Pulsed-valve chemical ionization for gas chromatography/fourier-transform mass spectrometry

The pressure requirements for chemical ionization g.c./F.t.m.s. which restrict mass resolution and accuracy are overcome through use of a pulsed valve that provides momentary reagent gas pressures. For alternate electron impact (EI)/chemical ionization (c.i.) g.c./F.t.m.s., similar resolution for both e.i. and c.i. data is demonstrated. The efficiency of chemical ionization with the pulsed valve is similar to static high pressure c.i. measurements of several model compounds. Results from the analysis of peppermint oil and a fuel additive illustrate the potential information available from a single g.c./F.t.m.s. experiment.     

Data evaluation in combined gas chromatography—infrared spectroscopy—mass spectrometry

The technique of gas chromatography—infrared spectroscopy—mass spectrometry (g.c./i.r./m.s.) has great potential m qualitative and quantitative analysis. The utility of g.c./i.r./m.s. is presently limited by the lack of methods for reduction of the large amounts of data produced from complex mixtures. Approaches to qualitative and quantitative data evaluation which take into account differences in instrumental configuration are presented.     

Limitations of some esterification techniques in structural studies of kerogen-derived acids

Oxidative degradation techniques for characterizing kerogens in oil shales often lead to major yields of precipitated acids (PA), which are less amenable than soluble acid products to analysis by gas chromatography/mass spectrometry (g.c./m.s.). A PA complex produced by oxidation of a Julia Creek (Queensland) kerogen was studied by applying four different esterification techniques before g.c./m.s. Methods based on reaction with diazomethane or boron trifluoride/methanol were of limited effectiveness. Reaction with dimethyl sulphate in acetone with potassium carbonate catalyst led to the detection of by far the widest range of components in the PA complex. This method is recommended for esterifying acid products derived from kerogen, especially in comparative characterization studies of kerogens.     

Automated accurate mass data processing using a gas chromatograph/time-of-flight mass spectrometer in drug discovery

A gas chromatograph/time-of-flight (GCT) mass spectrometer, with high mass measurement accuracy to within 5 ppm, has been used for the automated accurate mass analysis of multicomponent mixtures and drug discovery compounds. A multicomponent mixture was analyzed several times over the course of a week to assess the reproducibility and ruggedness of the automated method while operating the GCT in electron ionization mode. For example, the data for 31 radical cations generated via electron ionization was processed using automated software (i.e. OpenLynx) to provide for mass accuracies less than 5 ppm for nearly 100% of the ions from multiple injection data. Mass accuracies of the radical anions of polyaromatic hydrocarbons generated via negative chemical ionization, and protonated pyridines and quinolines generated via methane chemical ionization, were mainly less than 5 ppm from multiple injection data. In addition, the automated method has been used for the accurate mass analysis of drug discovery compounds.     

A totally automated data acquisition/reduction system for routine treatment of mass spectroscopic data by factor analysis

Target transformation factor analysis is applied to typical data from gas chromatography—mass spectrometry and solid-probe mass spectrometry to determine rapidly the number of components in unresolved or partially resolved peaks. This technique allows the detection of hidden impurities which often make interpretation or quantification impossible. The error theory of Malinowski is used to assess the reliability of the results. The totally automated system uses a commercially available g.c.—m.s. data system interfaced to a large computer, and the number of components under a peak can be determined routinely and rapidly.     

Selective detector of 1,2-propylene glycol dinitrate, 1, propylene glycol mononitrate,and 2-propylene glycol mononitrate using gas chromatography/ thermal energy analyzer or liquid chromatography/ electrochemical detection

Mono- and di-nitrated propylene glycols can be separated and detected using either a gas chromatogph equipped with a nitro-specific thermal energy analyzer (g.c./t.e.a.) or a high-performance liquid chromatograph equipped with an electrochemical detector in the reductive mode (l.c./e.c.). The g.c./t.e.a. exhibits a linear range of three orders of magnitude and provides detection limits in the μg ml^?1 range or lower for these three compounds. The l.c./e.c. provides a linear response over two orders of magnitude and is best suited for the determination of propylene glycol dinitrate. Trapping of these glycols on Amberlite XAD-2 resin is discussed.     

