocarbons, tetrachlorodibenzo-p-dioxins and dibenzofurans, fatty acid methyl esters, flavors and fragrances, and naphtha were simulated by commercial GC software on DB-1, DB-5, and Stabilwax stationary phases. The numbers of peak maxima in the GCs agreed with predictions of SOT, when the interval of time between successive peaks of pure compounds was described by Poisson statistics. This agreement was realized even though the time intervals actually are deterministic, not statistical. In addition, the numbers of mixture components were predicted with accuracy by regression of peak numbers against SOT. Similar regressions have been reported before, but the theory used here is more sophisticated and its predictions consequently are more accurate. Future directions for finalizing SOT are suggested.
    Additional Material: 4 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    ISSN: 0935-6304
    Keywords: Sample preparation ; gas extraction techniques ; membrane-type techniques ; water analysis ; soil analysis ; gas chromatography ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---This review focuses on the role of so-called solventless methods of sample preparation in contemporary environmental analysis. The basic classification of this group of methods as well as the principal features and advantages of the techniques in current use are discussed.
    Additional Material: 2 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    ISSN: 0935-6304
    Keywords: Comprehensive gas chromatography ; cryogenic modulation ; semi-volatile aromatics ; thermal sweeper ; peak widths ; peak asymmetries ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---The two current technologies for achieving comprehensive gas chromatography (GC×GC) - the thermal sweeper and the cryogenic modulator - are compared in an interlaboratory study using a multicomponent semi-volatile aromatic compound sample. The same column set (phases, film thickness, dimensions of columns) and conditions of oven temperature program were used. Carrier gas flow settings however were different for the data reported here. The thermal sweeper has a longer overall length due to the extra ca. 30 cm length of narrow bore tubing used for the modulator/accumulator section. Data reveal that the two methods behave in an analogous manner in respect of delivering GC×GC results, with key peak parameters of peak widths and symmetry measures showing good correlation. Retention time dissimilarity on the first dimension columns in the two systems arises from different flow rates used, however the second column retention is similar, and this is due to the resulting different elution temperatures that peaks elute on the first dimension in each system. Overall, the two approaches to GC×GC appear to produce equivalent results within the scope of the application studied. Each system does have its experimental limitations; the thermal sweeper has what may be called a ‘thick film effect’, where at high temperature it can be difficult to sufficiently trap the migrating bands in the accumulator column, and the pulsing of solutes in the cryogenic system may suffer from a ‘thick wall effect’ if a column with too thick a wall dimension is used at low oven temperature.
    Additional Material: 4 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    ISSN: 0935-6304
    Keywords: μLC ; FID ; LC-FID ; carbohydrates ; amino acids ; alcohols ; phosphonic acids ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---The potential of the on-line coupling of microcolumn liquid chromatography (μLC) using aqueous eluents with a flame ionization detector (FID) was evaluated. An eluent-jet interface was modified to allow the efficient introduction of the eluent into the FID. The potential of the method is demonstrated by the μLC-FID determination of lower alcohols and bis(2-hydroxyethylthio)alkanes on porous and non-porous stationary phases, respectively. Flow injection analysis (FIA)-FID experiments with highly polar, thermolabile, semi-volatile and non-volatile compounds like amino acids, organic acids, alkylphosphonic acids, and carbohydrates showed the developed configuration to be a promising approach for the detection of a wide range of analytes. Compared with a nebulization interface, the eluent-jet interface showed 4-10 times higher peaks for citric acid. Detection limits by FIA for all compounds were in the range of 0.2-5 ng injected. With ribose as test compound, plots of peak height vs. amount injected showed good linearity (r2 〉 0.999) in the range of 75-12,000 μg/mL. The repeatability showed relative standard deviations of less than 5%.
    Additional Material: 7 Ill.
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  • 11
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    ISSN: 0935-6304
    Keywords: Antioxidants ; propyl gallate ; octyl gallate ; dodecyl gallate ; butylated hydroxyanisole ; butylated hydroxytoluene ; reverse-phase liquid chromatography ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---The influence of cationic and anionic surfactants and short-chain alcohols in the mobile phase on the retention of five antioxidants has been studied. The solutes chosen were butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), and propyl, octyl, and dodecyl gallates (PG, OG, DG).The surfactants were hexadecyltrimethylammonium bromide (CTAB) and sodium dodecyl sulfate (SDS), and n-propanol (PrOH) was the selected alcohol. A simple isocratic reversed-phase method for the antioxidant determination is proposed. Separation of five primary antioxidants takes 18 min with the mobile phase SDS 0.10 M/H3PO4 0.01 M/PrOH 30%. Variation of the percentage of alcohol in the mobile phase permits optimization of the retention times of the antioxidants. Detection limits in the pg range were obtained for the all solutes. The method was used to determine the antioxidants in olive oil at three different levels, giving mean recoveries close to 100% for all the solutes (BHA 102%, PG 99%, OG 99%, DG 99%) except BHT (84%).
    Additional Material: 3 Ill.
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  • 12
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    ISSN: 0935-6304
    Keywords: HPLC ; industrial wastewater ; process development ; 4-amino-azobenzene-4′,5-disulfonic acid (AABDS) ; 4-amino-azobenzene (AAB) ; 4-amino-azobenzene-4′-sulfonic acid (AABS) ; 4-amino-azobenzene-4′,3,5-trisulfonic acid (AABTS) ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---A simple and rapid reversed-phase high-performance liquid chromatographic method for the separation and determination of 4-amino-azobenzene-4′,5-disulfonic acid (AABDS) and its process-related impurities was developed. The separation was achieved on a μ-Bondapak C18 column using 0.15 M ammonium sulfate-acetonitrile (55:45) (v/v) as eluent. A UV-visible spectrophotometric detector fixed at 386 nm was used both for detection and quantitation. The method was used not only for quality assurance but also for process development and wastewater management of AABDS.
    Additional Material: 4 Ill.
