Identification of low chlorinated biphenyls in human milk by gas chromatography--mass spectrometry.

Trichlorobiphenyl and tetrachlorobiphenyls in human milk were analysed by gas chromatography--mass spectrometry and mass fragmentography using silicone OV-1 and Apiezon L grease as stationary phases. Low-chlorinated biphenyls had been considered to be excreted rapidly from the body, but in this work quantities of tri- and tetrachlorobiphenyls amounting to approximately 30% of the total of polychlorinated biphenyls (PCBs) accumulated in the milk were identified. This result is important in relation to the quantification of PCBs and in studies of the mechanism of biological degradation.     

Microdetermination of caffeine in blood by gas chromatography--mass spectrometry

A micromethod for the quantitative analysis of caffeine present in small quantities (100 microliter) of whole blood is described. It is based on the gas chromatographic--mass spectrometric analysis of chloroform extracts of biological samples. The method is relatively simple, rapid, specific and sensitive; as little as 20 ng of caffeine can be measured.     

Quantitation of a metal deactivator additive by derivatization and gas chromatography--mass spectrometry

The quantitative analysis of phenolic and amine-containing petroleum additives can be challenging. One such compound-N,N'-disalicylidene-1,2-propanediamine, a common metal deactivator additive (MDA)--is thought to inhibit fuel oxidation catalyzed by metals both in the fuel and on surfaces. The ability to measure the concentration of MDA in storage stability tests, thermal-stressing studies, and field samples is important. Quantitating low concentrations of MDA can be difficult because of surface adsorptivity due to the phenol and amine functional groups. This paper describes the shortcomings of direct-injection gas chromatography-mass spectrometry to quantitate MDA as well as a solution to the analytical problem using the common silylation agent BSA to derivatize the MDA. Results demonstrate that the silylation technique is suitable for the determination of MDA concentrations in aviation fuel samples and suggests that the MDA may be readily determined in other petroleum products with a lower detection limit for MDA of 0.5 mg/L. Measurements conducted in heated batch reactors indicate that MDA concentration is reduced as hydrocarbon fuels are stressed. In addition, only free or available MDA is measured by this technique, not MDA that is complexed with metals.     

Analysis and kinetics of 2,4-dinitrophenol in tissues by capillary gas chromatography--mass spectrometry

Five groups of six ICR mice were orally dosed with 22.5 mg/kg 2,4-dinitrophenol. Groups were sacrificed at 1, 3, 6, 12, and 24 h post treatment, and serum, liver, and kidney tissues were collected for analysis of dinitrophenol content. Quantitation was performed via a capillary gas chromatography--mass spectrometry technique after liquid--liquid extraction of biological specimens spiked with a trideuterated dinitrophenol internal standard. Concentration versus time data for each tissue were subjected to pharmacokinetic analysis. Similar two-compartment open models were found to characterize most phases of the disposition of this compound. The kidney appears to maintain a more persistent low concentration of 2,4-dinitrophenol.     

Quantification of a number of biogenic amines and their metabolites in brain homogenates by gas chromatography--mass spectrometry

A sensitive method is described for the assay of various biogenic amines and their metabolites from brain tissue homogenates. Based on gas chromatography-mass spectrometry and selected ion monitoring, the method allows reliable low-level quantification of the compounds of interest. By careful study of reaction conditions both in the preparation of derivatives for gas chromatography and in the synthesis of deuterated analogues for internal standard use, relatively simple procedures could be applied with good analytical efficiency. Correlation of the results with those obtained by a high-performance liquid chromatographic procedure was also investigated, and a neurologic application of the method is briefly discussed.     

Identification of radiolytic products from N-nitrosodimethylamine and N-nitrosopyrrolidine by gas chromatography and mass spectrometry

The radiolytic products of N-nitrosodimethylamine (NDMA) and N-nitrosopyrrolidine (NPYR) dissolved in dichloromethane (DCM) were identified after gamma irradiation. The UV spectra of NDMA and NPYR indicated that irradiation reduced the typical peak of NDMA at 258 nm and NPYR at 260 nm.The major radiolytic components identified in irradiated NDMA were ethyl acetate and 2-dimethyl propanol. The irradiated NPYR dissolved in DCM and produced 2-butanone and 2-methyl-6-propyl piperidine as the major radiolytic components. 2-Methyl-6-propyl piperidine was the component detected in the greatest concentration in irradiated NPYR.     

