Combined Use Of Gas Chromatography Research Articles

Comparison of Potent Odorants in Traditional and Modern Types of Chinese Xiaoqu Liquor (Baijiu) Based on Odor Activity Values and Multivariate Analyses.

Predominant odorants in modern and traditional types of Chinese xiaoqu liquor (Baijiu) were identified and compared by the combined use of gas chromatography−olfactometry, odor activity values (OAVs), and multivariate analyses. A total of 79 aroma compounds were identified in a typical modern type xiaoqu Baijiu (M) and a typical traditional type xiaoqu Baijiu (T), 42 of them had OAV > 1 in both M and T samples. The main differences between the two samples were obtained for the concentration of 23 aroma-active compounds. A total of 22 samples made by different brewing processes were analyzed to confirm the differences. Partial least squares discriminant analysis confirmed that 20 compounds could be used as potential markers for discrimination between modern type xiaoqu Baijiu and traditional type xiaoqu Baijiu. Their difference in content is between 1.5 and 17.9 times for modern type xiaoqu Baijiu and traditional type xiaoqu Baijiu. The results showed the aroma characteristics of modern and traditional type xiaoqu Baijiu clearly and comprehensively, which will provide guidance for modern Baijiu quality control and evaluation.

The combined use of GC, PDSC and FT-IR techniques to characterize fat extracted from commercial complete dry pet food for adult cats

AbstractThis study aims to compare the quality of fat extracted from different priced dry pet food for adult cats through classical and instrumental methods: pressure differential scanning calorimetry (PDSC), Fourier transform infrared spectroscopy (FT-IR) or gas chromatography (GC). Fat extracted from pet food was examined for induction time (IT), fatty acid composition, free fatty acid (FFA) content and peroxide value with the use of PDSC, GC, acid–base and iodometric titration, respectively. FT-IR data from the selected spectral regions correlate with the value of oxidation IT or the content of FFA. This resulted in construction of a reference model for IT with the following statistical features: Rcalibration = 0.917 (RMSEC = 28.0) and Rvalidation = 0.841 (RMSEP = 34.6). For fatty acid content, model statistics were as follows: Rcalibration = 0.912 (RMSEC = 0.61) and Rvalidation = 0.856 (RMSEP = 0.75). Discriminant model that uses spectral data alone, calculated with performance index 83.7 allowed distinguishing the studied pet food samples due to the price. Studies conducted proved PDSC and IR as reliable analytical techniques to control and monitor the quality of dry pet food for cats. Considering quality of the studied samples, it was proved that low-priced pet foods can be stored longer than premium-priced ones, while former is nutritionally more beneficial for adult cats.

Combined use of gas chromatography and HPLC-ESI-Q-TOF to assess the culinary uses of archaeological Santa María style ceramic vessels from El Colorado (Catamarca, Argentina)

In this paper, an interdisciplinary investigation was carried out to study if Santa Maria tricolor style vessels were used as culinary equipment in a 14th century ad domestic cooking space in El Colorado (Yocavil valley, Catamarca, Northwest Argentina) and to question the long-established idea that Santa Maria vessels were exclusively funerary objects. The combined use of gas chromatography (GC-FID), gas chromatography–mass spectrometry (GC-MS), and high-performance liquid chromatography coupled to electrospray ionization and quadrupole time-of-flight mass spectrometry (HPLC-ESI-Q-TOF) to study residual lipids from Santa Maria style vessels provided valuable information on their ancient use. Also, an ordinary striated style ceramic pot with distinct visible soot marks, as well as sediments from the cooking area, was studied for comparative purposes. Fatty acid, sterol, and acylglyceride profiles were characterized, and markers of food sources were searched in the complex mixtures. We identified intact triacylglycerides (TAGs) in the archaeological samples, even unsaturated, indicating exceptional preservation of lipids in the ceramic matrixes. Cholesterol or cholesterol oxidation products were observed in all ceramic containers, as well as plant sterols (stigmasterol, sitosterol) in two containers. Markers for ruminant lipids, such as TAGs that contain odd-chain fatty acids, were found, supported by the identification of odd-chain and branched-chain fatty acids with GC-FID and GC-MS. This evidence contributes to the hypothesis that Santa Maria vessels were used for culinary purposes in this archaeological domestic cooking space.