Flow injection gas chromatography with sulfur chemiluminescence detection for the analysis of total sulfur in complex hydrocarbon matrixes

A fast and reliable analytical technique for the determination of total sulfur levels in complex hydrocarbon matrices is introduced. The method employed flow injection technique using a gas chromatograph as a sample introduction device and a gas phase dual‐plasma sulfur chemiluminescence detector for sulfur quantification. Using the technique described, total sulfur measurement in challenging hydrocarbon matrices can be achieved in less than 10 s with sample‐to‐sample time <2 min. The high degree of selectivity and sensitivity toward sulfur compounds of the detector offers the ability to measure low sulfur levels with a detection limit in the range of 20 ppb w/w S. The equimolar response characteristic of the detector allows the quantitation of unknown sulfur compounds and simplifies the calibration process. Response is linear over a concentration range of five orders of magnitude, with a high degree of repeatability. The detector's lack of response to hydrocarbons enables direct analysis without the need for time‐consuming sample preparation and chromatographic separation processes. This flow injection‐based sulfur chemiluminescence detection technique is ideal for fast analysis or trace sulfur analysis.     

Method validation for the determination of propellant components by Soxhlet extraction and gas chromatography/mass spectrometry

A fast, sensitive, and accurate GC/MS method for the quantification of aliphatic nitroesters (ethylene glycol dinitrate, nitroglycerin, and triethylene glycol dinitrate) and aromatic amines (diphenylamine, 2-nitrodiphenylamine, and triphenylamine) in propellants was developed and validated. This method comprises a Soxhlet extraction step with dichloromethane, followed by separation on a capillary column MDN-5. Ionization of the analytes is carried out using electron ionization. The limit of quantification of the method was 1% w/w for aliphatic nitroesters and 0.1% w/w for aromatic amines (diphenylamine and triphenylamine). Values of repeatability and reproducibility for analyzed compounds were smaller than values of the maximum allowed tolerances of the Horwitz-equation RSD(max) and 2/3 RSD(max). Values of accuracy for selected compounds were below the acceptable threshold of 15% for all tested levels in the range of calibration curve excepting the lowest concentration of calibration curve for nitroglycerin and aromatic amines. During the validation of method, temperature instability in injection port of gas chromatograph and column was observed for 2-nitrodiphenylamine. Hence, it follows worse results of accuracy and linearity and 2-nitrodiphenylamine was not validated successfully.     

Identification and determination of metabolites in plant cell biotechnology by gas chromatography and gas chromatography/mass spectrometry : Application to Nonpolar Products of Chrysanthemum cinerariaefolium and Tagetes Species

Gas-liquid chromatography (g.l.c.) and gas-liquid chromatography/mass spectrometry (g.c./m.s.) were used for profile analysis and for identification, confirmation and determination of traces of nonpolar metabolites synthesized in plant tissue, calli and in suspension-cultured cells of Chrysanthemum cinerariaefolium (pyrethrum) or Tagetes species (marigold). When dried leaf samples (1–20 mg) were tested, six pyrethrins were detected simultaneously at the picogram level with an electron capture detector. This method permits the early selection of high yielding tissues and calli for the development of plant cell cultures. α-Terthienyl was quantified at the nanogram level with the electron capture detector; calibration graphs were linear between 0.2 and 20 ng and the minimum detectable quantity was about 0.1 ng. The concentration of α-terthienyl in air-dried roots of T. erecta was 140 μg g^?1. However, this procedure used alone is not reliable, because α-terthienyl and the pyrethrin Cinerin I have the same retention time. Mass spectrometry is needed for identification and confirmation. Profile analysis of a leaf extract of T. minuta by high-resolution g.c./m.s, and accurate mass measurements showed 13 nonpolar compounds, of which 9 were tentatively identified; they include 2 sesquiterpenoids, 3 thiophenes, 2 sterols with a precursor and ethyl linolenate. Analyses of T. minuta indicated that in calli and cell suspensions, plant sterols are synthesized but sesquiterpenoids or thiophenes are not produced.     

The mass spectra of TMS-ethers of deuterated polyalcohols. A contribution to the structural investigation of sugars

Aldoses, ketoses, deoxy-aldoses, deoxy-keto-aldoses, lactones, deoxy-lactones and other similar compounds are readily reduced by NaBD₄ to the corresponding polyalcohol. Their trimethylsilyl ethers show characteristic mass spectra which allow firm assignments of the position of deuteration and hence of the nature of the starting sugar compound. The g.c./m.s. coupling technique even allows trace analysis since full information can be derived from the most intense fragments of the mass spectra.     

GC-MS/FID测定环境空气中57种臭氧前体物

建立了GC-MS/FID测定环境空气中57种臭氧前体物的分析方法.优化三级冷阱捕集温度、三级冷阱解析温度、初始柱温、毛细管色谱柱等实验条件.优化条件为:采用硅烷化的苏玛罐采集环境空气,目标组分经三级冷阱在-180℃低温浓缩富集,80℃解析,初始柱温为15℃,结合中心切割技术,将乙烷、乙烯、乙炔、丙烷、丙烯切割至TG-B...     

