Capillary Column Gas Chromatography-mass Spectrometry Research Articles

Characterization of Brazilian oil shale byproducts planned for use as soil conditioners for food and agro-energy production

The Brazilian oil shale byproducts resulting from the Petrosix pyrolysis (retortage) process were submitted to a set of analytical techniques to evaluate their possible use as agricultural soil conditioners. Liquid dichloromethane extracts from the solid samples were analyzed using capillary column gas chromatography–mass spectrometry. The results showed that of the 16 PAHs designated by the U.S. EPA as priority pollutants, only phenanthrene, fluorene and naphthalene, present in the retorted oil shale sample taken from inside storage piles; benzo[k]fluoranthene, present in the dolomite limestone layer between the two layers of oil shale in the mine structure; and naphthalene, present in powdered raw oil shale, were above the limits established by the EPA. The solid Brazilian oil shale byproduct samples were also analyzed by X-ray diffractometry (XRD), diffuse reflectance ultraviolet–visible spectroscopy (DRUV–VIS), X-ray fluorescence spectroscopy (XRF) and electron paramagnetic resonance (EPR) spectroscopy. The XRD analysis showed that the pyrolysis process produces a “weathering” transformation, for example with the appearance of kaolinite diffraction lines in the retorted samples. The DRUV–VIS and XRF spectroscopy results indicated iron oxide goethite interactions with the PAHs present in the solid samples studied. The EPR spectroscopy showed that the samples row oil shale (g=2.0044) and the powder oil shale (g=2.0035), before the dichloromethane extraction, presented organic free radical signals associated with oxygen atoms. The other Brazilian oil shale byproduct samples, before and after the dichloromethane extraction, showed organic free radical signals associated with carbon atoms (g=2.0022–2.0031).

Gas chromatographic–mass spectrometric analysis of dichlorobenzene isomers in human blood with headspace solid-phase microextraction

Headspace solid-phase microextraction (HS-SPME) was utilized for the determination of three dichlorobenzene isomers (DCBs) in human blood. In the headspace at 30°C, DCBs were absorbed for 15 min by a 100-μm polydimethylsiloxane (PDMS) fiber. They were then analyzed by capillary column gas chromatography–mass spectrometry (GC–MS). By setting the initial column oven temperature at 20°C, the three isomers were resolved at the baseline level. p-Xylene-d 10 was used as the internal standard (I.S.). For quantitation, the molecular ion at m/ z 146 for each isomer and the molecular ion at m/ z 116 for I.S. were selected. For day-to-day precision, relative standard deviations in the range 3.2–10.7% were found at blood concentrations of 1.0 and 10 μg/ml. Each compound was detectable at a level of at least 0.02 μg per 1 g of whole blood (by full mass scanning). HS-SPME–GC–MS, when performed at relatively low temperatures, was found to be feasible in toxicological laboratories. Using this method, the plasma levels of one patient who had drunk a pesticide-like material were measured.

Gas chromatographic organic acid profiling analysis of brandies and whiskeys for pattern recognition analysis.

An efficient gas chromatographic profiling and pattern recognition method is described for brandy and whiskey samples according to their organic acid contents. It involves solid-phase extraction of organic acids using Chromosorb P with subsequent conversion to stable tert-butyldimethylsilyl derivatives for the direct analysis by capillary column gas chromatography and gas chromatography-mass spectrometry. A total of 12 organic acids were reproducibly identified in liquor samples (1 mL). When the GC profiles were simplified to their retention index spectra, characteristic patterns were obtained for each liquor sample as well as for each group average. Stepwise discriminant analysis provided star symbols characteristic for each liquor sample and group average. As expected, canonical discriminant analysis correctly classified 23 liquor samples studied into two groups of either brandy or whiskey.