Analysis of methyl tert.-butyl ether and its degradation products by direct aqueous injection onto gas chromatography with mass spectrometry or flame ionization detection systems.

A method was developed to analyze methyl tert.-butyl ether (MTBE) and its degradation products by gas chromatography with mass spectrometry (GC-MS) or flame ionization detection (FID) with direct aqueous injection. The column had dimensions of 30 m x 0.25 mm with film thickness 0.25 microm and a stationary phase of FFAP (nitroterephthalic acid-modified polyethylene glycol). The optimized GC conditions for non-acid components were as follows: carrier gas flow-rate,l mL/min; oven temperature, 35 degrees C for 5.5 min, ramped to 90 degrees C at 25 degrees C/min, then ramped to 200 degrees C at 40 degrees C/min and held at 200 degrees C for 8 min. The conditions for the acid components were: carrier gas flow-rate, 1 mL/min; oven temperature, 110 degrees C for 2 min, ramped to 150 degrees C at 10 degrees C/min, then ramped to 200 degrees C at 40 degrees C/min. The injection port contained a silanized-glass reverse-cup liner filled with Carbofrit. The minimum concentrations for the linear range for the selective ion monitoring mode were 30 to 100 microg/L, depending on the analytes. The minimum detection limit was 1 mg/L for MTBE and tert.-butanol when using FID. More components could be analyzed with the FFAP-type column than with the cyanopropylphenyl-dimethyl polysiloxane-type column.     

Identification of the chlorination products of aliphatic ketones by gas chromatography and gas chromatography/mass spectrometry

The differences in the gas chromatographic retention indices of the chlorination products of aliphatic ketones and parent carbonyl compounds (ΔRI) are constant, and their numeric values depend on the number and position of chlorine atoms in the molecule. A simplest version of an additive scheme for the evaluation of retention indexes is developed to identify the chloro derivatives of carbonyl compounds. The order of the chromatographic elution of diastereomeric α,α′-dichloro-k-alkanones (k > 2) is found.     

Identification of degradation products of 2-chloroethyl ethyl sulfide by gas chromatography-mass spectrometry

Gas chromatography-mass spectrometry under both electron impact and methane chemical ionization conditions has been used to detect impurities and degradation products present in the mustard simulant 2-chloroethyl ethyl sulfide, with a detection limit of 0.05 area percent. After one and two years of storage at ambient temperatures, the primary degradation product was 1,4-dithiane formed from the degradation of dimeric sulfonium ions. Oxidation and hydrolysis products were not detected.     

气相色谱-串联质谱法测定食用油中两种非邻苯二甲酸酯类增塑剂

建立了气相色谱-串联质谱同时测定食用油中对苯二甲酸二（2-乙基己基）酯和偏苯三甲酸三（2-乙基己基）酯两种非邻苯二甲酸酯类增塑剂的方法。样品采用乙腈提取,于-20℃冷冻除脂净化,用气相色谱-串联质谱选择反应监测模式测定。两种化合物的检出限为0.03 mg/kg,定量限为0.1 mg/kg,线性范围为0.1~10 mg/kg。3个添加水平（0.1、0.3和1.0 mg/kg）下的回收率为81.04%~108.31%,相对标准偏差为0.70%~9.91%。该方法简便、准确,适用于食用油中对苯二甲酸二（2-乙基己基）酯和偏苯三甲酸三（2-乙基己基）酯的检测。     

Quantitation of formate by solid-phase microextraction and gas chromatography--mass spectrometry utilizing a [13C]formate internal standard

A new method for the analysis of formic acid was developed using gas chromatography-electron impact ionization mass spectrometry in the selected ion monitoring mode and solid-phase microextraction. Using this method with [13C]formic acid as an internal standard, the peak area ratio of [12C]formic acid/[13C]formic acid was not affected by differing methanol or sulfuric acid concentrations during the esterification and fiber adsorbing step. In comparison, the peak area ratio of formic acid/acetonitrile as detected by conventional GC with flame ionization detection was greatly affected by methanol or sulfuric acid concentrations. The formic acid calibration curve of our method showed excellent linearity over the range 5 to 200 microM. The within- and between-run assay relative standard deviations for the formic acid concentration were all less than 1.70%.     

Identification of 2,3-butanedione monoxime hydrogenation products by gas chromatography-mass spectrometry in an ion trap mass spectrometer.

