Analysis of poly-β-hydroxybutyrate in environmental samples by GC-MS/MS

Application of gas chromatography-mass spectrometry (GC-MS) can significantly improve trace analyses of compounds in complex matrices from natural environments compared to gas chromatography only. A GC-MS/MS technique for determination of poly-β-hydroxybutyrate (PHB), a bacterial storage compound, has been developed and used for analysis of two soils stored for up to 319 d, fresh samples of sewage sludge, as well as a pure culture of Bacillus megaterium. Specific derivatization ¶of β-hydroxybutyrate (3-OH C_4?:?0) PHB monomer units by N-tert-butyl-dimethylsilyl-N-methyltrifluoracetamide (MTBSTFA) improved chromatographic and mass spectrometric properties of the analyte. The diagnostic fragmentation scheme of the derivates tert-butyldimethylsilyl ester and ether of β-hydroxybutyric acid (MTBSTFA-HB) essential for the PHB identification was shown. The ion trap MS was used, therefore the scan gave the best sensitivity and with MS/MS the noise decreased, so the S/N was better and also with second fragmentation the amount of ions increased compared to SIM. The detection limit for MTBSTFA-HB by GC-MS/MS was about 10^–13 g μL^–1 of injected volume, while by GC (FID) and GC-MS (scan) it was around 10^–10 g μL^–1 of injected volume. Sensitivity of GC-MS/MS measurements of PHB in arable soil and activated sludge samples was down to 10 pg of PHB g^–1 dry matter. Comparison of MTBSTFA-HB detection in natural soil sample by GC (FID), GC-MS (scan) and by GC-MS/MS demonstrated potentials and limitations of the individual measurement techniques.     

Dispersive liquid-liquid microextraction method based on solidification of floating organic drop combined with gas chromatography with electron-capture or mass spectrometry detection

A simple dispersive liquid-liquid microextraction (DLLME) method based on solidification of a floating organic drop (DLLME-SFO) technique combined with gas chromatography/electron-capture detection (GC/ECD) or gas chromatography/mass spectrometry (GC/MS) has been developed. The proposed method is simple, low in cost, and of high precision. It overcomes the most important problem in DLLME, the high-toxic solvent used. Halogenated organic compounds (HOCs) in water samples were determined as the model compounds. The parameters optimized for the DLLME-SFO technique were as follows: A mixture of 0.5 mL acetone, containing 10 microL 2-dodecanol (2-DD-OH), was rapidly injected by syringe into the 5 mL water sample. After centrifugation, the fine 2-DD-OH droplets (8+/-0.5 microL) were floated at the top of the screwcap test tube. The test tube was then cooled in an ice bath. After 5 min the 2-DD-OH solvent had solidified and was then transferred into a conical vial; it melted quickly at room temperature and 3 microL (for GC/ECD) or 2 microL (for GC/MS) of it was injected into a gas chromatograph for analysis. The limit of detection (LOD) for this technique was 0.005-0.05microgL(-1) for GC/ECD and was 0.005-0.047 microgL(-1) for GC/MS, respectively. The linear range of the calibration curve of DLLME-SFO was from 0.01 to 500 microgL(-1) with a coefficient of estimation (r2)>0.996 for GC/ECD and was from 0.02 to 500 microgL(-1) with a coefficient of estimation (r2)>0.996 for GC/MS.     

气相色谱/氢火焰离子化检测法分析烷基化物料中的C4氟代烃

以实验室合成的氟代叔丁烷、氟代仲丁烷、氟代正丁烷为参考,建立了烷基化物料中C4氟代烃的气相色谱/氢火焰离子化检测(GC/FID)分析方法。提出了利用气相色谱/原子发射光谱(GC/AED)按元素响应的特点求算C4氟代烃在GC/FID上相对校正因子的方法。方法采用OV-225(50 m×0.25 mm i.d.×0.25 μm)和SE-54(44 m×0.22 mm i.d.×0.25 μm)串联柱为分析柱,FID为检测器,校正归一化或间接外标方法进行定量,具有重复性好、应用移植便利、操作简单等特点,对氟代叔     

Dispersive liquid–liquid microextraction using extraction solvent lighter than water