Sulfur-polycyclic aromatic hydrocarbons in tyre pyrolysis oil

Scrap tyres were pyrolysed in two bench-scale reactors: a static batch slow pyrolysis reactor and a fluidized bed reactor. The pyrolysis oils were analysed for their content of sulfur-polycyclic aromatic hydrocarbons (PASH), using a series of liquid column chromatography fractionations with oxidation and reduction to produce a PASH-enriched sample. The PASH were identified and quantified using coupled capillary column gas chromatography-mass spectrometry and capillary column gas chromatography with flame photometric sulfur-selective detection. The PASH identified were mainly dibenzothiophene and methyl, dimethyl and trimethyl dibenzothiophenes, and also naphthothiophenes and their methyl derivatives. The PASH identified were not biologically active according to the literature on the mutagenicity and carcinogenicity of PASH. Increasing temperature of pyrolysis increased the concentration of PASH in the pyrolysis oils; this was attributed to a Diels-Alder type aromatization reaction.

Defective Cholesterol Biosynthesis Associated with the Smith-Lemli-Opitz Syndrome

The Smith-Lemli-Opitz syndrome (frequency, 1:20,000 to 1:40,000) is defined by a constellation of severe birth defects affecting most organ systems. Abnormalities frequently include profound mental retardation, severe failure to thrive, and a high infant-mortality rate. The syndrome has heretofore been diagnosed only from its clinical presentation. Using capillary-column gas chromatography-mass spectrometry, we measured the sterol composition of plasma, erythrocytes, lens, cultured fibroblasts, and feces from five children with the syndrome (three girls and two boys). Plasma cholesterol levels were abnormally low (8 to 101 mg per deciliter [0.20 to 2.60 mmol per liter]) in every patient, being well below the 5th percentile for age- and sex-matched controls. Concentrations of the cholesterol precursor 7-dehydrocholesterol (cholesta-5,7-dien-3 beta-ol), which was not detectable in most of our controls, were elevated (11 to 31 mg per deciliter) more than 2000-fold above normal and were similar to the levels of cholesterol in all tissues from all patients. An isomeric dehydrocholesterol with a structure similar to that of 7-dehydrocholesterol was also detected. The combination of abnormally low plasma cholesterol levels and a high concentration of the cholesterol precursor 7-dehydrocholesterol points to a major block in cholesterol biosynthesis at the step in which the C-7(8) double bond of 7-dehydrocholesterol is reduced, forming cholesterol. The block may be sufficient to deprive an embryo or fetus of cholesterol and prevent normal development, whereas the incorporation of 7-dehydrocholesterol into all membranes may interfere with proper membrane function.

44] Tobacco-specific nitrosamine-hemoglobin adducts

Tobacco-specific nitrosamines are a group of carcinogens formed by nitrosation of nicotine and other tobacco alkaloids. Two of these compounds, N'-nitrosonornicotine (NNN) and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), have been implicated in the etiology of cancers of the oral cavity, lung, pancreas, or esophagus caused by use of tobacco products. Based on the amounts of NNN and NNK in tobacco products, human exposure to these carcinogens is similar to the doses that cause tumors in laboratory animals. NNN and NNK are converted to highly electrophilic intermediates by enzymatic hydroxylation of the carbons α- to the N-nitroso group. Quantitation of hemoglobin adducts of NNN and NNK provide an index of their uptake and metabolic activation. The method consists of four major steps: (1) isolation of hemoglobin and treatment with base to release HPB, (2) solvent partitions to enrich HPB, (3) derivatization of HPB to its pentafluorobenzoate, which can be detected with great sensitivity and selectivity by capillary column gas chromatography–mass spectrometry with negative-ion chemical ionization detection and selected ion monitoring (GC–MS–NICI–SIM), and and (4) quantitation by GC–MS–NICI–SIM.

Polymers with reactive functions as sampling and derivatizing agents—Part 2. Polymeric pentafluorobenzoylating reagent for gas chromatographic–mass spectrometric determination of aliphatic amines

Polystyrene resins containing mixed carbonic–pentafluorobenzoic anhydride functions have been synthesized and utilized for the derivatization of a number of primary and secondary aliphatic amines in high yields, under mild conditions. The pentafluorobenzamides formed were identified and quantified by use of capillary column gas chromatography–mass spectrometry with selected ion monitoring in the negative ion chemical ionization mode. The lower limit of detection for butylamine as a model amine was 2 pg per 2 µl injection and the calibration graph showed linearity in the range 5–250 ng ml–1 with a correlation coefficient of 0.9956. Primary and secondary amines were chosen as substrates for the evaluation and application of the polymeric reagent in view of their good nucleophilicity and their prevalence as pollutants in the workplace.