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  • 13
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    ISSN: 0935-6304
    Keywords: Conjugated linoleic acids ; underivatized ; Ag+-HPLC ; resolution ; mixed mode retention ; hydrogen bonding ; competing acid ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Fatty acids (FAs) and fatty acid residues are generally methylated and analyzed by GC. The reasons for this are partly historic and partly because of the sensitivity advantage of flame ionization detection over UV absorption by the carboxylic acid functionality in saturated FAs. However, for strongly absorbing unsaturated acids such as the conjugated linoleic acids (CLAs), the sensitivity advantage is greatly reduced. Hence there seems little reason to waste time and introduce errors associated with methylation. Remarkably, this appears not to have been recognized. In this paper we describe our method development for the analysis of underivatized CLAs by silver ion HPLC separation on the ChromSpher Lipids column. Using mobile phases previously optimized for the analysis of the methylated CLAs, retention is excessive and a competing acid is required. Various combinations of small concentrations of acetic acid (3.0-2.5%) with acetonitrile (0.0-0.025%), respectively, yield similar resolution and run times. As well as its role as a competing acid, acetic acid acts as a general strong solvent and thus can be used alone as a modifier (without acetonitrile). However, for slightly shorter run times a mobile phase of 2.5% acetic acid and 0.025% acetonitrile was chosen as the optimum mobile phase for analysis. The separation of the free CLAs is clearly superior to those previously published and obtained in this study for the methylated CLAs. The additional specific strong interactions of the underivatized CLAs seem certain to be due to hydrogen bonding between the CLA carboxylic acid functionality and the large number of residual silanols on the surface of the silica support of the stationary phase.
    Additional Material: 6 Ill.
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  • 14
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    ISSN: 0935-6304
    Keywords: Liquid chromatography ; chiral separation ; chiral stationary phase ; separation of enantiomers ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---A new reciprocal π-basic chiral stationary phase (CSP) was designed based on the reciprocity conception of chiral recognition and prepared starting from (S)-leucine. The CSP thus prepared was applied in resolving various π-acidic N-(3,5-dinitrobenzoyl)-α-amino amides and esters and found to be very effective. Especially, N-(3,5-dinitrobenzoyl)-α-amino N,N-dialkyl amides were resolved very well on the new reciprocal CSP. From the chromatographic resolution results and based on the reciprocity conception of chiral recognition with the aid of Corey/Pauling/Koltan (CPK) molecular model studies, a chiral recognition mechanism which utilizes π-π interaction and simultaneously two hydrogen bonding interactions between the CSP and the analyte has been proposed. The CSP prepared in this study was also successful in resolving 3,5-dinitrophenylcarbamate derivatives of 2-hydroxycarboxylic acid esters.
    Additional Material: 4 Ill.
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  • 15
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    ISSN: 0935-6304
    Keywords: SPME ; desorption ; fiber conditioning ; field sampling ; sample preparation ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: No abstract
    Additional Material: 3 Ill.
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  • 16
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    ISSN: 0935-6304
    Keywords: Polyunsaturated fatty acids (PUFA) ; high performance liquid chromatography-atmospheric pressure chemical ionization mass spectrometry (LC-MS with APCI) ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Analysis of polyunsaturated fatty acids using high performance liquid chromatography-atmospheric pressure chemical ionization mass spectrometry is described. The standard fatty acid methyl esters from 16 to 22 carbons were analyzed by LC-MS with APCI. The effect of orifice voltage and total carbon atoms versus number of double bonds in each homologue on the mass spectra is discussed. The correction coefficients for homologues from saturated fatty acids to hexaenoic acid are also mentioned.
    Additional Material: 4 Ill.
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  • 17
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    ISSN: 0935-6304
    Keywords: Silver ion high-performance liquid chromatography (Ag-HPLC) ; conjugated linoleic acid (CLA) ; p-methoxyphenacyl derivatives ; single-column Ag-HPLC ; fatty acid analysis ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---No abstract
    Additional Material: 5 Ill.
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  • 18
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    ISSN: 0935-6304
    Keywords: 2H/1H ratio analysis ; HRGC-P-IRMS ; stable isotopes ; benzaldehyde ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Isotope ratio monitoring gas chromatography-mass spectrometry of the 2H/1H ratio by pyrolysis isotope ratio mass spectrometry (P-IRMS) was used to analyze benzaldehyde originating from various sources. Based on the δ2HSMOW value of an authentic reference sample determined with an elemental analyzer (EA), the range of reproducibility and linearity was checked. Correct (EA related) and reproducible data were obtained for sample amounts 〉0.6 μg benzaldehyde (on column). In another series of experiments, the influence of sample preparation, i. e. simultaneous distillation-extraction (SDE) was found to be negligible. The following ranges of δ2HSMOW values were determined for benzaldehyde using five types of samples, i. e. (i) synthetic (δ2HSMOW -78 to -85‰, ex benzal chloride; +420 to +668‰, ex toluene) and ‘natural’ (including ‘ex-cassia’) references (δ2HSMOW -83 to -144‰); (ii) bitter almond oils (δ2HSMOW -113 to -148‰); (iii) fruits (δ2HSMOW -111 to -146‰); (iv) kernels (δ2HSMOW -115 to -188‰); and (v) leaves (δ2HSMOW -165 to -189‰).
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  • 19
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    ISSN: 0935-6304
    Keywords: Capillary HPLC ; gradient elution ; temperature programming ; phenolic compounds ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---This paper describes a liquid chromatographic method using a reversed phase capillary column coupled to an UV detector for the quantitation of thirteen pollutant phenols. Chromatographic separation was carried out with gradient elution at 25.0 ± 0.1°C. The two major anisocratic elution modes (gradient elution and temperature programming) were evaluated. The detection limit range was 10-81 pg (100 nL injected). The chromatographic method combined with liquid-liquid extraction was applied to analysis of these compounds in river water. Recoveries of 75-103% were achieved for most of them.