A liquid chromatography tandem mass spectrometry method for simultaneous analysis of 46 atmospheric particulate-phase persistent organic pollutants and comparison with gas chromatography/mass spectrometry

A novel multi-analyte method for the simultaneous determination of 46 compounds of environmental concern, most of them belonging to the category of persistent organic pollutants, was developed using high-performance liquid chromatography and the results were compared to those obtained by gas chromatography. This study was performed in perspective of a cumulative exposure assessment of substances of health concern in environments where high levels, relatively to airborne particulate matter, can be found. The target compounds included polychlorinated biphenyls, brominated flame–retardants and derivatives of polycyclic aromatic hydrocarbons.

The multi-analyte method was evaluated in air particulate matter in terms of reproducibility, linearity, recovery, limits of detection and quantification and matrix effect. The recovery was above 70% for all the analytes, whereas limits of quantification ranged between 23 and 390 pg?m^?3 in liquid chromatography and less than ten times in gas chromatography–mass spectrometry.

Matrix effect was generally negligible for both the techniques, except the case of the detection of oxygenated derivatives of polycyclic aromatic hydrocarbons by gas chromatography.

In order to demonstrate the efficacy and to assess the method performances (accuracy and precision), both the techniques were applied to standard reference materials, and the results were compared, discussing their advantages and disadvantages.

The method was finally applied to a real sample of indoor airborne particulate matter with aerodynamic diameter ≤4 μm (PM₄).

We demonstrated that liquid chromatography was the only technique able to analyse the 46 compounds, including thermally degradable ones, with a single chromatographic run without derivatisation steps. On the other hand, gas chromatography still presents higher sensitivity for the detection of some of the investigated compounds. This study can be considered only explorative and further improvements can be expected with new-generation LC-MS instruments (10–100 times more sensitive).     

Prediction,optimization of separation,and identification of unknown compounds in capillary gas chromatography

A procedure for the identification and separation of unknown compounds by capillary gas chromatography is described. The procedure involves a live retention time database and optimization of the separation. After initial chromatography of the sample, a rough search lists all the possible compounds it might contain and the analyst then uses his experience to discard those compounds in the list which are unlikely to be present. The multi-component separation is then optimized over the whole range of defined starting temperatures and programming rates, in order to produce the best possible separation of the sample components, and the chromatography repeated using the results obtained from the optimization procedure. Further search operations within a given search window will then report the compound names, and related information, for each peak. Since the identification operation is performed at least twice during the procedure, and the optimization of the separation assists the identification by separating possibly overlapped peaks, the confidence of the qualitative analysis is higher than may be obtained using standards alone. If the reproducibility of isothermal indices measured on columns could be guaranteed, this procedure could be used instead of performing chromatography on standards of the compounds contained in the database, regardless of changes in column dimensions, phase ratio, and operating conditions in temperature programmed analysis.     

顶空气相色谱法测定化妆品中15种挥发性有机溶剂残留

建立了化妆品中15种挥发性有机溶剂残留的顶空气相色谱测定方法。样品经60 ℃、30 min静态顶空后,采用气相色谱-氢火焰离子化检测器进行检测,外标法定量。加标回收试验结果表明: 15种挥发性有机溶剂残留平均回收率为62.8%～116%,相对标准偏差均小于5%。方法的检出限为0.09～0.68 mg/kg。该方法可有效克服基体干扰,一次进样可同时分离和测定化妆品中15种挥发性有机溶剂,准确灵敏,简单快速,适用于化妆品中挥发性有机溶剂残留的检测。     

超临界CO2流体萃取法与水蒸气蒸馏法提取荆芥穗挥发油化学成分的研究

采用超临界CO2萃取法(SFE)与水蒸气蒸馏法(SD)从荆芥穗中提取挥发油。采用SE-54毛细管柱进行分析,用气相色谱-质谱法对挥发油中各种化学成分进行鉴定,用归一化法测定各组分的含量。色谱条件:SE-54毛细管柱 (30 m×0.25 mm i.d.,0.25 μm),柱温50 ℃(3 min)5 ℃/min180 ℃(2 min)10 ℃/min260 ℃(50 min);分流进样,分流比1∶50;进样口温度280 ℃。在采用超临界CO2萃取法提取的挥发油中共鉴定出54种成分,其主要成分为长叶薄荷酮、薄荷酮、亚油酸氯化物等;在水蒸气蒸馏法提取的挥发油中共鉴定出39种成分,其主要成分为长叶薄荷酮、薄荷酮、柠檬烯等。超临界法较水蒸气法更加稳定可靠,重现性好,适用于中药挥发油的化学成分分析。     

Analysis of alkylbenzene samples by comprehensive capillary liquid chromatography x capillary gas chromatography

The constituents in synthetic alkylbenzene samples were analyzed by a comprehensive capillary liquid chromatography (micro-LC) x capillary gas chromatography (CGC). The micro-LC separates the mixture into aliphatic compounds, monosubstituted alkylbenzenes, multisubstituted alkylbenzenes and binuclear aromatic compounds. Each fraction from a single micro-LC injection is stored in turn in a multiloop interface, and then transferred online into CGC sequentially with large volume in-column splitless injection technique for detailed analysis. No sample discrimination was found with this coupling and injection technique. Both the micro-LC column dimension and transfer speed of fraction from interface to CGC were optimized. Quantitative results and the carbon number distribution of each chemical class are obtained by using the comprehensive micro-LC x CGC with flame ionization detection. The reproducibility of peak area is better than 2% RSD.     