Determination of mustard gas and related vesicants in rubber and paint by gas chromatography—mass spectrometry

The determination of mustard gas (2,2′-dichlorodiethyl sulphide) and some related vesicants in rubber and paint was investigated. The vesicants were isolated by extraction with methylene chloride or by dynamic headspace analysis at elevated temperatures. The latter procedure had the advantage that high-boiling additives did not interfere during the analysis by capillary column gas chromatography—mass spectrometry. The stability of the vesicants in the materials used proved to be good. No great losses were found after storage for weeks at room temperature.

A gas chromatographic method for the determination of neutral steroid profiles in urine, including studies on the effect of oxytetracycline administration on these profiles in men

A capillary gas chromatographic method for the determination of ‘total’ metabolic profiles of urinary neutral steroids was developed. The method is based on anion exchange Chromatographic separation and purification of monoglucuronide-, monosulphate- and double-conjugated neutral steroids on DEAE-Sephadex A-25 microcolumns and the final analysis of the individual steroids in these conjugate groups is carried out by capillary column gas-liquid chromatography (GC) and gas chromatography-mass spectrometry (GC-MS). The method was shown to provide a convenient and accurate determination of total metabolic profiles of neutral steroids in urine and thus, can be used for metabolic studies of steroids and for diagnostic purposes. In the present investigation the effect of a tetracycline antibiotic on the production and metabolism of neutral steroids in men was studied during a 5-day oral administration of oxytetracycline. The results showed that the influence of oxytetracycline on neutral steroids was minor and mainly restricted to the changes in urinary neutral steroid glucuronide excretion. Oxytetracycline decreased the mean daily excretion of total neutral steroid monoglucuronides by 20% and a statistically significant decrease was found in the urinary excretion of 3α-hydroxy-5β-androstan-17-one-glucuronide (etiocholanolone, 31%, P < 0.05), 5β-pregnan-3α,20α-diolglucuronide (pregnanediol, 32%, P < 0.05) and corticosteroid glucuronides, including 3α,11β,17α,20β,21-pentahydroxy-5β-pregnan- and 3α, 17α,20β,21-tetrahydroxy-5β-pregnan-11-one-glucuronides (β-cortol and β-cortolone, 36%, P < 0.05). The reason for this effect is unknown, but may be partly due to inhibition of intestinal hydrolysis of biliary steroid conjugates, which previously was shown to result in an interruption of enterohepatic circulation of steroids and an increased excretion of steroid conjugates by the faecal route.

Isatin (indole-2,3-dione) in urine and tissues: Detection and determination by gas chromatography—mass spectrometry

A simple procedure based upon capillary column gas chromatography-mass spectrometry (GC—MS) is described for the detection and determination of isatin (indole-2,3-dione) in body fluids and tissues. After addition of 5-methylisatin as internal standard to urine or tissue homogenates, organic extracts are dried and derivatized successively with hydroxylamine hydrochloride and the reagent N- tert.-butyldimethylsilyl-N-methyltrifluoroacetamide (MTBSTFA). The tert.-butyldimethylsilyl derivatives obtained show good GC—MS properties and allow quantification by selected-ion monitoring of m/z 333 (isatin) and m/z 347 (internal standard). Adult and newborn human urine output values lie in the ranges 0.4–3.2 mg/mmol of creatinine (5–30 mg per 24 h) and 0.002–0.518 mg/mmol of creatinine, respectively. There is a discontinuous regional distribution in rat tissues. The GC—MS properties of a number of derivatives formed by successive reaction of isatin with hydroxylamine hydrochloride (or methoxyaminehydrochloride or ethoxyamine hydrochloride) and MTBSTFA, bis(trimethylsilyl)trifluoroacetamide, pentafluoropropionic anhydride or pentafluorobenzyl bromide are also described.

