The determination of impurities in caprolactam by capillary gas chromatography-mass spectrometry

A capillary gas chromatography-mass spectrometry (GC-MS) technique has been developed for the determination of impurities in caprolactam. The residual solution of the crude product extracted by benzene was analyzed. A total of 28 compounds in the residual solution were separated. In comparison with the mass spectra obtained with those published in data tables, 24 compounds of the 28 were identified. The possible origination of these impurities was discussed and could be significant in the industrial control of caprolactam.     

Screening for diuretics in human urine by gas chromatography-mass spectrometry with derivatisation by direct extractive alkylation

A rapid, sensitive and reliable gas chromatographic-mass spectrometric (GC-MS) screening procedure for diuretics in human urine has been developed. The procedure uses derivatisation by extractive methylation directly from the urine. The suitability of a number of phase transfer reagents and solvents were studied for the detection of sixteen diuretics. The results obtained indicate that the screening procedure employing tetrahexylammonium hydrogensulphate at pH 12 with methyl iodide in toluene at room temperature was the most effective. This method gives selectivity and sensitivities down to 0.03-0.1 microgram/ml and provides a substrate suitable for GC-MS confirmation without further manipulation. The application of the method is demonstrated by the screening of urine for bumetanide, ethacrynic acid, acetazolamide, chlorothiazide and hydrochlorothiazide.     

Determination of carboxylic acids and phenols in water by extractive alkylation using pentafluorobenzylation,glass capillary GC and electron capture detection

A method is presented for the simultaneous determination of a wide range of carboxylic acids and phenols in water. Extractive alkylation is used with the tetrabutylammonium ion as counter ion and pentafluorobenzylbromide as alkylating agent. Extracts are analyzed by glass capillary gas chromatography and electron capture detection. Using one ml of water sample, the detection limit lies in the range of 1–10 μg/l. Application has been made to the analysis of steam condensate and domestic sewage effluent.     

Fatty acid composition of human erythrocyte membranes by capillary gas chromatography-mass spectrometry

Capillary gas chromatographic and gas chromatographic--mass spectrometric methods were employed for profiling total fatty acid content of human erythrocyte membranes. The protocol was designed to efficiently separate, identify, and accurately quantify the fatty acid composition in human erythrocyte membranes. Washed erythrocyte "ghosts" were saponified in aqueous methanolic sodium hydroxide solution and methylated with boron trichloride and acid catalysis. Extracted total fatty acid methyl esters (FAMEs) were analyzed using a highly polar cyanopropylsiloxane SP 2560 fused-silica capillary column. Total run time was 55 min, and 45 FAMEs were tentatively identified by relative retention times compared to those of known FAMEs. Confirmation of identities by mass spectral structure elucidation revealed saturated, mono- and polyunsaturated, and branched-chain FAMEs. The presence of four fatty aldehydes was also confirmed as dimethyl acetal derivatives. Identification of cis/trans isomers was based on relative retention times and characteristic profile of the cis/trans FAME standard. Quantification of FAMEs for normal subjects showed some variation in relative amounts, consistent with expectations based on literature reports on total or phospholipid FAMEs from human erythrocytes. Separation of individual components of fatty acid families (n-3), (n-6), and (n-9) is demonstrated. Losses in relative amounts of polyunsaturated fatty acids upon storing samples were also detectable by this rapid method.     

Direct determination of adipic acid in urine by extractive alkylation

Extractive alkylation procedures are shown to be inhibited by low levels of Cl-. The chloride concentration may be reduced by mercury(II) complexation and dilution. The mercury(II) also enhances the reaction yield through some undetermined mechanism. Minor modifications of procedures for standards allow direct determination of adipic acid in urine.     

Measurement of S-methylcysteine and S-methyl-mercapturic acid in human urine by alkyl-chloroformate extractive derivatization and isotope-dilution gas chromatography-mass spectrometry