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  • 20
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    ISSN: 0935-6304
    Keywords: Artemisia palustris ; Asterothamnus centrali-asiaticus ; capillary gas liquid chromatography ; Compositae (Asteraceae) ; Heteropappus hispidus ; seed oil ; silver ion thin layer chromatography ; trans-fatty acids ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Seed oils from the Compositae plant family are known to contain a variety of unusual fatty acids. Subsequent to the recent discovery of γ-linolenic acid in Saussurea and Youngia, further Mongolian Compositae species were investigated for their seed oil fatty acid composition. A number of δ3trans-fatty acids (16 : 1δ3t, 18 : 1δ3t and 18 : 3δ3t, 9c, 12c) were found in the seed oils of Heteropappus hispidus and Asterothamnus centrali-asiaticus. The latter fatty acid, but not the trans-monoenes, was also found in one species of Artemisia. These unusual fatty acid isomers were characterized by capillary gas-liquid chromatographic (GLC) separations in combination with other chromatographic techniques (analytical thin layer chromatography, TLC and preparative argentation TLC), and infrared spectrocsopy (IR). Their identity was further confirmed by co-chromatography with other seed oils known to contain these trans-fatty acids. The fact that within the Compositae plant family there are apparently two or three distinct groups of genera containing δ3trans-fatty acids is discussed.
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  • 21
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    ISSN: 0935-6304
    Keywords: Open tubular columns ; capillary electrochromatography ; column efficiency ; injected volume ; applied voltage ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The effect of some instrumental parameters on column efficiency in open tubular capillary electrochromatography (OTCEC) has been evaluated. First, it was investigated whether band broadening due to the sample injection process is within a tolerable range when an open tubular column (OTC) of about 10 μm i. d. is used. As a result of the small injection profile factor (K2 = 1.3), injected volumes must be sufficiently small (less than 10 pL) to avoid a significant efficiency loss (〉5%) when hydrodynamic injection by siphoning is employed. Secondly, the kinetic performance of OTCs in a CEC system was estimated from the variation of the reduced plate height (h) with the reduced linear velocity (ν) which was controlled by the voltage applied. Reasonable agreement was obtained between the theoretical h versus ν curve and the experimental values for a group of polycyclic aromatic hydrocarbons used as test compounds. Values of 0.25 for minimum h at an optimum ν of 16 are estimated, which permit separations with around 400,000 plates per meter to be obtained in less than 5 min. Finally, the possibility of estimating the diffusion coefficients of the solutes in the mobile phase from the plot of the height of a theoretical plate versus electroosmotic flow velocity is shown.
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  • 22
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    ISSN: 0935-6304
    Keywords: On-line SFE-SFC ; organometallics ; purity testing ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: No abstract
    Additional Material: 4 Ill.
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  • 23
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    ISSN: 0935-6304
    Keywords: Capillary SFC ; zinc dialkyldithiophosphates ; lubricating oils ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: No abstract
    Additional Material: 5 Ill.
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  • 24
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    ISSN: 0935-6304
    Keywords: Supercritical fluid chromatography (SFC) ; micropacked capillary columns ; waxes ; restoring ; objects of art ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: No abstract
    Additional Material: 2 Ill.
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  • 25
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    ISSN: 0935-6304
    Keywords: Aroma ; “lulo del Chocó” ; Solanum topiro ; volatiles ; glycosidically bound volatiles ; glycoside TFA derivatives ; enantioselective gas chromatography ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---The volatile constituents of lulo del Chocó (Solanum topiro) fruit pulp obtained by liquid-liquid extraction were analyzed by capillary GC and capillary GC-MS. In total, 30 components were identified with methyl salicylate, hexadecanoic acid, hexanal, guaiacol, ethyl butanoate, and ethyl acetate being the major components. Chirospecific MDGC analysis revealed the predominance of (R)-ethyl-3-hydroxybutanoate (ee 40%) and the presence of racemic mixtures both of δ-octalactone and of δ-decalactone. For γ-hexalactone, γ-octalactone, and γ-decalactone enantiomeric distributions of 22.4 : 77.6, 22.9 : 77.1, and 20.0 : 80.0, (R) : (S), respectively, were determined. Glycosidically bound aroma compounds were identified by capillary GC and capillary GC-MS after isolation of the glycosidic fraction obtained by Amberlite XAD-2 adsorption and methanol elution followed by hydrolysis with a commercial pectinase enzyme. In total 13 bound aroma compounds (aglycones) were identified. These aglycones mainly consisted of compounds exhibiting aromatic structures. Additionally, with the aid of capillary GC and capillary GC-MS (EI and NCI) of trifluoroacetylated derivatives we identified eight glucosides: the novel 3,6-epoxy-7-megastigmen-5,9-diol β-D-glucopyranoside and the hexyl, benzyl, linalyl oxide (furanic), 2-phenylethyl, vomifolyl (isomer 1), (6S,9R)-vomifolyl, and scopoletin β-D-glucopyranosides.
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  • 26
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    ISSN: 0935-6304
    Keywords: Supercritical fluid extraction ; capillary GC ; hydrocarbons ; bio-oil ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: No abstract
    Additional Material: 3 Ill.
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  • 27
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    ISSN: 0935-6304
    Keywords: Clean-up ; aliphatic hydrocarbons ; organochlorine compounds ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---No abstract
    Additional Material: 2 Ill.
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  • 28
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    Electronic Resource
    Weinheim : Wiley-Blackwell
    ISSN: 0935-6304
    Keywords: Cyclodextrin ; capillary electrophoresis ; system peak ; CHES 1 ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Using a running buffer containing cyclodextrins (CDs) and 2-[N-cyclohexylamino]-ethanesulfonic acid (CHES), positive system peaks were observed in the analysis of a ganglioside mixture by CE-UV. These system peaks were related to CDs in the running buffer because these peaks were also detected when a plug of solution devoid of CDs but having the same CHES concentration and pH as the running buffer was injected. Neutral CDs were separated owing to the formation of inclusion complexes with the anionic CHES ion. One possible explanation for the positive system peaks is that the anionic CD-CHES inclusion complex is displaced by co-ions with higher UV absorptivity.
    Additional Material: 3 Ill.