固相萃取采样和气相色谱-质谱检测液化石油气中的芳烃杂质（英文）

建立石墨化碳(GCB)为吸附剂的动态采样系统,可实现液化石油气(LPG)中芳烃杂质的采样和同步萃取富集。LPG中的芳烃杂质(苯、甲苯、二甲苯、苯乙烯和萘)被快速捕集后,进行气相色谱-质谱(GC-MS)定性定量分析。与C18和苯乙烯二乙烯苯吸附剂(PS-DVB)相比,GCB填充柱对芳烃杂质的萃取效率最高。评价了基于GCB填充柱采样的吸附效率、重现性和贮存稳定性。采样和分析方法对氮气模拟气流中8种芳烃的定量分析线性范围为15~1 000μg/m~3。所开发的方法具有回收率高(92.9%~109.0%)、检出限低(1.0~6.2μg/m~3)、准确性好(相对标准偏差为0.6%~5.8%)和准确度高(标准偏差为0.8%~8.2%)等优点。     

Evidence for selectivity of absorption of volatile organic compounds by a polydimethylsiloxane solid-phase microextraction fibre

Solid-phase microextraction using a 30 microns polydimethylsiloxane fibre has been used to sample the volatile organic compounds from standard mixtures and from mixtures produced by the decomposition of organic compounds. This method of sampling has been compared with the direct injection of an aliquot of headspace gas and shows an enrichment factor of approximately 100 over a 1 ml gas injection for organosulphur gases such as dimethyldisulphide. The performance of the fibre has been evaluated with respect to accuracy and precision at several concentrations in representing the composition of multicomponent mixtures. It was found that the presence of a second component in a gas sample reduced the capacity of the fibre to absorb the primary component. The selectivity of the fibre for various volatile compounds with differing functionality was also studied. It was found that the non-polar polydimethylsiloxane fibre preferentially absorbed the non-polar components of a mixture, e.g. nonane and, correspondingly, under reported the more polar components, e.g. ethanol. Hence, the fibre discriminates in favour of non-polar and against polar components in a mixture in comparison with direct analysis of a headspace sample. Thus, quantitation of a component in a multi-component mixture is liable to error from competitive interference from other components. A major advantage of the technique, however, is that it does not absorb, and therefore introduce, water into the analytical system.     

Development and evaluation of a calibration gas generator for the analysis of volatile organic compounds in air based on the injection method

The development and operational evaluation of a calibration gas generator for the analysis of volatile or ganic compounds (VOC) in air is described. Details of the construction, as well as of the evaluation of the apparatus are presented here. The performance of the test gas generator is validated both by on-line GC analysis of the calibration gas produced and by off-line analysis of adsorptive samples taken from the generated calibration gas. Both, active and passive sampling have been used, and the results demonstrate the excellent accuracy and precision of the generated test gas atmosphere: For the 11 investigated organic compounds (aromatic and halogenated compounds), the found values were in most cases within 5% of the target value with a reproducibility of better than 3% RSD (as determined by the analysis of the sampled adsorbent tubes). Custom made adsorbent tubes were used for active and passive sampling and in both cases were analysed by thermal-desorption GC. Particularly the combination of passive sampling and thermodesorption-GC analysis offers significant advantages over the commonly used active sampling on activated charcoal, followed by CS2 desorption in terms of avoidance of hazardous solvents, potential for automation and improved detection limits. Both sampling techniques are capable for monitoring VOCs at concentrations and under conditions relevant for workplace monitoring.     

顶空气相色谱-质谱法测定玩具中的10种挥发性有机物

建立了检测玩具中10种挥发性有机物(VOC)残留量的顶空气相色谱-质谱(HS-GC-MS)方法。样品经140 ℃、45 min静态顶空后,通过DB-624色谱柱分离和质谱检测,外标法定量。该方法对于不同VOC的定量限(LOQ)均在0.66 mg/kg以下,线性范围为0.001～2.0 μg,平均回收率在79%～106%之间,相对标准偏差(RSD)在0.4%～5.6%之间。该方法具有准确灵敏、简单快速等特点,将其应用于实际玩具样品的检测取得了良好效果。