Influence of some inorganic salts on the polarity of apolar polymer phases in capillary gas chromatography

Different stationary phases were prepared by mixing a series of inorganic salts with dimethylsiloxane polymer (SE-30) and then tested by capillary gas chromatography. It was demonstrated that the polarity (as evaluated by measurement of Rohrschneider constants) of the mixed stationary phases, which is inferior or equal to that of a medium-polar OV-25 phases, reached even lower values than SE-30 alone. The influence of NaF, NaCl, NaBr, AgNO₃, and other inorganic salts on the polarity of capillaries is reflected by a better resolution and shorter retention time of cis/trans isomers of fatty acid methyl esters (FAMES) as well as positional isomers of triglycerides.     

Enantiomer separation of 2-halocarboxylic acid esters by chiral complexation gas chromatography

The enantiomer separation of 2-halocarboxylic acid esters on two chiral nickel(II) bis-((perfluoroacyl)terpeneketonates) by complexation gas chromatography is described. The quantitative entiomer separation of branched 2-halocarboxylic acid esters is achieved with nickel (II) bis (3-(heptafluorobutanoyl)(1R, 2S)-pinan-4-onate) 1 while unbranched 2-halocarboxylic acid esters are preferably separated on nickel(II) bis(3-(heptafluorobutanoyl)-(1S)-10-methylenecamphorate) 2. The metal chelates 1 and 2 are accessible in both enantiomeric forms allowing the determination of the enantiomeric excess (ee) effective and reliable.     

Characterization of Saccharomyces Sp. through determination of amino acid profiles by capillary gas chromatography

The Saccharomyces strains uvarum, montuliensis, bayanus, capensis and florentinus were grown in liquid media prepared from a 1% aqueous glucose solution to which 0.05% of ammonium sulfate or urea were added as the only nitrogen supply. The amino acids exuded during incubation were isolated by cation exchange and derivatized as the corresponding N,O-heptafluorobutyryl isopropyl esters. Separation was achieved on a highly deactivated glass capillary column coated with OV-101. A characteristic amino acid profile was obtained for each of the species studied, allowing the construction of a chemotaxonomic tree, on the basis of present or absent acids.     

Determination of amino acid enantiomers in orange juices by chiral phase capillary gas chromatography

Summary The configurations of free amino acids (AAs) in orange juice beverages (commercial products of satisfactory and unsatisfactory quality), an orange juice concentrate (bulk product suspected of being adulterated), and in an orange juice that has been contaminated by addition ofLactobacillus plantarum as a model for microbial spoilage, were determined, after derivatization, by means of gas-liquid chromatography (GC) using fused-silica capillary columns coated with Chirasil-L-Val or Chirasil-D-Val as stationary phases. AAs were isolated from juices by treatment with Dowex WX8 ion-exchanger and were investigated, by GC, as theirN(O)-pentafluoropropionylorN(O)-trifluoroacetyl 1-propyl esters. It was found that the high quality orange juice beverage contained L-AAs exclusively whereas this juice, after fermentation withLactobacillus, contained free D-Ala (32.7%), D-Val (62.3%), D-Phe (20.0%), D-Glu (24.3%), D-Ser (2.6%), D-Asp (0.8%), and significant amounts of D-Pro [% D=100 D/(D+L)]. D-Ala (8.8%) and D-Ser (4.2%) were found in a sensory and analytically unsatisfactory orange juice beverage, whilst D-Ala (27.5%) and D-Ser (14.3%) were detected in the orange juice concentrate suspected of being adulterated.Although capillary GC on chiral stationary phases is regarded as being highly suitable for the determination of AA enantiomers in fruit juice beverages, detection of D-AAs is currently not considered as conclusive proof of fruit juice adulteration caused by addition of AA racemates since a non-microbial origin of D-AAs in the respective juice, or an original occurrence of D-AAs, in either the free, substituted, or peptide-bonded form in the fruits, cannot be excluded with certainty.Presented in part at the Deutscher Lebensmittelchemikertag, Sept. 18–21, 1990, Frankfurt and at the 14. Jahrestagung Deutscher Lebensmitteltechnologen, Nov. 15–17, 1990, Düsseldorf.     

Practical limitations of capillary gas chromatography

Glass capillary gas chromatography is a high resolution separation method which allows the qualitative and quantitative analysis of even complex mixtures, which may contain many components–also isomeric–in a wide range of volatilities, polarities and concentrations. The principal limitation of gas chromatographic application is given by an insufficient volatility of the species to be separated. Elevated temperatures have to be applied if the application range is to be extended and to achieve steep peak profiles, i.e. low detection limits at high resolution. The use of elevated temperatures is limited, of course, by the temperature stability of both the solvent (stationary liquid and support) and the solutes. The problems of trace analysis for low volatility compounds at high resolution and its limitational parameters regarding sampling, separation and detection are discussed. The applicability of glass capillary columns in this field is influenced by the following parameters: tailing behaviour; irreversible adsorption of polar and decomposition of unstable solutes; thermal stability of stationary liquid (including the support deactivation); separation efficiency and sample capacity (film thickness). Multidimensional gas chromatography using capillary columns coupled either with a packed or another capilllary column for preseparations may be applied with advantage in the analysis of complex mixtures.     

