Some aspects of quantification of neutral steroid metabolites in body fluids of healthy and uremic subjects by capillary gas chromatography

Neutral steroid metabolites enriched from urine and hemofiltrate were identified by gas chromatography/mass spectrometry and quantified by capillary gas chromatography. This study included 20 healthy controls and 37 uremic patients. Before enrichment of steroids from biological material, the standard deviation of the workup procedure and subsequent derivatization into the trimethylsilyl-enol-trimethylsilyl ethers was tested and found to be 2–5% in urine and 12–17% in the more complicated workup procedure of hemofiltrate, but essentially smaller than the biological standard deviation. Compared to the 24 h urinary excretion rates of controls, the excretion rates of androsterone, etiocholanolone, and corticoid metabolites were significantly lower in uremic body fluids, while those of 11-oxygenated androstanolones, degradation products of corticoids, were enhanced in uremic urine. The ratio of corticoid metabolites to 11-oxygenated androstanolones in urine of nondialyzed uremics correlated significantly with their plasma creatinine levels.     

High resolution gas chromatography of tobacco smoke: The contributions of kurt grob

The contributions made by Kurt Grob to tobacco science are reviewed with emphasis on the application of high resolution gas chromatography to tobacco smoke analysis. Highlighted are his pioneering achievements in the preparation and use of glass capillary columns, GC-MS, and splitless injection.     

Analysis of chemically modified polystyrenes with pyrolysis-capillary gas chromatography

Pyrolysis-capillary GC has been applied to the analysis of chemically derivatized polystyrenes. The reproducibility of the method and the influence of instrumentation has been discussed.     

Enantiomer and diastereomer resolution of dipeptides by gas chromatography on chirasil-val

Several dipeptides have been separated into stereoisomers (enantiomers, diastereoisomers, sequential isomers) by GC on the chiral stationary phase Chirasil-Val. Sufficiently volatile N-TFA-dipeptide methyl esters have been formed by derivatization at ambient temperature, thus avoiding racemization (or epimerization, respectively), and peptide cleavage. This novel approach has proven particularly useful for the determination of stereoisomeric composition of dipeptides in biological fluids.     

The application of high performance liquid chromatography, coupled to nuclear magnetic resonance spectroscopy and mass spectrometry (HPLC-NMR-MS), to the characterisation of ibuprofen metabolites from human urine

Summary The use of HPLC-NMR-MS for the detection and identification of the metabolites of ibuprofen present in a solid phase extract of human urine is described. Gradient reversed-phase HPLC was used to separate the components present in the extract, which were then characterised by a combination of stopped-flow¹H NMR and on line electrospray-MS. This approach led to the rapid identification of the known phase 1 human metabolites of ibuprofen, including hydroxy- and carboxy- metabolites, together with their respective glucuronide conjugates. In addition a probable artefact resulting from the dehydration of one of the side chainhydroxylated glucuronides was also identified.     

Enzyme activity determination by radio gas chromatography on capillary columns

Androgen 5α-reductase from the foreskin of 48 boys in prepubertal age was analyzed by evaluation of the apparent K_m-and V_max- values after tissue incubation. Reaction rates were calculated after determination of specific radioactivity of distinct metabolites, by comparison to the radioactivity of the precursor. Reaction products were separated by radio gas chromatography on capillary columns. The chromatography system was based on multicolumn equipment with column switching facilities and a variable splitter at the outlet of the separation column. A radioactivity monitor (gas proportional counter) was used for measurement of radioactivity in the column effluents. An electron capture detector was used for mass detection of steroid acyl derivatives.     

Analysis of essential oils by direct sampling from plant secretory structures and capillary gas chromatography

It is of fundamental importance to know the true composition of the essential oil produced by the secretory structures of a plant, both from a biogenetic and a chemotaxonomic point of view. This paper considers a method which combines direct sampling with on-column CGC and studies the oils directly from the secretory structures: some examples are given (Humulus lupulus L., Tagetes erecta L., and Tagetes patula L.). For each plant, the composition of the distilled oil is compared to that obtained by direct sampling, and a photograph of the secretory structures taken by electroscanning microscopy is given.     

Simultaneous coupling of capillary supercritical fluid chromatography and high temperature glass capillary gas chromatography to a mass spectrometer

The coupling of glass capillary supercritical fluid chromatography to a high temperature GC/MS system via a micrometeradjustable glass capillary interface including an integrated pressure restrictor is described. With this coupling device, both complementary capillary chromatographic methods retain their full independence and flexibility. It is shown that in supercritical fluid chromatography glass fulfils all the requirements of a suitable support material. The preparation of narrow bore glass capillary columns (0.06 mm i.d.), coated with chemically bonded and crosslinked fluids with a film thickness of about 0.6 μm, which exploit the merits of OHterminated polysiloxanes as stationary phases is discussed. The application of glass capillary SFC is demonstrated and compared with examples given in the literature.     

Some applications of capillary gas chromatography in the chemical industry

About three years ago, fused silica capillary columns were introduced in the Quality Control Laboratory of the Shell refinery/chemical complex at Pernis. In general, long, thick-film, wide-bore capillary columns are used together with low split ratios and hydrogen as carrier gas. These conditions enable the analysis of relatively large sample amounts, resulting in low detection limits for the minor components without overloading by the major components, while still maintaining a satisfactory resolution. A number of applications are shown, such as the analysis of complex mixtures, the determination of trace impurities and the analysis of residual volatiles in polymers.     