Study of human urinary metabolism of fenfluramine using gas chromatography—mass spectrometry

The metabolism of (±)fenfluramine, 1-( m-trifluoromethylphenyl)-2-N-ethylpropane, an anoretic agent, was investigated in humans. The analysis method was based on the use of ion-exchange resin extraction, solid-phase purification on the Bond Elut™ C 8 cartridge, gradient elution high-performance liquid chromatography, enzymic hydrolysis of conjugates, further purification by Bond Elut C 8 cartridge, derivatisation and capillary column gas chromatography—mass spectrometry (GC—MS). After administration of a 1 mg kg −1 oral dose, four metabolites plus unchanged fenfluramine were recovered in the 0–24 h urine from human volunteers and characterised by GC—MS. In the unconjugated form, fenfluramine, norfenfluramine and m-trifluoromethylhippuric acid were detected by GC—MS. In the aglycone form, the major metabolite, 1-( m-trifluoromethylphenyl)-1,2-propane diol (fenfluramine diol), was monitored using GC—MS. The mass spectral characteristics of the m-trifluoromethylhippuric acid methyl ester, 1-( m-trifluoromethylphenyl)-1,2-propane ditrifluoroacetate derivatives and the norfenfluramine and fenfluramine free base obtained under electron-impact ionization are presented. The metabolism of fenfluramine is discussed including a metabolic pathway in man accounting for the formation of its biotransformation products.

Packed column gas chromatography—capillary column gas chromatography—mass spectrometry coupling for the qualitative characterization of technical products

Packed column—capillary column—mass spectrometry coupling was found to be a valuable technique for the enrichment and identification of trace components in products of the chemical industry. Results are presented that were obtained by applying a SiChromat 2 gas chromatograph in the total transfer mode coupled with a Hewlett-Packard MSD 5970 B mass-selective detector for the investigation of some technical products (methanol, caprolactam, dimethylformamide).

Capillary column gas chromatography—mass spectrometry and gas chromatography—tandem mass spectrometry detection of chemical warfare agents in a complex airborne matrix

The chemical warfare agents sarin, soman and mustard were detected and confirmed during full-scanning gas chromatography (GC)—mass spectrometry (MS) at the nanogram level in spiked extracts of a diesel exhaust environment sampled onto the charcoal of a Canadian C2 respirator canister. This matrix, typical of what might be expected under battlefield conditions, was used for the development of a GCMSMS method for the verification of trace levels of sarin, soman and mustard. Chemical interferences associated with this complex sample were virtually eliminated and low-picogram GCMSMS detection limits were estimated for these chemical warfare agents in the presence of numerous interfering diesel exhaust and charcoal bed components.

Identification of mustard related compounds in aqueous samples by gas chromatography/mass spectrometry

Abstract : Thiodiglycol and a number of other compounds were detected during gas chromatographic analysis of aqueous samples obtained from near the site of the former DRES mustard hydrolysate vaults. Hexane extracts of the aqueous samples were analysed by capillary column gas chromatography-mass spectrometry (GC-MS) under both electron impact and chemical ionization conditions. Interpretation of the MS and complementary capillary column GC-fourier transform infrared data led to the characterization and identification of many compounds, including ether/ thioether macrocycles and vinyl alcohol compounds, not previously associated with mustard decomposition. Keywords: Gas chromatography, Mass spectrometry, Chemical ionization, Ammonia, Isobutane, Chemical agent detection, Military chemical agents, Mustard, Canada.