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  • 29
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    ISSN: 0935-6304
    Keywords: Capillary electrophoresis ; enantiomer separation ; chiral drugs ; TM-γ-cyclodextrin ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---High-throughput screening is a promising new approach in analytical chemistry. Within the framework of an extended screening program (The German-Chinese Drug Screening Program), the enantioseparation of 86 drugs was investigated by capillary zone electrophoresis in the presence of the chiral solvating agent (CSA) octakis-(2,3,6-tri-O-methyl)-γ-cyclodextrin (TM-γ-CD). By this means, 15 drugs could be separated into enantiomeric pairs. Approximate measures for the degree of interaction (migration retardation factor, Rm) and for the degree of enantiomer recognition (migration separation factors, αm) revealed intriguing patterns that were compared with those found for native γ-cyclodextrin (γ-CD). Although there is a distinct influence of the analyte structure on the electrophoretic data, interpretation remains difficult. Most remarkably, permethylation of γ-CD leads neither to a higher affinity nor to better chiral recognition, in contrast to the findings with α-CD.
    Additional Material: 10 Ill.
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  • 30
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    ISSN: 0935-6304
    Keywords: Focused microwave assisted extraction ; close microwave-assisted extraction ; DDT ; soil samples ; experimental design ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Optimization of focused microwave (FMW)-assisted extraction of 4,4′-DDE, 4,4′-DDD, and 4,4′-DDT from soil samples was carried out using central composite designs. All the extracts were analyzed with GC/MS and some of them also with GC/AED using columns of different polarities for each of the techniques. The extraction of the analytes was carried out in two ways: with acetic acid as microwave radiation absorbent solvent and n-decane to concentrate the analytes and with reagent water and iso-octane as solvents. In the first case, the influence of the extraction temperature, the extraction time, and the addition of sodium chloride were studied and the optimum conditions for the extraction of 1 g of soil with 5 mL of acetic acid and 2 mL of n-decane were 1.30 mol L-1 sodium chloride at 98°C for 9.3 min. In the second case, the temperature was kept constant (94°C) and the influence of the concentration of sodium chloride and the extraction time were studied. The optimum conditions were 5 mL of a 2.0 mol L-1 sodium chloride together with 2 mL of iso-octane for 15 min. The recoveries obtained by water-FMW extraction were significantly lower than those obtained by the acetic acid-FMW procedure. These last recoveries were in good agreement with those obtained by closed microwave assisted-extraction with acetone-n-hexane as solvent.
    Additional Material: 3 Ill.
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  • 31
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    ISSN: 0935-6304
    Keywords: Gentiana rigescens Franch ; gentiopicroside ; swertiamarin ; MEKC ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: No abstract
    Additional Material: 2 Ill.
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  • 32
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    Electronic Resource
    Weinheim : Wiley-Blackwell
    ISSN: 0935-6304
    Keywords: Phenol derivatives ; RP-HPLC separation ; short RP column ; gradient elution ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---No abstract
    Additional Material: 1 Ill.
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  • 33
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    ISSN: 0935-6304
    Keywords: High performance size exclusion chromatography ; molecular weight ; lignin derivatives ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---No abstract
    Additional Material: 4 Ill.
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  • 34
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    Electronic Resource
    Weinheim : Wiley-Blackwell
    ISSN: 0935-6304
    Keywords: Domestic lignite heating emissions ; isokinetic sampling ; polyaromatic sulfur heterocycles (PASH) ; thiaarenes ; atomic emission detection (AED) ; pulsed flame photometric detection (PFPD) ; high resolution mass spectrometry (HRMS) ; retention indices ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Lignite briquettes with different sulfur contents were burned in a common type of domestic heating system. The levels of polycyclic aromatic sulfur heterocycles (PASH, thiaarenes) and their alkylated and phenylated derivatives in the flue gas were determined. The analytical method described comprises isokinetic sampling, GC/full scan-MS for screening analysis, HPLC/wavelength programmable fluorescence detection (selected PAHs used as internal standards for GC), GC/atomic emission detection or GC/pulsed flame photometric detection (sulfur-selective detection of thiaarenes), GC/high resolution MS (verification and quantification of thiaarenes), and the determination of the gas chromatographic retention indices. In total 57 thiaarene species (individual compounds if possible and groups of isomeric compounds such as alkylated/phenylated species) were identified, their retention indices determined, and quantified as flue gas emission concentrations. Not only thiophene-related thiaarenes but also species with two sulfur atoms in the molecule (e. g. thienothiophene derivatives) were found. The thiaarene emission pattern is discussed, as is the correlation between the thiaarene emissions and the sulfur content of the different briquette types burned.
    Additional Material: 11 Ill.
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  • 35
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    ISSN: 0935-6304
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Solid-phase extraction, on-line derivatization, and measurement by ion trap mass spectrometry (ITD-MS) were used to investigate the biological degradation of pharmaceutical residues (clofibric acid, ibuprofen, diclofenac). The results of the single steps of sample pretreatment and analytical determination are reported. MS/MS measurements were performed on an ITD-MS by selecting collision induced dissociation of the molecular ions (M+) as parent ions to defined daughter ions. A pilot sewage plant and biofilm reactors operating under oxic and anoxic conditions were run as model systems with synthetic sewage water containing 10 to 50 mg/L dissolved organic carbon (DOC) and pharmaceuticals in concentrations of 10 μg/L. Clofibric acid displayed its persistent character in all cases. The pilot sewage plant and the oxic biofilm reactor showed comparable results for diclofenac and ibuprofen, which both were partly degraded. These results can explain the occurrence of these substances in sewage effluents and in the aquatic environment. A high degree of degradation was found especially for ibuprofen in the oxic biofilm reactor, which was attributed to adaptation of the biofilm to the residue. Two metabolites of ibuprofen could be identified on the basis of their mass spectra and comparison with literature data, viz. hydroxyibuprofen and carboxyibuprofen.
    Additional Material: 8 Ill.
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  • 36
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    Electronic Resource
    Weinheim : Wiley-Blackwell
    ISSN: 0935-6304
    Keywords: Programmable temperature vaporizing injection (PTV) ; thermal desorption ; gas chromatography ; mass spectrometry ; plasticizers ; polyethylene ; food wrapping film ; explosive powders ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Programmable Temperature Vaporizing Injection (PTV) has been used extensively as a means of injecting large volumes of samples to enhance sensitivity. This paper describes the use of PTV injection in the desorption mode for the analysis of a range of solid samples, and four examples of this application are described in detail. Detection by mass spectrometry was used extensively as a means of identification of the components in the various samples which were characterized.