Comprehensive chemical profiling of Guizhi Fuling capsule by the combined use of gas chromatography–mass spectrometry with a deconvolution software and rapid‐resolution liquid chromatography quadrupole time‐of‐flight tandem mass spectrometry

Herbal formulations are complex natural mixtures. Researchers usually tend to focus more on analysis of nonvolatile components but pay less attention to volatile compounds. In this study, an analytical strategy combining two approaches was established for comprehensive analysis of herbal formulations. Guizhi Fuling capsule (GFC), a drug approved by the FDA to enter phase II clinical trial for treatment of primary dysmenorrhea, was taken as a case for analysis. Gas chromatography-mass spectrometry (GC-MS) with automated mass spectral deconvolution and identification system (AMDIS) led to rapid identification of 48 volatile components including four acetophenones, three fatty acid esters, 13 phenylpropanoids and 19 sesquiterpenes. Most of them were found from Guizhi. The volatile oils of Guizhi have been proved to exhibit many pharmacological activities. This is helpful in understanding the pharmacological mechanism of GFC. Furthermore, AMDIS turned out to be efficient and reliable for analysis of complex herbal formulations. Rapid-resolution liquid chromatography (RRLC) coupled with electrospray ionization quadrupole time-of-flight tandem mass spectrometry (ESI-Q-TOF MS/MS) allowed the identification of 70 nonvolatile components including six acetophenones, 12 galloyl glucoses, 31 monoterpene glycosides, three phenols and 12 triterpene acids. Fragmentation behaviors of assigned components, especially triterpene acids, which are hard to identify by low-resolution MS, were first investigated by TOF MS/MS. Characteristic ions and typical loss of assigned triterpene acids were summarized. Combinatorial use of GC-MS-AMDIS and RRLC-ESI-Q-TOF MS/MS could be of great help in global qualitative analysis of GFC, as well as other herbal products.

Combined Use of GC-TOF MS and UHPLC-(Q)TOF MS To Investigate the Presence of Nontarget Pollutants and Their Metabolites in a Case of Honeybee Poisoning

The combined use of gas chromatography (GC) and ultrahigh-pressure liquid chromatography (UHPLC), both coupled to time-of-flight mass spectrometry (TOF MS), has been explored in this work for the investigation of several cases of honeybee poisoning. The procedure applied involves a previous extraction with acetone followed by liquid-liquid extraction with dichloromethane. Both techniques, GC-TOF MS and UHPLC-(Q)TOF MS, have been applied to discover the presence of compounds that might be responsible of honeybee deaths. The application of a nontarget methodological approach to a first case of poisoning allowed the detection of the insecticide coumaphos at high concentration levels in the samples. The presence of possible metabolites of this organophosphorus insecticide was investigated by using both techniques. UHPLC-(Q)TOF MS showed its higher applicability in this case, as most of the metabolites were more polar than the parent compound. Four metabolites were identified by UHPLC-(Q)TOF MS, whereas only two of them were found by GC-TOF MS. The developed methodology was applied to other subsequent poisoning cases in which insecticides such as coumaphos, thiamethoxam, pyriproxyfen, and chlorfenvinphos were identified by both techniques, whereas GC-TOF MS also allowed the detection of fenitrothion and methiocarb. In all positive cases, the confirmation of the presence of the compound detected was feasible by means of accurate mass measurements of up to five ions together with their ion ratio evaluation.

Focus on Alcohol & Drug Abuse: Ensuring Validity in Urine Drug Testing

Focus on Alcohol & Drug Abuse: Ensuring Validity in Urine Drug Testing

Focus on Alcohol & Drug Abuse: Ensuring Validity in Urine Drug Testing

Methods for urine drug testing have been available for several decades. These procedures are useful in assessing and identifying substance use in treatment programs, research programs, law enforcement, the workplace, and schools. Despite widespread adoption of such techniques, limited knowledge exists regarding their valid use and interpretation among many who frequently perform these tests. This column discusses how obtaining a valid test result is a complex process because results are affected by several factors, including the substance of interest, test methodology, pharmacokinetics, chain-of-custody procedures, and intentional tampering.

Determination of pesticide residues in waters from small loughs by solid-phase extraction and combined use of gas chromatography with electron-capture and nitrogen-phosphorus detection and high-performance liquid chromatography with diode array detection

A procedure for the determination of pesticide residues in waters from small loughs surrounded by different crops has been developed. For this purpose, a solid-phase extraction procedure with octadecylsilane cartridges was used, optimizing the elution parameters as well as tthe breakthrough volume and the influence of the pesticide amount. The recoveries of the pesticides can be improved by about 10–20%. Extracts were analyzed either by gas chromatography with electron-capture and nitrogen-phosphorus detection or high-performance liquid chromatography with diode array detection to achieve a more reliable identification and determination of twenty-three pesticides from different chemical famiies, including triazines, phenylureas and organophosphorus.

BORNEOL AS AN ATTRACTANT FOR CYZENIS ALBICANS, A TACHINID PARASITOID OF THE WINTER MOTH, OPEROPHTERA BRUMATA L. (LEPIDOPTERA: GEOMETRIDAE)

AbstractVolatile compounds were isolated and identified from a crude extract of garry oak, Quercus garryana, foliage which was known to be attractive to the tachinid fly Cyzenis albicans. Candidate compounds were identified by the combined use of gas chromatography–mass spectrometry, and infra-red spectroscopy. Specific oak-leaf volatiles were field-tested in 2 different years in an apple orchard. Compounds were applied singly or in combination to individual apple trees; the number of C. albicans entering the canopy of each tree was observed and the number of eggs they oviposited on foliage was estimated. Borneol was the only compound that attracted flies when compared with the other treatments, but this did not result in more fly eggs being oviposited on borneol-treated trees. None of the compounds tested resulted in a greater number of Cyzenis eggs being oviposited. A greater abundance of borneol in oak foliage than in apple foliage, and its attractiveness to C. albicans, may explain the aggregation of flies in response to feeding-damage among oak trees and the absence of this pattern among apple trees.