The reduced products of 2,3-butanedinone monoxime by reaction with hydrogen in the presence of homogeneous catalysts were identified by gas chromatography coupled to an ion trap mass spectrometer operating either in the electron impact or chemical ionization mode. The major hydrogenation products were found to be several heterocyclic nitrogen-containing compounds: tetramethylpyrazine, 2,4-dimethyl-3-ethylpyrrole, 3,4,5-trimethylpyrazole, 2,5-dimethyl-1-propylpyrrole, 3-acetyl-2,4-dimethylpyrrole, 3,5-dimethyl-4-allypyrazole and tetramethylpyrazine N-monoxide.     

固相萃取-气相色谱法测定合成气制烯烃产物中的含氧化合物

采用C18固相萃取技术对合成气制烯烃(SGTO)的产物进行预处理,将产物分离为含氧化合物与烃类,采用气相色谱-质谱法(GC-MS)考察分离效果并鉴定产物中的含氧化合物,使用氢焰离子化检测(FID)定量实际样品中的含氧化合物,使用其正构2-酮、正构醇的响应因子作为同碳数酮、醇的FID响应因子。优化C18小柱洗脱条件,使用标准样品比较预处理前后的方法回收率。醇类标准品回收率为88%~98%,酮类标准品回收率为64%~87%。在197~4785 mg/L范围内,标准品具有较好的线性关系,相关系数均大于0.99。定性并定量测定了SGTO产物中的67种含氧化合物,发现正构醇、正构2-酮为SGTO产物中的主要含氧化合物,同时存在少量其他异构体。该方法操作简单、快速、样品需求量小,并能够在10 min内完成样品的预处理。分析结果为SGTO工艺催化剂、动力学深入研究提供了必要的基础数据。     

Identification of diterpenes in canvas painting varnishes by gas chromatography-mass spectrometry with combined derivatisation

A derivatisation method that combines the formation of ethyl esters from the carboxylic groups and trimethylsilyl ethers from hydroxyl groups of the components of diterpenic resins is presented in this paper. This methodology involves two experimental steps: (1) formation of ethyl esters using ethyl chloroformate; and (2) the esterified compounds are lead to react with trimethylsilylimidazole to form the corresponding trimethylsilyl ethers. The main advantage of the proposed method is the possibility of performing simultaneously the analysis of amino acids from proteins, fatty acids from drying oils, and diterpenic compounds from natural resins usually found in works of art. This methodology is of considerable interest due to the requirements of minimum sampling that usually involves the analysis of works of art. A chemometric study has been developed to adjust the optimal working conditions of the proposed derivatisation method in which chromatographic peak areas of the larixyl acetate derivative and the abietic acid derivative referred to n-hexadecane as internal standard have been compared. Samples of Venetian turpentine naturally aged have been used in this study. Finally, the efficiency of the proposed derivatisation method has been tested on other diterpenic resins and pigments commonly used in fine arts such as Strasbourg turpentine, Canada balsam, colophony, copper resinate and a sample from a Renaissance Altarpiece.     

Identification of 19 phthalic acid esters in dairy products by gas chromatography with mass spectrometry

A detection method for 19 kinds of phthalic acid ester compounds analyzed by n‐hexane/ether/acetonitrile 1:7:8 v/v/v mixed solvent extraction, quick, easy, cheap, effective, rugged, and safe purification and internal standard method of quantitative gas chromatography with mass spectrometry was established. This method can effectively remove interfering materials, such as lipids, fatty acids, and pigments, from dairy products. The 19 kinds of phthalic acid ester compounds were within a 0.025–0.2 mg/kg range, the recovery rate was 65.2–125.7%, relative standard deviation was 7.9–15.4% (n = 6), and the limit of detection was 0.005–0.02 mg/kg. Concentrations of the 19 kinds of phthalic acid ester compounds ranged between 0.01 and 0.12 mg/kg in ten dairy materials and 20 dairy products. The established method is simple, rapid, accurate, and highly sensitive.     

Identification of a tolfenamic acid metabolite in the horse by gas chromatography-mass spectrometry.

A tolfenamic acid metabolite, a hydroxylated product, has been identified in equine plasma and urine samples using gas chromatography-mass spectrometry in the electron-impact and chemical-ionization modes. The method also allows the qualitative monitoring of the elimination of the drug and its metabolites from plasma. The two compounds are detected up to 48 and 24 h, respectively, after a single oral administration of a 30 mg/kg dose. The simultaneous detection of the two products increases the reliability of anti-doping control analysis.