    Additional Material: 12 Ill.
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  • 37
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    Electronic Resource
    Weinheim : Wiley-Blackwell
    ISSN: 0935-6304
    Keywords: Pyrethroids ; solid-phase microextraction ; water analysis ; temperature ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Synthetic pyrethroids are increasingly being used for insect control on field crops because of their advantageous environmental properties such as short field life, broad spectrum of insecticide activity, and relatively low mammalian toxicity. In the present work, experimental conditions were optimized for trace analysis of pyrethroids in water by using solid-phase microextraction followed by capillary gas chromatography. Effects of temperature, SPME-fiber diameter, and matrix were studied. SPME used off-line with a gas chromatograph electron-capture detection (GC-ECD) showed a linear response over a wide concentration range. Our results showed a strong temperature effect on pyrethroid extraction yield. The detection limit after 5 min of SPME-fiber exposure to the samples changed from 1 ppb (at 30°C) to 0.1 ppt (at 90°C), which is a 10000 increase in pyrethroid detection. The standard deviations of the analyte peak area ratios were typically in the range of 1-7% at 30°C and of 3 to 15% at 90°C. Best conditions for pyrethroids analysis were achieved using high temperature solution and a 100 μm polydimethylsiloxane fiber. No matrix (river water) influence was observed on detection of the investigated pyrethroids.
    Additional Material: 6 Ill.
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  • 38
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    Electronic Resource
    Weinheim : Wiley-Blackwell
    ISSN: 0935-6304
    Keywords: Historical remarks ; modern separation methods ; gas chromatography ; selective sorbents ; selectors ; discovery process ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---The research conducted and the discoveries during the development of chromatography are briefly surveyed, with emphasis being placed on gas chromatography. Some actors are presented who played major roles en route from Tswett's original discovery to modern separation methods. The article is based mainly on personal memories and encounters. A few examples of the participation of our country in the development of chromatography are mentioned as well as international contacts. Some remarks are made on the use of selective sorbents or selectors in modern analytical separations. The paper closes with a few comments on the “philosophy” of the discovery process.
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  • 39
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    Electronic Resource
    Weinheim : Wiley-Blackwell
    ISSN: 0935-6304
    Keywords: Silicone oil ; supercritical fluid chromatography (SFC) ; micropacked columns ; MALDI-TOF ; GC/MS ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---No abstract
    Additional Material: 4 Ill.
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  • 40
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    ISSN: 0935-6304
    Keywords: Flavor ; odorant ; headspace ; GC ; interaction ; electronic nose ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---In order to understand the flavor of foods a multitude of scientific investigations have been carried out and a number of analytical tools for flavor research developed in the last few decades. Initially, scientific investigations focused mainly on the identification of all compounds that could contribute to the flavor. Olfactory GC techniques permitted the division of identified volatiles into odor-active and non-odor-active. Many techniques were developed to enhance the quality and the information content of the flavor results. Since the early 1990s, analytical investigations have dealt with interactions between food matrices and flavor compounds and the human influence on the retardation of odorants. New analytical methods concentrate on the headspace of the sample by using static or dynamic headspace analysis, or deal with measurements of volatile release in the mouth by a novel nose sampler and oral vapor GC. These useful tools clarify the effects of breathing, chewing, and saliva flow on flavor release. Though the human nose performs well at low concentrations of odorants, it is a medium-term aim to replace the use of the human nose by analytical techniques. Future investigations will probably deal with the interactions of odorants and the human receptors and it is mainly these receptors that will play a key role in aroma research. By analysis of the effects of odorants on the receptors the mechanisms of odor perception will be elucidated. This will enable the development of supporting analytical tools like electronic noses that really do function as noses, or “neural networks”.
    Additional Material: 9 Ill.
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  • 41
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    ISSN: 0935-6304
    Keywords: Comprehensive two-dimensional GC ; time-of-flight ; oil analysis ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---In this work a comprehensive two-dimensional system (GC×GC) was coupled to a time-of-flight mass spectrometer (TOF/MS) for the analysis of oil samples. Group-types like the alkanes and saturated cyclic compounds (naphthenes), which are present in oil, are shown separately by selecting their unique masses. On selecting appropriate ion fragments, this method also permits the determination of sulfur- and oxygen-containing species in oil. Former results obtained by FID detection could be confirmed. After proper selection of unique ions in GC×GC-TOF both selectivity and sensitivity increase.
    Additional Material: 6 Ill.
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  • 42
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    ISSN: 0935-6304
    Keywords: CZE ; indirect UV detection ; metal ions ; ecological samples ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---No abstract
    Additional Material: 5 Ill.
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  • 43
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    Electronic Resource
    Weinheim : Wiley-Blackwell
    ISSN: 0935-6304
    Keywords: Enantioselective gas chromatography ; cyclodextrins ; heptakis(2,6-di-O-tert-butyldimethylsilyl)-β-cyclodextrin ; heptakis(2,6-di-O-tert-butyldimethylsilyl-3-O-methyl)-β-cyclodextrin ; heptakis(3,6-di-O-tert-butyldimethylsilyl-2-O-methyl)-β-cyclodextrin ; octakis(2,6-di-O-tert-butyldimethylsilyl-3-O-methyl)-γ-cyclodextrin ; thermodynamic parameters ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Separation factors and thermodynamic data for the separation of various chiral analytes on different di-O-tert-butyldimethyl-silylated cyclodextrin derivatives are collected and described. Modifying the substitution pattern of the tert-butyldimethylsilyl group in position 2 and 3 or changing from β- to γ-cyclodextrin significantly affects the separation properties of the cyclodextrin derivatives.
    Additional Material: 9 Ill.
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  • 44
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    Electronic Resource
    Weinheim : Wiley-Blackwell
    ISSN: 0935-6304
    Keywords: Monofunctionalized cyclodextrins ; enantioselective capillary-HPLC ; immobilized chiral stationary phases ; separation of chiral drugs ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Heptakis(2,6-di-O-methyl-3-O-pentyl)-β-cyclodextrin was monofunctionalized by the regioselective introduction of exactly one ω-epoxyoctyl group at the primary site of the cyclodextrin. The site-specifically substituted cyclodextrin was immobilized to commercially available aminopropyl silica by nucleophilic opening of the epoxy function of the spacer substituent resulting in a lipophilic chiral stationary phase with broad applicability for enantiomer separations in capillary-HPLC under reversed-phase conditions.