On-line multidimensional chromatography using packed capillary liquid chromatography and capillary gas chromatography

The introduction of selected fractions from a liquid chromatograph into a gas chromatograph has been described; however, analyses were performed by off-line experiments requiring collection and reinjection of the separate fractions or by on-line procedures where disadvantageously, only a fraction of the separated peak or a well resolved component in a mixture could be introduced into a gas chromatograph. This disadvantage is overcome by the apparatus and method described in this paper, which utilizes a multidimensional chromatography system employing a high efficiency, packed capillary LC column coupled on-line to a capillary gas chromatograph. The liquid chromatograph (so designed) can act as a highly efficient clean-up or chemical class fractionation step prior to introduction into the gas chromatograph, significantly reducing sample preparation times in many applications. Thus minor components in a complex matrix can be determined without prior sample clean-up, an example of which is the determination of polychlorinated biphenyls in a complex hydrocarbon matrix.     

Comparative chemical analysis of commercial creosotes and solvent refined coal-II materials by high resolution gas chromatography

The chemical composition of a commercially available creosote was compared to a direct coal liquefaction product, i.e., solvent refined coal-II fuel oil blend (SRC-II FOB) using high resolution gas chromatography (HRGC). In addition, hydrogenated products of these materials were studied. Samples were fractionated by chemical class on neutral alumina. Those fractions previously shown to be the most mutagenic and tumorigenic in laboratory bioassays of coal-derived materials were analyzed and compared by HRGC and gas chromatography/mass spectrometry (GC/MS). Individual components were tentatively identified and quantitated. Although similar chemical components were present in the creosote and SRC-II FOB fractions studied, the creosotes had higher concentrations of heavy molecular weight materials and a lower ratio of alkylated to parent polycyclic aromatic compounds than the coal liquefaction products. The creosote samples also had a significantly higher concentration of components which eluted in the polycyclic aromatic hydrocarbon (PAH) chemical class fraction. Amino-substituted PAH were present in both nonhydrogenated coal liquid and creosote materials. The creosote and SRC-II FOB crudes and nitrogen-containing polycyclic aromatic compound (NPAC) chemical class fractions expressed similar microbial mutagenicity. Based on chemical analysis data, the predicted tumorigenic potency of the creosote in laboratory bioassay systems would be equivalent to or greater than the SRC-II FOB.     

Feasibility of ultra-high performance liquid and gas chromatography coupled to mass spectrometry for accurate determination of primary and secondary phthalate metabolites in urine samples

Phthalates (PAEs) are ubiquitous toxic chemical compounds. During the last few years, some phthalate metabolites (MPAEs) have been proposed as appropriate biomarkers in human urine samples to determine PAE human intake and exposure. So, it is necessary to have fast, easy, robust and validated analytical methods to determine selected MPAEs in urine human samples. Two different instrumental methods based on gas (GC) and ultra-high performance liquid (UHPLC) chromatography coupled to mass spectrometry (MS) have been optimized, characterized and validated for the simultaneous determination of nine primary and secondary phthalate metabolites in urine samples. Both instrumental methods have similar sensitivity (detection limits ranged from 0.03 to 8.89 pg μL⁻¹ and from 0.06 to 0.49 pg μL⁻¹ in GC–MS and UHPLC–MS², respectively), precision (repeatability, expressed as relative standard deviation, which was lower than 8.4% in both systems, except for 5OH-MEHP in the case of GC–MS) and accuracy. But some advantages of the UHPLC–MS² method, such as more selectivity and lower time in the chromatographic runs (6.8 min vs. 28.5 min), have caused the UHPLC–MS² method to be chosen to analyze the twenty one human urine samples from the general Spanish population. Regarding these samples, MEP showed the highest median concentration (68.6 μg L⁻¹), followed by MiBP (23.3 μg L⁻¹), 5cx-MEPP (22.5 μg L⁻¹) and MBP (19.3 μg L⁻¹). MMP (6.99 μg L⁻¹), 5oxo-MEHP (6.15 μg L⁻¹), 5OH-MEHP (5.30 μg L⁻¹) and MEHP (4.40 μg L⁻¹) showed intermediate levels. Finally, the lowest levels were found for MBzP (2.55 μg L⁻¹). These data are within the same order of magnitude as those found in other similar populations.     

Direct enantiomer resolution of primary,secondary, and tertiary alcohols by gas chromatography on Chirasil-Val

Summary Many enantiomeric pairs of alcohols (primary, secondary or tertiary) are resolved directly on persilylated glass capillary columns, coated with the chiral stationary phase L- or D-Chirasil-Val. Dependent on the chemical structure of the substrate, considerable resolution factors can be obtained, even with simple aliphatic alcohols. Thus, one strong attraction may be sufficient to produce significant chiral recognition. Enantiomeric purities of these alcohols can be determined with high accuracy and great ease.     

High resolution gas chromatographic determination of permanent gases with a helium ionization detector

The capability of the helium ionization detector (HID) to operate in connection with capillary columns for trace gas analyses has been evaluated. Two different capillary columns were considered: a PLOT fused silica column with molecular sleve and a thick film WCOT glass column with PS-255. The determination of trace impurities in gases can be achieved with evident advantages over classical adsorption columns, even using a split injection system. Direct on-column injections also have been investigated with promising results.     

Advantage of the universal equation over the linear equation for the calculation of retention parameters of homologous series in capillary chromatography

A procedure is suggested for preparation of reproducible and stable galss capillary Apiezon LH+KF columns for the determination of organic compounds containing different functional groups. The advantage of the universal equation over the linear equation for calculation of retention indices for any homologs, including the first members of the series, is shown using the following five homologous series as examples: fatty acid methyl esters, methyl ketones, secondary and tertiary aliphatic amines, and N-alkyl piperidines. The accuracy of the calculation enables the universal equation to be used in computer-assisted identification.     

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.