For the first time a dispersive liquid–liquid microextraction method on the basis of an extraction solvent lighter than water was presented in this study. Three organophosphorus pesticides (OPPs) were selected as model compounds and the proposed method was carried out for their preconcentration from water samples. In this extraction method, a mixture of cyclohexane (extraction solvent) and acetone (disperser) is rapidly injected into the aqueous sample in a special vessel (see experimental section) by syringe. Thereby, a cloudy solution is formed. In this step, the OPPs are extracted into the fine droplets of cyclohexane dispersed into aqueous phase. After centrifuging the fine droplets of cyclohexane are collected on the upper of the extraction vessel. The upper phase (0.40 μL) is injected into the gas chromatograph (GC) for separation. Analytes were detected by a flame ionization detector (FID) (for high concentrations) or MS (for low concentrations). Some important parameters, such as the kind of extraction and dispersive solvents and volume of them, extraction time, temperature, and salt amount were investigated. Under the optimum conditions, the enrichment factors (EFs) ranged from 100 to 150 and extraction recoveries varied between 68 and 105%, both of which are relatively high over those of published methods. The linear ranges were wide (10–100 000 μg/L for GC‐FID and 0.01–1 μg/L for GC‐MS) and LODs were low (3–4 μg/L for GC‐FID and 0.003 μg/L for GC‐MS). The RSDs for 100.0 μg/L of each OPP in water were in the range of 5.3–7.8% (n = 5).     

Determination of Atenolol in Pharmaceutical Preparations by Gas Chromatography with Flame Ionization and Mass Spectrometric Detection

The present work describes the methodology and validation of gas chromatography with flame ionization (FID) and mass spectrometric (MS) detection after derivatization with N-Methyl-N-(trimethylsilyl)trifluoroacetamide (MSTFA) for determination of atenolol with an internal standard (metoprolol) in pharmaceutical preparations. The linearity was established over the concentration range of 0.5–20 μg/mL for GC/FID and 12.5–500 ng/mL for GC/MS method. The intra- and inter-day relative standard deviation was less than 4.72 and 5.80%, respectively. Limit of quantification was determined as 500 ng/mL and 12.5 ng/mL for GC/FID and GC/MS, respectively. No interference was found from tablet excipients at the selected assay conditions. Developed GC/FID and GC/MS methods in this study are accurate, sensitive, and precise and can be easily applied to Tensinor tablet as pharmaceutical preparation.     

Comparison of different mass spectrometric detection techniques in the gas chromatographic analysis of pyrethroid insecticide residues in soil after microwave-assisted extraction

A comparative study was carried out for the simultaneous determination of 11 pyrethroid insecticides in soil by gas chromatography (GC) - ion trap (IT)- mass spectrometry (MS), by means of two different ionization modes; electron impact and negative chemical ionization and three data acquisition procedures; full scan, selected ion monitoring and MS/MS. Pyrethroids investigated were tetramethrin, bifenthrin, phenothrin, λ-cyhalothrin, permethrin, cyfluthrin, cypermethrin, flucythrinate, esfenvalerate, fluvalinate and deltamethrin. Soil samples were treated with toluene/water by microwave-assisted extraction for 9 min at 700 W and a cleaning up with florisil was performed. Clean soil samples were spiked with pyrethroids at a spiking level of 10, 25 and 50 ng/g. The method employed provides a concentration factor of 10. The ionization gas employed in the negative chemical ionization mode was methane. The use of MS/MS acquisition, in electron impact ionization, provided the best results, due to its high selectivity and sensitivity, giving very low limits of detection from 0.08 to 0.54 ng/g. In negative chemical ionization full scan and selected ion monitoring methods detection limits from 0.12 to 1.40 ng/g were found. The proposed methods were applied to several levels from 10 to 50 ng/g of spiked soils, being electron impact MS/MS method which minimizes matrix spectrum interferences and provided recovery average values from 84% to 120% with relative standard deviations which varied from 3.2 to 7.2%.     

大体积进样技术在气相色谱-质谱法测定 二英类化合物中的应用

利用大体积进样技术(large volume injection,LVI),结合气相色谱-质谱方法对二英的测定效果进行了研究。同时与传统分流/不分流进样技术进行了对比。对进样体积为1,5,10,25,50和100 μL的色谱图进行了分析。研究表明使用大体积进样方式,在不影响色谱分离度的同时,大幅度提高了分析灵敏度。通过对土壤样品的检测,证明该方法可以用于环境样品的实际测定。     

Rapid and Simple Methods for Determination of Medazepam in Pharmaceutical Preparations using GC-FID and GC-MS

Abstract

This paper describes two rapid, sensitive, and specific methods for the determination of medazepam with internal standard (diazepam) in pharmaceutical preparations by gas chromatography (GC) with flame ionization (FID) and mass spectrometric (MS) detection. The linearity was established over the concentration range of 0.25–5 µg/mL for GC-FID and 50–1000 ng/mL for GC-MS method. The intra- and inter-day relative standard deviation was less than 2.94 and 4.95%, respectively. Developed GC-FID and GC-MS methods in this study are accurate, sensitive, and precise and can be directly and easily applied to Tranko buskas as pharmaceutical preparation.     