    Additional Material: 6 Ill.
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  • 45
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    Electronic Resource
    Weinheim : Wiley-Blackwell
    ISSN: 0935-6304
    Keywords: Gas chromatography-mass spectrometry ; amino acid enantiomers ; D-amino acids ; physiological fluids ; mammals ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Quantities of D-amino acids were determined in body fluids (urine, blood plasma and blood serum, milk) of mammals (hamster, horse, bovine, sheep, pig, and dog). Amino acids were isolated using a cation exchanger and converted into their N(O)-pentafluoropropionyl (or trifluoroacetyl) amino acid 2-propyl esters. Enantiomers were separated and quantified on a Chirasil-L-Val capillary column with mass spectrometric detection using selected ion monitoring. D-Enantiomers of most protein L-amino acids were detected. Largest absolute and relative amounts in most cases were determined for D-Ser and D-Ala in urine. Stereoisomers of 2,6-diaminopimelic acid were also measured in bovine, ovine, and porcine urine. Since D-amino acids were detected in all representative classes of the major orders of Mammalia, namely Artiodactyla, Perissodactyla, Rodentia, and Carnivora, and taking reports in the literature into account, it is postulated that D-amino acids occur in all mammals.
    Additional Material: 5 Ill.
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  • 46
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    Electronic Resource
    Weinheim : Wiley-Blackwell
    ISSN: 0935-6304
    Keywords: Ion chromatography ; graphitic carbon stationary phases ; anions ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Inorganic anions could be separated on porous graphitic carbon stationary phases in ion chromatography. Ion exchange between eluent anions and sample anions on the stationary phase was confirmed by the retention behavior and the possibility of indirect photometric detection. The elution order of anions was different from that observed for commercially available anion exchangers. Chloride, nitrate, and sulfate contained in tap water could be determined in 7 min.
    Additional Material: 6 Ill.
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  • 47
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    Electronic Resource
    Weinheim : Wiley-Blackwell
    ISSN: 0935-6304
    Keywords: GC-MS/MS ; PCDDs ; PCDFs ; human tissue ; fish tissue ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---This paper outlines the possibilities of selectivity and sensitivity enhancement in measuring PCDD/F congeners using an ion trap GC-MS/MS. The pressure of the collision gas and the collision energy were optimized. The modified GC-MS/MS method was applied to the determination of PCDDs and PCDFs in human and fish tissues. Limits of quantification were about 1 pg/g of fat for all seventeen 2378 PCDD/Fs tested (starting amount of fat, 2 g).
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  • 48
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    Electronic Resource
    Weinheim : Wiley-Blackwell
    ISSN: 0935-6304
    Keywords: HPLC separation ; lucidin ; Rubia tinctorum ; anthraquinones ; isocratic elution ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---An HPLC method has been developed for the separation of anthraquinones with particular attention to the determination of lucidin in commercially available sources of Rubia tinctorum aglycones. Variations of chromatographic conditions have been studied in order to provide suitable resolution of anthraquinones under isocratic conditions on an end-capped RP C18-column.
    Additional Material: 2 Ill.
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  • 49
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    Electronic Resource
    Weinheim : Wiley-Blackwell
    ISSN: 0935-6304
    Keywords: Solvation parameter model ; ystem constants for poly(dimethyldiphenylsiloxane) HP-5 and poly(ethylene glycol) HP-INNOWax stationary phases ; temperature ; molecular interaction ; retention models ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---No abstract
    Additional Material: 1 Ill.
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  • 50
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    Electronic Resource
    Weinheim : Wiley-Blackwell
    ISSN: 0935-6304
    Keywords: On-line coupling HPLC/NMR ; HPLC/ESI-MS ; (2E,4Z)-decadienoic acid ; Agromyces spec ; isolation ; structure elucidation ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---No abstract
    Additional Material: 4 Ill.
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  • 51
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    Electronic Resource
    Weinheim : Wiley-Blackwell
    ISSN: 0935-6304
    Keywords: Enantiomer separation ; mixed chiral selectors ; modified cyclodextrins ; gas chromatography ; PCB ; o,p´-DDD ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Columns containing different types of cyclodextrin derivatives have been evaluated for chiral gas chromatographic separation of atropisomeric PCBs, o,p´-DDT and o,p´-DDD. Separation was attempted on columns containing mixed chiral selectors, and the performance of two closely related selectors was also examined. The cyclodextrins were: permethylated-β-CD (PM-β-CD), heptakis(2,3-di-O-methyl-6-O-tert-butyldimethylsilyl)-β-CD (2,3-M-6-TBDMS-β-CD), heptakis(2,3-di-O-methyl-6-O-tert-hexyldimethylsilyl)-β-CD (2,3-M-6-THDMS-β-CD), and heptakis(2,3-di-O-ethyl-6-O-tert-hexyldimethylsilyl)-β-cyclodextrin (2,3-E-6-THDMS-β-CD). The cyclodextrins were dissolved in OV-1701 or in a dimethylsiloxane/silarylene copolymer containing 5% phenyl in the backbone. The application of mixed chiral selectors led to improved separations, however; at most eleven PCB congeners were separated on a single column. Chiral resolution of o,p´-DDD was achieved. The use of a dimethylsiloxane/silarylene copolymer as a matrix for the cyclodextrins is a promising approach. With such a matrix, blocking of the CD cavities by silicone substituent groups can be avoided, and a reasonable CD solubility can be provided. The selectivity of heptakis(2,3-di-O-ethyl-6-O-tert-hexyldimethylsilyl)-β-CD and heptakis(2,3-di-O-methyl-6-O-tert-hexyldimethylsilyl)-β-CD was quite different, the former selector could separate four congeners, while the latter separated ten congeners.