S‐methylcysteine (SMC) is a minor amino acid naturally excreted in human urine, a protective agent against oxidative stress and a biotransformation product of the fumigant biocide methyl bromide and of nicotine. A metabolic source of SMC is catabolism of the repair catalytic protein MGMT (EC 2.1.1.37), which specifically removes the methyl group from the modified DNA nucleotide O‐6‐methyl‐guanine to revert the normal GC base pairing. To assess the value of SMC and of S‐methylmercapturic acid (SMMA) as candidate biomarkers of proliferative phenomena, a sensitive analytical method by GC‐MS was applied in a pilot study of healthy subjects to assess their urinary elimination and the intra‐ and inter‐individual variability. Extractive alkylation with butylchloroformate‐n‐butanol‐pyridine (Husek technique) was employed for sample derivatization and isotope dilution GC‐MS with S‐[CD₃]‐SMC and ‐SMMA was applied for specific and sensitive detection. To resolve the target analytes from the main coeluting interferents in the derivatized urine extract a medium‐polarity stationary phase was employed. SMMA was not detected in the morning urine of three healthy fertile‐age women followed for one month above the minimum detectable level of approx. 500 µg/L while SMC concentrations were in the 0.02–0.7 µg/mL range (n = 61) with large inter‐day and inter‐individual variations. In a young healthy male urine samples taken throughout a few days yielded concentrations in the same 90–810 µg/L range (n = 11). These preliminary results points at SMC as a candidate biomarker for the study of methylation turnover in several biochemical processes. Copyright © 2010 John Wiley & Sons, Ltd.     

Pyrolysis-capillary gas chromatography-mass spectrometry for the determination of polyvinyl chloride traces in solid environmental samples

A novel method based on pyrolysis-capillary gas chromatography-mass spectrometry (CGC-MS) was developed for the quantitative analysis of polyvinylchloride (PVC) in solid environmental samples like sludge and dust. The samples are extracted and the extract is fractionated by solid-phase extraction (SPE). Possibly interfering biological and frequently occuring synthetic polymers are removed by this clean-up. The final extract is analyzed by pyrolysis-CGC-MS. Selective detection of PVC is performed by using specific markers in the pyrogram. Quantitation is done on naphthalene. Good linearity was obtained in a range from 0.5 to 100 microg applied to the pyrolyser. The limit of quantitation (LOQ) in sludge and dust samples is 10 mg/kg dry mass. A correlation between PVC and phthalates was made for sewage sludge samples.     

Sensitive determination of diazepam and N-desmethyldiazepam in human material using capillary gas chromatography-mass spectrometry

A reliable and sensitive capillary gas chromatographic-mass spectrometric method was developed for the detection and determination of diazepam and its major metabolite, N-desmethyldiazepam, in human material. Medazepam served as the internal standard. Quantitative determination was achieved using mass fragmentography with selected ions of m/z 256 for diazepam and m/z 242 for N-desmethyldiazepam and medazepam. The limit of detection was 1 ng/g and the recoveries were 98.54 +/- 3.95% for diazepam and 98.66 +/- 6.48% for N-desmethyldiazepam. The calibration graph was linear over the concentration range from 1.0 ng/g to 1.0 microgram/g for diazepam and N-desmethyldiazepam. Using this method, trace amounts of diazepam and N-desmethyldiazepam were detected in the tissues of an autopsied individual.     

Quantitative determination of octadecenedioic acid in human skin and transdermal perfusates by gas chromatography-mass spectrometry

A gas chromatographic (GC) method with mass spectrometric (MS) detection is developed and validated for the accurate and precise determination of octadecenedioic acid (C18:1 DIOIC) in human skin samples and transdermal perfusates. C18:1 DIOIC is extracted using methanol. The saturated analogue 1,18-octadecanedioic acid (C18:0 DIOIC) is added as internal standard. Prior to analysis, both compounds are converted to their trimethylsilylated derivatives using N,O-bis(trimethylsilyl)trifluoroacetamide with 15% trimethylchlorosilane. Quantitation is performed in selected ion monitoring mode with a limit of quantitation of 250 ng/mL. Linearity with a correlation coefficient of 0.998 is obtained over a concentration range of 250-2000 ng/mL. Values for within-day accuracy range from 94.5% to 102.4%, and from 97.5% to 105.8% for between-day accuracy. Within- and between-day precision values are better than 5% and 7%, respectively. The recovery values from the various matrices vary from 92.6% to 104.0%. The GC-MS method is employed for the determination of C18:1 DIOIC after application of an emulsion containing the active ingredient onto human skin in vitro. The results demonstrate that the method is suitable for the determination of C18:1 DIOIC in human skin samples and transdermal perfusates.     

Analysis of drug metabolites by gas chromatography-mass spectrometry using glass capillary columns

Summary The routine use of glass-capillary columns in a general applications laboratory for gas chromatography-mass spectrometry is discussed. The instrumentation is described with emphasis on the interface between glass capillary columns and the mass spectrometer. Two examples of the analysis of metabolites demonstrate the successful use of this system.     