Simplified sample preparation method for triclosan and methyltriclosan determination in biota and foodstuff samples

An improved method for the determination of triclosan (TCS) and methyltriclosan (MTCS) in fish and foodstuff samples is presented. Analytes were simultaneously extracted and purified using the matrix solid-phase dispersion (MSPD) technique, and then selectively determined by gas chromatography with tandem mass spectrometry (GC-MS/MS). Several combinations of dispersants, clean-up co-sorbents and extraction solvents were tested in order to obtain lipid-free extracts and quantitative recoveries for TCS and MTCS. Under optimised conditions, 0.5 g samples were dispersed using 1.5 g of neutral silica in a mortar with a pestle, and transferred to a polypropylene cartridge containing 3 g of silica impregnated with 10% of sulphuric acid (SiO2-H2SO4, 10%, w/w). Analytes were recovered with 10 mL of dichloromethane whereas lipids were oxidized in the layer of acidic silica. The extract was concentrated to dryness and re-constituted with 1 mL of ethyl acetate. Then, a fraction of 0.5 mL was mixed with 50 microL of N-methyl-N-(tert-butyldimethylsilyl)trifluoroacetamide (MTBSTFA) and injected in the GC-MS/MS system. The developed method provided absolute recoveries between 77 and 120% for different samples spiked at the low ng g(-1) level, quantification limits in the range of 1-2 ng g(-1) and a considerable simplicity in comparison with previously developed sample preparation approaches. Experiments carried out placing sliced food samples in direct contact with TCS-treated kitchenware surfaces showed the capability of the biocide to migrate into foodstuffs.     

Simultaneous use of gas chromatography/ion trap mass spectrometry - electron capture detection to improve the analysis of bromodiphenyl ethers in biological and environmental samples

Bromodiphenyl ethers (BDEs) are a class of synthetic flame retardants and are widely present in the environment. Analysis of higher BDE congeners has proven to be a challenge. We report the development of a method that enhances their analysis by splitting the eluent of a gas chromatograph (GC) between an electron capture detector (ECD) and an ion trap mass spectrometer (ITMS): 1:10, ECD:ITMS. This allowed the quantitation of the lower molecular weight (MW) BDE congeners (Br1-Br7) with the ITMS and of the higher MW BDEs (Br8-Br10) with the highly sensitive ECD. The IT temperature, ionization mode, and MS/MS parameters (excitation amplitude and stability parameter) were optimized. This method took the advantages of the best detector for the different BDE homologues and was suitable for the analysis of BDEs in environmental and biological samples. Average recoveries were 52-112% for BDEs from spiked sand samples and 57-126% from spiked lard samples after accelerated solvent extraction followed by silica gel and alumina column clean-up. Average recoveries ranged from 51% to 130% for 13C-labeled BDEs spiked in the real and in matrix samples. The method detection limits for specific congeners were 0.18-120 pg/g of the BDEs in animal tissue samples, and 0.05-40 pg/g in soil and indoor dust samples. The utility of the method was demonstrated by analyzing actual harbor seal blubber, indoor dust and soil samples. The concentration of each BDE ranged from non-detectable (nd) to 41 ng/g in the dry soil sample, nd to 1042 ng/g in the indoor dust, nd to 15 ng/g wet weight in the Alaskan harbor seal blubber sample, and 0.02 to 11 ng/microL of the identified 23 of the 42 breakdown products from BDE-209 after zerovalent iron treatment. Finally, an interlaboratory comparison showed high correspondence between the GC/ITMS-ECD method and a GC high-resolution MS system for the analysis of BDEs in soil samples.     