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  • 52
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    Electronic Resource
    Weinheim : Wiley-Blackwell
    ISSN: 0935-6304
    Keywords: HPLC ; fast separation ; flavan-3-ol ; flavonols ; vegetables ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---A fast high-performance liquid chromatography method was used for analysis of prominent flavan-3-ols and flavonols in vegetables. Gradient elution with phosphoric acid-acetonitrile mixtures and phosphoric acid-methanol mixtures allowed fast and complete separation of the studied phenolic compounds within analysis times less than 10 min. The development of two elution gradients using methanol and acetonitrile as modifiers proved to be an excellent approach for the verification of the real polyphenolic composition in vegetables samples because the two optimized methods allowed the separation of the same number of compounds in the same elution order. Diode-array detection was employed for the provisional identification of phenolic compounds that were not available as standards. We preferred methanol as a modifier because it was less toxic and cheaper than acetonitrile. Detection limits ranged between 0.12 and 0.59 μg mL-1. High recoveries of phenolics from fresh vegetables were measured in all studied cases, independent of the phenolic structure, matrix, and vegetable in question. High levels of procyanidins between 150 and 450 mg kg-1 were found in all studied vegetables. Quantification of quercetin and kaempferol glycosides was only possible in marrow and onion, respectively.
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  • 53
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    Weinheim : Wiley-Blackwell
    ISSN: 0935-6304
    Keywords: Stir Bar Sorptive Extraction (SBSE) ; thermal desorption (TD) ; capillary GC-MS ; benzoic acid ; beverages ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Stir Bar Sorptive Extraction (SBSE), a recently introduced solventless extraction technique, was applied for the enrichment of benzoic acid in lemon flavored beverages. The stir bar is covered with 50 mg polydimethylsiloxane (PDMS) and the extraction mechanism is similar to that of solid phase micro extraction (SPME) but the enrichment factor is ca. 100 times higher. SBSE is followed by thermal desorption (TD)-capillary gas chromatography (CGC)-mass spectroscopy (MS). Calibration graphs for benzoic acid were linear from 1 to 1000 ppm for water and diluted soft drinks and the repeatability (n = 6) was less than 5% RSD.
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  • 54
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    Weinheim : Wiley-Blackwell
    ISSN: 0935-6304
    Keywords: Capillary GC ; fast GC ; on-column injection ; narrow-bore column ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---In this work a fast gas chromatography set-up with on-column injection was optimized and evaluated with a model mixture of C8-C28 n-alkanes. Usual injection volumes when using narrow-bore (e. g., 0.1 mm i.d.) analytical columns are ca. 0.1 μL. The presented configuration allows introduction of 10-30-fold larger sample volumes without any distortion of peak shapes. In the set-up a normal-bore retention gap (1 m×0.32 mm i. d.) was coupled to a narrow-bore (4.8 m×0.1 mm i. d.×0.4 μm film thickness) analytical column using a low dead volume column connector. The effects of the experimental conditions such as inlet pressure, sample volume, initial injection temperature, and oven temperature on a peak focusing are discussed. H-u curves for helium and hydrogen are used to compare their suitability for high speed gas chromatography and to show the dependence of separation efficiency on the carrier gas velocity at high inlet pressures. In the fast gas chromatography system a baseline separation of C10-C28 n-alkanes was achieved in less than 3 minutes.
    Additional Material: 4 Ill.
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  • 55
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    ISSN: 0935-6304
    Keywords: Comprehensive two-dimensional gas chromatography ; GC×GC ; thermal modulation ; oil analysis ; petroleum analysis ; analysis of middle-distillate oil fractions ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Comprehensive two-dimensional gas chromatography (GC×GC) is an utterly suitable separation technique for the analysis of complex samples, such as oil fractions. Once the two columns and the operating conditions are properly tuned, the technique is able to provide a detailed characterization of such materials. Some considerations applying to the tuning of a GC×GC system for a specific separation are presented and discussed. The authors present a number of different column sets and conditions which allow the separation of a non-aromatic hydrocarbon solvent, a kerosene, the light end of a crude oil, and an olefinic fraction, respectively. The highly structured GC×GC chromatograms, together with chemical knowledge about the samples, provide a much more comprehensive characterization of the samples than hitherto possible.
    Additional Material: 7 Ill.
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  • 56
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    ISSN: 0935-6304
    Keywords: Comprehensive two-dimensional gas chromatography ; thermal desorption modulator ; temperature programming ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---In comprehensive two-dimensional gas chromatography, two individual separations are coupled by means of a rotating thermal desorption modulator interface. The injection pulse introduced via the interface onto the second column should be as short as possible. Parameters affecting the modulator operation are studied. In the set-up used in this study, the temperature of the second column can be programmed independently from that of the first column. Optimization of the second-dimension separation to minimize peak broadening and maximize resolution is discussed and an elegant approach to determine second-dimension retention times using a non-constant modulation frequency is demonstrated. The high separation power of the comprehensive system is demonstrated by the analysis of technical and biota samples containing chlorinated biphenyls and toxaphene.
    Additional Material: 7 Ill.