Determination of pyrethroid metabolites in human urine by capillary gas chromatography-mass spectrometry

Summary An analytical method for the simultaneous determination of the pyrethroid metabolites cis and trans-3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropane carboxylic acid, cis 3-(2,2-dibromovinyl)-2,2-dimethylcyclopropane carboxylic acid, 3-phenoxybenzoic acid and 4-fluoro-3-phenoxybenzoic acid in human urine samples is described. The urine is subjected to acid-induced hydrolysis followed by exhaustive solvent extraction, covering both conjugated and free acids, followed by a common derivatisation step yielding the corresponding methyl esters. Quantitation was by diastereomeric, capillary gas chromatography-mass spectrometry. It appears that 4-fluoro-3-phenoxybenzoic acid is a characteristic urinary marker for cyfluthrin exposure. The limits of determination are 0.5–1.0 g L^–1 urine depending on the metabolites concerned. The applicability of the method was tested on urine samples from pest control operators exposed occupationally to cypermethrin and cyfluthrin.     

Measurement of imidazoleacetic acid in urine by gas chromatography-mass spectrometry

Imidazoleacetic acid (IAA), a histamine and histidine metabolite, was quantified in human urine by gas chromatography-mass spectrometry (GC-MS). The acid was separated by ion-exchange chromatography, derivatized as the n-butyl ester with boron trifluoride-butanol and the derivative extracted with chloroform. GC-MS analysis was carried out by selected-ion monitoring of ions m/z 81 and m/z 83 corresponding, respectively, to IAA and [15N,15N']IAA used as internal standard. The mean IAA content in urine was about 8.02 nmol/mg of creatinine. The specificity of measurement was rigorously established by GC retention time, peak shape, ion abundance ratios, and recovery experiments. The method is capable of quantifying IAA in 0.05 ml of urine and in amounts as low as 0.20 nmol.     

气相色谱-质谱法快速测定牙膏中的二甘醇

建立了气相色谱-质谱法（GC-MS）快速测定牙膏中的二甘醇的方法。牙膏样品经三氯甲烷提取后,应用气相色谱-质谱联用仪,以选择离子监测（SIM）模式对其中的二甘醇进行分析。二甘醇的线性范围为21.24-1062 mg/L,线性相关系数（r）为0.9995;检出限和定量限分别为2.0、5.0 mg/L;高、中、低3种浓度下的回收率在88.51%-101.6%之间,相对标准偏差（RSD）在1.6%-8.11%之间;仪器对二甘醇的响应在24 h内保持稳定。     

Multiresidue determination of 77 pesticides in textiles by gas chromatography-mass spectrometry

A simple and efficient method for multiple determination of 77 pesticides, including one organonitrogen, eight carbamate, 12 pyrethroid, 26 organochloride, 30 organophosphorous compounds, in textiles is developed. Six representative textiles are chosen as test samples. Extraction using hexane-ethyl acetate (1:1) assisted by ultrasonic processor is carried out twice, followed by clean-up using solid-phase extraction on a florisil column. The final solution is analyzed using gas chromatography-mass spectrometry, and 77 pesticides are determined. This method is highly sensitive, selective, and reproducible, with a broad linear range and reliable accuracy. Six blank samples are spiked with 0.50 and 2.00 mg/kg of the 77 pesticides, and the corresponding recoveries are between 64.5% and 99.1%; the precisions range from 4.04% to 14.78%; and the minimum detection limits of this method are 0.02-0.20 mg/kg.     

Quantitative determination of tramadol in human serum by gas chromatography-mass spectrometry

A gas chromatographic-mass spectrometric method for the quantitative determination of tramadol in human serum, plasma or whole blood samples is described. The method involves the use of [2H2, 15N]tramadol hydrochloride as an internal standard and chemical ionization with isobutane, employing single-ion monitoring for quantification. It is specific, sensitive and precise, and has high accuracy. The within-run coefficient of variation is about 1% between 25 and 200 ng/ml and 1.8-2.9% at the lowest concentrations tested (6.25 and 12.5 ng/ml). The between-run coefficient of variation increases from 1.6% to 5.2% with decreasing concentration from 200 to 12.5 ng/ml. The calibration graphs were linear in the tested concentration range, and the accuracy of the assay was not dependent on the sample volume used. The detection limit was about 4 ng/ml for serum samples of 1 ml. The method proved suitable for pharmacokinetic studies. Its high sensitivity allows measurements of serum concentrations for at least 30 h after the single administration of therapeutic doses of tramadol hydrochloride.