大气环境中挥发性有机化合物的测定

 参考美国环保局大气中挥发性有机化合物 (VOCs)的标准分析方法TO14A和TO15 ,采用预浓缩器与气相色谱联用 ,以质谱或氢火焰离子化检测器检测 ,建立了 5 6种VOCs(主要是臭氧前体物 )的快速分析方法。该方法在同一台仪器上采用单柱、单检测器 ,准确测定了高浓度CO2 下的VOCs。方法检出限为 0 1μg·m-3 ,相对标准偏差(RSD)为 2 5 7%～ 9 82 %。用该法分析了实际大气样品中的VOCs,结果令人满意。     

Qualitative and quantitative determination of extractives in heartwood of Scots pine (Pinus sylvestris L.) by gas chromatography

A method for quantitative determination of extractives from heartwood of Scots pine (Pinus sylvestris L.) using gas chromatography (GC) with flame ionization detection (FID) was developed. The limit of detection (LOD) was 0.03 mg/g wood and the linear range (r = 0.9994) was up to 10 mg/g with accuracy within +/- 10% and precision of 18% relative standard deviation. The identification of the extractives was performed using gas chromatography combined with mass spectrometry (GC-MS). The yields of extraction by Soxhlet were tested for solid wood, small particles and fine powder. Small particles were chosen for further analysis. This treatment gave good yields of the most important extractives: pinosylvin, pinosylvin monomethyl ether, resin acids and free fatty acids. The method is used to demonstrate the variation of these extractives across stems and differences in north-south direction.     

Analysis of volatile varnishes of coated wires by SPME

Metal wires coated with varnishes emit organic compounds with increasing of temperature. The use of headspace-GC/MS in the full scan modus is required to identify these compounds. Solid phase microextraction (SPME) allows to analyze the emissions by GC/MS. The response for headspace/SPME-GC/MS is larger than for headspace-GC/FID although the FID detector is very sensitive.     

Selective and sensitive trace analysis of sulfur mustard with thermal desorption and two-dimensional gas chromatography-mass spectrometry

An improved method is presented for the trace analysis of sulfur mustard (HD) in biological samples, such as blood and tissue from laboratory animals. Using the internal standard method and liquid-liquid extraction with ethyl acetate, up to 400 microL of the extract was injected by thermal desorption from Tenax and analyzed by two-dimensional GC-MS/EI in SIM mode. The analysis was compared with a direct GC injection. Reversed thermal desorption was used as a tool for handling heavily contaminated (fat) samples, thus preventing contamination of the injection system and pre-column. A successful analytical configuration has been set up for the bioanalysis of HD at the low, toxicologically relevant pM level. A detection limit of 10 pg mL(-1) blood or pg g(-1) tissue of sulfur mustard (S/N=3) was established by using this configuration.     

Solid-phase microextraction-gas chromatographic determination of volatile monoaromatic hydrocarbons in soil

Benzene, toluene, ethylbenzene, three isomers of xylene, and cumene have been isolated and enriched from soil samples by a combination of water extraction at room and elevated temperature and headspace-solid-phase microextraction before their gas chromatographic-mass spectrometric (GC-MS) determination. The conditions used for all stages of sample preparation and chromatographic analysis were optimized. Analytes sampled on a polydimethylsiloxane-coated solid-phase microextraction fiber were thermally desorbed in the split/splitless injector of a gas chromatograph (GC) coupled with a mass spectrometer (MS). The desorption temperature was optimized. The GC separation was performed in a capillary column. Detection limits were found to be of the order of ca. 1 ng g(-1). Relative recoveries of the analytes from soils were found to be highly dependent on soil organic-matter content and on compound identity; they ranged from ca 92 to 96% for sandy soil (extraction at room temperature) and from ca 27 to 55% for peaty soil (extraction at elevated temperature). A few real-world soil samples were analyzed; the individual monoaromatic hydrocarbon content ranged from below detection limits to 6.4 ng g(-1) for benzene and 8.1 for the total of p- + m-xylene.     

Identification, quantitation and method validation for the analysis of suspected allergens in fragrances by comprehensive two-dimensional gas chromatography coupled with quadrupole mass spectrometry and with flame ionization detection

The first part of this study first aims at validating a method to identify suspected allergens limited by EU regulations in fragrances by comprehensive two-dimensional gas chromatography (GC x GC) coupled with rapid scanning quadrupole MS (GC x GC-qMS). The effectiveness of the quadrupole MS operating at different scanning speed (1000 and 11,111 amu/s) was evaluated in identifying (full scan mode acquisition--TIC) and in quantifying (single ion monitoring--SIM) the target analytes in complex mixtures. In full scan acquisition mode the mass range was reduced to 40-240 amu to increase the scan acquisition rate while in SIM mode the influence of different dwell-times (40, 10 and 5 ms) was tested. The number of scans for each single modulated chromatographic GC x GC peak and the total number of scans for the 2D peak, together with half height peak width (referred to apex) of each allergen in the standard mixture in both TIC and SIM modes were determined. Moreover, the match quality of the spectra obtained by GC/MS at 1000 and 11,111 amu/s and by GC x GC-MS at 11,111 amu/s were compared and the occurrence of spectral skewing verified. In the second part of this work quantitative methods by GC x GC-SIM/qMS and GC x GC-FID were validated on the basis of Eurachem/CITAC protocols through which the following performance parameters were determined: confirmation of identity, selectivity and specificity, limit of detection (LOD), limit of quantitation (LOQ), linearity (working and linear range), precision and accuracy and uncertainty. Suspected allergens were spiked in a concentration range between 2 and 25 ppm (microg/mL) on a Test fragrance taken as a reference, while 1,4 dibromo-benzene and 4,4'-dibromodiphenyl were used as internal standards.     