Identification of tabun impurities by combined capillary column gas chromatography—mass spectrometry

A munitions-grade tabun sample containing a number of sample components was studied by combined capillary column gas chromatography—mass spectrometry

Capillary column gas chromatography-mass spectrometry for the determination of the fatty acid composition of human adipose tissue

A procedure for determining the fatty acid composition of human adipose tissue using gas chromatography-mass spectrometry was developed. Adipose tissue was obtained from the lateral upper aspect of the right thigh by needle biopsy and prepared for analysis by lyophilisation, total lipid extraction and base-catalysed transesterification of the complexed fatty acids to form fatty acid methyl esters. Capillary column gas chromatography resolved thirty different peaks, ranging in carbon length from 12 to 24. Provisional identification of the peaks was by cochromatography with authentic standards and confirmed by gas chromatography-mass spectrometry using electron-impact ionisation. Fatty acid methyl esters were quantified in absolute amounts with respect to dry tissue weight and as a percentage of the total fat. Statistical analysis of the results from twenty healthy subjects using the two-tailed unpaired Student's t-test demonstrated women had significantly higher levels of myristoleic and palmitoleic acids ( p<0.001) and lower levels of palmitic acid ( p<0.05) in adipose tissue when compared with the male group. Similarly total saturated fatty acids was lower ( p<0.05) and total monounsaturated fatty acids was higher in women than in men.

Using Headspace Sampling With Capillary Column GC‐MS to Analyze Trace Volatile Organics in Water and Wastewater

Headspace sampling combined with capillary column gas chromatography–mass spectrometry analysis was evaluated for use in the investigation of priority pollutants in water and wastewater. A 3 mL sample loop and cryogenic trapping at ‐80°C were employed to increase the sensitivity into the nanogram‐per‐litre range, and excellent reproducibility was found in the low microgram‐per‐litre range. Separations were accomplished with a coated 30‐m × 0. 32‐mm fused silica capillary column. Mass spectral data were acquired by selective ion monitoring from 50 to 500 amu. The method was applied to water and wastewater samples with good results.

Pyrolysis of tetralin at 450°C

Tetralin was pyrolyzed at a temperature and pressure regimen similar to the petroleum refining process known as delayed coking. Conditions employed were: temperature 450°C, pressure 600 kPa and reaction times of 60 to 300 min. The product composition was analyzed by combined capillary column gas chromatography-mass spectrometry. For all reaction time periods, naphthalene was the major product observed. Other significant products included: 1,2-dihydronaphthalene, 1-methylindan, n-butylbenzene and a tetralin-1-methylindan adduct. Minor products included: indene, decalin,toluene, ethylbenzene, styrene and n-propylbenzene. Gas analysis showed hydrogen, methane, ethene and propene as additional reaction products. The mechanisms of both major and minor product formation are described.

Analysis of alkyl nitrites by capillary gas chromatography-mass spectrometry

This paper presents the analysis of the commonly-abused alkyl nitrites by capillary column gas chromatography-mass spectrometry. It includes the procedure for the preparation of the relevant alkyl nitrites which can be used as a source of reference compounds. The retention index data and the eight most intense peaks in the mass spectra of iso-butyl, iso-pentyl(amyl) and some closely-related nitrites are given.

Specific identification of synthetic organic chemicals in river water using liquid—liquid extraction and resin adsorption coupled with electron impact, chemical ionization and accurate mass measurement gas chromatography—mass spectrometry analyses

Capillary column gas chromatography—mass spectrometry, utilizing electron impact, chemical ionization and accurate mass determinations, was applied to the broad spectrum analysis of synthetic organic chemicals (SOCs) in a river located in the North Carolina Piedmont. The river was sampled at three locations several times during a thirteen-month period. The SOCs were isolated by either resin adsorption or direct methylene chloride liquid—liquid extraction. Of the 48 distinct SOCs detected, those found most frequently included atrazine and methyl atraton (triazine herbicides), dimethyl dioxane, 1,2,4-trichlorobenzen, tributylphosphate, triethylphosphate, trimethylindolinone, and tris(chlorpropyl)phosphate. Many of these chemicals are indigenous to industrial and agricultural activities in the Piedmont. Concentrations of the SOCs were in the ng/l to μg/l range. The qualitative and quantitative data were similar for both extraction methods, but the resin method was more tedious and introduced more artifacts.