A simple method for determination of heavy water by combined use of gas chromatography and platinum catalyst.

Since deuterium gas is different from hydrogen gas in thermal conductivity, the deuterium quantity of deuterated hydrogen HD can be determined with a thermal conductivity detector.HD is obtained by the isotopic exchange reaction between heavy water and hydrogen gas by means of a platinum catalyst.H2 (G) +HDO (L) _??_CatalystHD (G) +H2O (L)We developed a high activity platinum catalyst.A simple method for determination of heavy water was achieved by combined use of gas chromatography and platinum catalyst.After the isotopic reaction between sample heavy water HDO and hydrogen, the generated water is removed by molecular sieve. The deuterium quantity of the generated HD is measured by injecting it into a thermal conductivity detector of gas chromatograph under flowing carrier hydrogen gas, as the chromatogram.The value of coefficient of variation in the analytical results is less than 3%, and 0-100% heavy water is able to be determined simply and rapidly with good reproducibility.

Selected ion monitoring assay for the antidepressant maprotiline.

A procedure is described which permits the determination of maprotiline in biological fluids at concentrations ranging from 0.5 to 150 ng ml-1. It relies on the use of N-desmethylclomipramine or isotope labeled maprotiline as the internal standard, on derivatization of the secondary amines with heptafluorobutyric anhydride, and on the combined use of gas chromatography with chemical ionization mass spectrometry and computerized data handling. The assaying procedure is specific, accurate and precise. It is suitable for routine analyses and has sufficient sensitivity to permit monitoring the human blood levels expected from a single therapeutic dose for a week or longer. The method, which can monitor simultaneously isotope labeled and unlabeled maprotiline, can be used to great advantage for reducing variability problems encountered in bioavailability studies.

A sensitive method for the simultaneous determination in biological fluids of imipramine and desipramine or clomipramine and N-desmethylclomipramine by gas chromatography mass spectrometry.

A procedure is described which permits the simultaneous determination of imipramine and desipramine or clomipramine and N-desmethylclomipramine in serum or plasma for concentrations in the range of 1-200 ng ml-1. Detection limits of 0.2 ng ml-1 for imipramine and 0.1 ng ml-1 for desipramine were demonstrated with a signal-to-noise ratio maintained at 2:1 or better. The method relies on the derivatization of the secondary amines with heptafluorobutyric anhydride and is based on the combined use of gas chromatography, electron impact mass spectrometry and computerized data handling. The assaying procedure is specific, accurate and precise. It is suitable for routine analyses and has sufficient sensitivity to permit monitoring the drug and metabolite levels in human plasma or serum resulting from a single therapeutic dose.

Measurement by gas chromatography of urinary hippuric acid and methylhippuric acid as indices of toluene and xylene exposure.

A gas chromatographic method was applied to the determination of the urinary glycine conjugates, hippuric, o-, m- and p-methylhippuric acids. These were extracted with ethyl acetate from urine after acidification with hydrochloric acid. The internal standard solution (heptadecanoic acid methanol solution) was added before extraction and a diazomethane-ether-ethanol solution was subsequently added to the dried extracts. The methylated residues were dissolved in methanol and injected into a gas chromatograph as described by Buchet and Lauwerys (1973). By the combined use of gas chromatography and mass spectrometry the methyl esters of hippuric acid and m-methylhippuric acid were identified in the urine of a volunteer who had been exposed to toluene and m-xylene vapours. When the urine specimen contained salicyluric acid (a urinary metabolite of salicylic acid) two sharp peaks were observed. The faster peak coincided with m- or p-methylhippuric acid. The upper limit of urinary hippuric acid concentration in healthy subjects with no occupational exposure was calculated by this method to be 1.026 microgram/ml (fiducial limit 5%) after correction to 1.024 for variation in urinary density.

Gas-liquid chromatography and mass spectrometry of biologically active primary amines as their isothiocyanate derivatives.

Biologically active primary amines (phenethylamines, amphetamines and tryptamines) form thermally stable isothiocyanate derivatives by reacting with carbon disulfide. Phenolic hydroxyl and indole (NH) nitrogens are further converted to their trimethylsilyl derivatives. The gas chromatographic and mass spectrometric properties of several amines are presented. It is shown that the combined use of gas chromatography and mass spectrometry of these derivatives is well suited for the differentiation of several structural isomers. Fragmentation mechanisms leading to the formation of structurally significant ions are discussed.

An analytical method for polynuclear aromatic compounds in coke oven effluents by combined use of gas chromatography and ultraviolet absorption spectrometry.

An analytical method for polynuclear aromatic compounds in coke oven effluents by combined use of gas chromatography and ultraviolet absorption spectrometry.