Glass capillary gas chromatography with simultaneous flame ionization (FID) and Hall® element-specific (HECD) detection

Two glass capillary gas chromatographic systems were equipped with inert effluent splitters which allowed simultaneous data acquisition using nonspecific and element-specific detectors. Simultaneous detection was achieved using the nonspecific flame ionization detector (FID) and the Hall^® electrolytic conductivity detector (HECD) operated in either the sulfur-or the nitrogen-specific mode. Typical application of the simultaneous detection system as applied to analysis of petroleum residues is briefly described. The Hall electrolytic conductivity detector can be made element specific for halogen-, sulfur-, or nitrogen-containing compounds. Simultaneous detection enhances the information yield from a single sample injection and proves to be a powerful complementary technique when used with computerized gas chromatography/mass spectrometry.     

Gas-liquid chromatography of amino acids: Columns and methodology as a basis for routine amino acid analysis using glass capillary gas chromatography

A carefully Standardized technique is described for the preparation of glass capillary columns which can be used successfully for routine quantitative amino acid analysis. Comparison is made between two different modes of sample injection. Preliminary quantitative results from “split” injection and “on-column” injection techniques are evaluated statistically and it is concluded that the “on-column” system is a prerequisite for quantitative amino acid analysis by glass capillary gas chromatography. An analysis of fish muscle protein hydrolyzate illustrates an application of this technique and results are compared with those from a packed column analysis.     

Rapid on-line analysis of low molecular weight hydrocarbons using glass capillary gas chromatography

Rapid analysis is important for on-line chromatography. Gaseous or vaporized samples have been injected via heated gas sampling valves of less than 500 μl dead volume. The critical sampling and split problems could be solved by temperature programming. The general analysis described could be successfully used inter alia in scouting reactions.     

Separation of pesticides by capillary gas chromatography. Part 1: s-Triazines and substituted urea herbicides

The authors have shown that capillary columns are perfectly adequate for the separation of s-triazine herbicides and urea herbicides. The method presented remains adequate when the initial molecules are accompanied by some of their metabolites.     

Glass capillary columns for separation of free organic acids

Glass capillary columns have been prepared without acidic additive in the stationary phase, from which free organic acids elute as sharp and symmetrical peaks. The required surface in the borosilicate glass capillary was generated by a combination of leaching with aqueous HCl and deposition of colloidal silica particles; it can be coated with stationary phases have a broad range of polarity. Aqueous samples containing free organic acids can also be analyzed in such columns in an isothermal mode.     

On-line hydrogenation of fatty acid methyl esters in capillary gas chromatography

An injection splitter in front of a glass capillary column was used for the hydrogenation of fatty acid methyl esters (FAME) mixtures. Hydrogenation followed by gas chromatographic analysis on capillary columns permitted detection and identification in complicated natural mixtures of branched fatty acids, showing minor structural differences, in quantities down to 10^?8g. The technique described, apart from its suitability for FAME analysis, shows promise for structure determination studies of other classes of compounds.     

Trace analysis of fungicides in grape juice and wine using glass capillary gas chromatography

The fungicides Bupirimate, Fenarimol, and Vinclozolin were sprayed on Vines. The fruits were harvested 8 and 21 days after the final application and processed to juice and wine. The fungicide residues were determined by filtration of the samples throug XAD-2 after pH adjustment, elution with methylene chloride, and glass capillary gas chromatography with SE-30 as stationary phase. Residue values of the three compounds were reported before and after fermentation. The precision of the analytical method was established by spiking portuguese white wine and spanish grape juice with the three fungicides and Triadimefon. The recoveries were in the range 80%-100%, except for Vinclozolin.     

High resolution glass capillary columns for the gas chromatographic analysis of alditol acetates of neutral and amino sugars

The development of improved high resolulation glass capillary columns for separating the alditol acetates of neutral and amino sugars is described. Different capillary column treatments were evaluated for their activity toward amino sugar derivatives and for their effect on the efficiency of the completed column. The simple two-step procedure of leaching with aqueous hydrochloric acid and dynamic coating with SP-2330 was found to produce efficient and inert columns.     

Identification and quantitation of trace amounts of barbiturates with glass capillary gas chromatography

Pre-chromatographic reactions are no longer a necessary evil. Equipment such as the microrefluxer now allows reproducible 7-μl-reactions to be carried out in a short time. Thus multiple derivatisations can be used together with glass capillary GC for routine identifications. The method has been succesfully applied to barbiturates. Retention data of their methyl-, allyl- and benzyl-derivatives are given. Quantitative blood level determinations are briefly discussed.     

Residue analysis of organophosphorus pesticides in food with two-dimensional gas chromatography using capillary columns and flame photometric detection

Two-dimensional gas chromatography with two capillary columns of different polarity (SP 2100 and OV 225) is used for pesticide residue analysis in food samples. By means of “live chromatography” applying pneumatic switching technique according to Deans, unequivocal identification of 57 organophosphorus pesticides in food samples is achieved at trace concentrations. The instrument is equipped with only one injection port and one flame photometric detector. On-line data processing is very helpful, especially in calibration and checking the system's reliability with the multitude of test compounds. The complete pesticide residue analysis including clean-up of about six food samples can be completed by one person in 8 hours.