Development and validation of a gas chromatography/mass spectrometry metabonomic platform for the global profiling of urinary metabolites

This paper presents a simple and reliable gas chromatography/mass spectrometry (GC/MS) method for the metabonomic analysis of human urine samples. The sample preparation involved the depletion of excess urea via treatment with urease and subsequent protein precipitation using ice-cold ethanol. An aliquot of the mixture was separated, dried, trimethylsilyl (TMS)-derivatized and 1.0 microL of the derivatized extract was injected into the GC/MS system via split injection (1:10). Approximately 150 putative metabolites belonging to different chemical classes were identified from the pooled human urine samples. All the identified metabolites were selected to evaluate precision and stability of the GC/MS assay. More than 95% of the metabolites demonstrated good reproducibility, with intra-day and inter-day precision values below 15%. Metabolic profiling of 53 healthy male and female urine samples in combination with pattern recognition techniques was performed to further validate the GC/MS metabolite profiling assay. Principal component analysis (PCA) followed by orthogonal partial least squares analysis (OPLS) revealed differences between urinary metabolite profiles of healthy male and female subjects. This validated GC/MS metabolic profiling method may be further applied to the metabonomic screening of urinary biomarkers in clinical studies. Copyright (c) 2008 John Wiley & Sons, Ltd.     

GC-FID/MS method for the impurity profiling of synthetic d-allethrin

A GC/FID/MS method was developed for the identification and quantification of d-allethrin (DA) and its major impurities in commercial samples. Optimisation of the experimental conditions was carried out considering such important requirements as resolution, reproducibility, detection limits of 0.1% (m/m) for the impurities, and short analysis time. Under the optimised final conditions the method was validated for specificity, precision (CV% = 0.133 at 2.10 mg/mL and CV% = 0.035 at 3.00 mg/mL), linearity (0-3.00 microg injected), limits of detection (0.09 ng injected) and quantitation (0.28 ng injected), and robustness. The DA related impurities were identified by using a GC/MS method with ion trap mass detection and also by comparison with synthesised standards. The most abundant impurities were crysolactone, allethrolone, chrysanthemic acid, and chloro-derivatives of DA.     

Analysis of volatile varnishes of coated wires by SPME

Metal wires coated with varnishes emit organic compounds with increasing of temperature. The use of headspace-GC/MS in the full scan modus is required to identify these compounds. Solid phase microextraction (SPME) allows to analyze the emissions by GC/MS. The response for headspace/SPME-GC/MS is larger than for headspace-GC/FID although the FID detector is very sensitive. Received: 1 December 1998 / Revised: 11 January 1999 / Accepted: 15 January 1999     

Flow modulation comprehensive two-dimensional gas chromatography-mass spectrometry with a supersonic molecular beam

A new approach of flow modulation comprehensive two-dimensional gas chromatography-mass spectrometry (GC x GC-MS) with supersonic molecular beam (SMB) and a quadrupole mass analyzer is presented. Flow modulation uniquely enables GC x GC-MS to be achieved even with the limited scan speed of quadrupole MS, and its 20 ml/min column flow rate is handled, splitless, by the SMB interface. Flow modulation GC x GC-SMB-MS shares all the major benefits of GC x GC and combines them with GC-MS including: (a) increased GC separation capability; (b) improved sensitivity via narrower GC peaks; (c) improved sensitivity through reduced matrix interference and chemical noise; (d) polarity and functional group sample information via the order of elution from the second polar column. In addition, GC x GC-SMB-MS is uniquely characterized by the features of GC-MS with SMB of enhanced and trustworthy molecular ion plus isotope abundance analysis (IAA) for improved sample identification and fast fly-through ion source response time. The combination of flow modulation GC x GC with GC-MS with SMB (supersonic GC-MS) was explored with complex matrices such as diesel fuel analysis and pesticide analysis in agricultural products.