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  • 57
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    ISSN: 0935-6304
    Keywords: Comprehensive two-dimensional GC ; GC×GC ; orthogonal chromatography ; GC/MS ; group type separations ; PCBs ; petroleum ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---The writer of this review published in 1978 a three-part article on two-dimensional gas chromatography in the first three issues of this journal [1]. The review was written at a time when capillary column GC was still in its infancy. Commercial columns were (essentially) unavailable and sample introduction into capillary columns was done exclusively in the split mode. Two-dimensional separations were explored in only a few laboratories. The limitations of capillary column technology made this exercise rather difficult. The introduction of fused silica capillary columns in the early eighties drastically changed the landscape in which gas chromatography was practiced. It took the chromatographic community just a few years to convert from packed columns to capillary columns. Instrumentation and accessories specifically designed for capillary column use came onto the market. This writer had great hopes that the revolution in capillary column GC would be mirrored in the development of instrumentation for Two-Dimensional Gas Chromatography. This never materialized. On the contrary, tentative steps taken by a few manufacturers and suppliers of chromatographic equipment fizzled out. It was perhaps the introduction of relatively inexpensive and user friendly GC/MS instrumentation, in combination with nearly indestructible fused silica capillary columns that took away the incentive to develop commercially viable Two-Dimensional Gas Chromatography. Much of the thinking went like this: why insist on good chromatography if mass spectrometry can do the job without the need of complete separation. Some progress in the further development of conventional Two-Dimensional Gas Chromatography has certainly been made over the last 20 years but there has not been a great deal of excitement. Applications have also been relatively sparse and they are limited to just a few areas. Science does not remain static and chromatography is no exception. Progress in gas chromatography is driven by new technology and ideas. Substantial improvements in two-dimensional GC were not forthcoming until Phillips and his research group introduced and implemented an entirely new form of Two-Dimensional Gas Chromatography, called comprehensive GC×GC. This breakthrough occurred only in 1991 [2]. It does take some time before scientists change attitudes and habits. There is always a time lag between the introduction of new technology and its general acceptance. The public's attitude toward comprehensive Two-Dimensional Gas Chromatography is probably no exception. The number of scientists who are actively pursuing this new branch of gas chromatography is still very small. It is often a single individual who carries the torch. J.B. Phillips' name is synonymous with comprehensive Two-Dimensional Gas Chromatography. He is not only its inventor and proponent but his fertile mind has initiated research in other related areas. Sadly, he passed aware shortly before this review was written. This contribution is dedicated to his memory.
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  • 58
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    ISSN: 0935-6304
    Keywords: Multidimensional gas chromatography ; comprehensive two-dimensional gas chromatography ; GC×GC ; oxygenates ; MTBE ; reformulated gasoline ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Comprehensive two-dimensional gas chromatography (GC×GC) has been applied to the quantitation of oxygenates in reformulated gasoline. Target oxygenates were C1-C4 alcohols, tert-pentanol, methyl tert-butyl ether (MTBE), diisopropyl ether (DIPE), ethyl tert-butyl ether (ETBE), and tert-amyl methyl ether (TAME). These were separated from the gasoline matrix using a volatility-based selectivity in the first chromatographic dimension, followed by a mixed-phase polarity/shape selectivity in the second dimension. The high resolving power of this stationary phase combination completely separated all oxygenates except DIPE, ETBE, and TAME, which exhibited coelution with other nonpolar gasoline components. Oxygenates quantitation was achieved with the use of an internal standard, an FID detector, and calibration curves. Quantitation results are in good agreement with ASTM and EPA standard methods. When coupled with our previous method for BTEX and aromatics, a single GC×GC method can now quantitate MTBE, alcohols, BTEX, and aromatics in a one-hour analysis.
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  • 59
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    ISSN: 0935-6304
    Keywords: GC×GC ; comprehensive two-dimensional GC ; thermal modulation ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---A jet of cool gas is used to locally cool a section of modulator tube in the presence of the stirred oven bath of a GC×GC instrument. Local cooling decouples the temperature of the modulator tube from that of the first dimension column, which was 100 meters long. Overall resolution of the GC×GC experiment was improved as a result. Another consequence of the jet-cooled thermal modulation structure is the elimination of moving parts in the GC oven. By pulsing cold and hot jets of gas onto a modulator tube with solenoid valves, two stage thermal modulation can be obtained without the complexity of moving parts in the vicinity of the capillary columns.
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  • 60
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    ISSN: 0935-6304
    Keywords: GC×GC ; thermal modulation ; comprehensive three-dimensional GC ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Comprehensive three-dimensional gas chromatography (GC3) is demonstrated using modified GC×GC apparatus. A new thermal modulation scheme employing a single moving heater to operate two thermal modulators is introduced. Considerations of the bandwidth/resolution tradeoff of GC3 show that high-speed tertiary columns would make GC3 practical, with modest loss of underlying GC×GC peak capacity.
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  • 61
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    ISSN: 0935-6304
    Keywords: Spearmint ; peppermint ; GC×GC ; essential oils ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---This paper investigates the separation of moderately complex samples by comprehensive two-dimensional gas chromatography (GC×GC). The analysis of peppermint (Mentha piperita) and spearmint (Mentha spicata) essential oil components, including acetates, alcohols, furans, ketones, sesquiterpenes, and terpenes, was achieved by one-dimensional gas chromatography with quadrupole mass spectrometry detection (GC/MSD) and GC×GC with flame ionization detection. Peppermint essential oil was found to contain 89 identifiable peaks by GC×GC compared to 30 peaks in the GC/MSD chromatogram. Likewise, 68 peaks were found in the GC×GC chromatogram of spearmint (compared to 28 in GC/MSD). Plots of the first dimension versus second dimension retention times provided a fingerprint of the two essential oils, which revealed 52 similar compounds between the two essential oils as opposed to 18 matches by 1D GC.
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  • 62
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    ISSN: 0935-6304
    Keywords: Capillary electrophoresis ; UV detection ; organic acids ; background electrolyte optimization ; wine ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---A simple technique is described for the routine capillary electrophoretic determination of organic acids in wine samples. Several aromatic and non-aromatic compounds, including phthalic acid, benzoic acid, sorbic acid, boric acid, and phosphate, were evaluated as background electrolytes in order to obtain the highest resolution and detection sensivity. Factors that affect capillary electrophoretic separation such as the concentration and pH of the background electrolyte (BGE), the concentration of the electroosmotic flow modifier (EOF), and methanol addition to the electrolyte were investigated systematically. Tartaric, malic, succinic, acetic, and lactic acids were determined simultaneously in approximately six minutes using an electrolyte containing 3 mM phosphate and 0.5 mM myristyltrimethylammonium bromide (MTAB) as electroosmotic flow modifier at pH 6.5. This method is quantitative, with recoveries in the 90-102% range and linear up to 50 mg L-1. The precision is better than 1% and the procedure shows the appropriate sensibility, with detection limits between 0.015 and 0.054 mg L-1. The proposed method was successfully employed for the determination of organic acids in wine samples by direct sample injection after appropriate dilution and filtration.
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  • 63
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    ISSN: 0935-6304
    Keywords: Capillary electrophoresis (CE) ; laser induced fluorescence detection (LIFD) ; fluorescein isothiocyanate (FITC) ; inulin ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---No abstract
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