顶空固相微萃取-气相色谱法测定生活饮用水中痕量1,4-二氧六环

建立了生活饮用水中痕量1,4-二氧六环的顶空固相微萃取(HS/SPME)-气相色谱测定方法。考察并优化了萃取头、萃取温度、萃取时间、pH值、样品量、色谱条件等参数。结果表明:提取效率较好的方法是3 mL水样中加入3 mL 600 g/L氢氧化钠溶液,用85 μm Carboxen-PDMS萃取头萃取,用键合碱改性的大口径、厚液膜PTA-5毛细管色谱柱测定。1,4-二氧六环在0.50~50.0 μg/L范围内线性关系良好,相关系数为0.9995;方法检出限(以S/N>3计)为0.14 μg/L;相对标准偏差为2.1%~4.5% (n=6);对实际样品中进行线性范围内的高、中、低3个加标水平的测定,回收率为95.5%~107%,相对标准偏差为1.1%~5.3% (n=6)。建立的方法简便、准确、重现性好、灵敏度高,适合生活饮用水中痕量1,4-二氧六环的常规监测。     

Liquid chromatography–mass spectrometry methods for urinary biomarker detection in metabonomic studies with application to nutritional studies

The effects of sample preparation and chromatographic method differences on the classification and recovery of metabolic biomarkers from UPLC‐MS measurements on urine samples of humans exposed to different dietary interventions have been investigated. Eight volunteers consumed three high‐fat meals (rich in saturated, monounsaturated and polyunsaturated fatty acids, respectively) in randomized order with a washout period in between. For each participant, urine samples were obtained prior to and at three timed intervals after each meal. Samples were processed either by dilution (1 : 4) or by liquid–liquid extraction and then run under two different gradient conditions. For each analysis method, a total of 96 observations (eight participants, four time points, three diets) were measured. The total ion count chromatograms were analyzed using partial‐least‐squares discriminant analysis. All three dietary classes could be discriminated irrespective of sample preparation and chromatographic method. However, the main discriminating metabolites varied according to sample preparation, indicating that sample treatment and chromatographic conditions influence the ability to extract biomolecular information. Diluted samples showed higher m/z compounds (ca 400 u) while liquid–liquid extraction samples showed low m/z at the same retention time span. Optimized methods for metabolite identification (e.g. organic acids) were statistically inferior to global screening for mixed compound identification, confirming that multiple compound class‐based metabolic profiles are likely to give superior metabonomic (diagnostic) classification, although great care has to be taken in the interpretation in relation to matrix effects. Copyright © 2009 John Wiley & Sons, Ltd.     

Urinary testosterone measurement by gas chromatography after solid-phase extraction and high-performance liquid chromatography.

A method was developed for the rapid determination of testosterone in urine. The procedure consists of solid-phase extraction (SPE) followed by high-performance liquid chromatographic (HPLC) clean-up before gas chromatographic determination. Recovery was evaluated by adding [3H]testosterone (10(4) cpm) to urine samples; the mean recovery of radioactivity after SPE and HPLC was 82%. Precision was estimated by repeated measurement of testosterone in four different urine samples; the coefficient of variation was 7.9% (95% confidence limits 6.1-11.4%). Accuracy was evaluated by standard addition and dilution assays; a linear relationship was found between the expected and observed values (r2 = 0.982). The method is rapid, effective and suitable for routine analysis.     

Determination of cigarette papers moisture content by gas chromatography

A method for the determination of the moisture content in cigarette papers using solvent extraction followed by gas chromatographic analysis was developed. Optimal extraction conditions, including the agitation method, solvent and extraction time, as well as optimal gas chromatographic parameters, such as the internal standard, were investigated. The maximum degree of moisture extraction was achieved when samples were soaked in 20 mL of ethanol containing 0.5 mL L^?1 of isopropanol as an internal standard for 50 min under ultrasonic agitation. The method showed good linearity over the concentration range from 0.26 mass % to 10 mass % of the moisture content with a correlation coefficient of 0.99998. The recovery (102.1–109.3 %) and precision (relative standard deviation: 1.64 %) of the method were examined by analyzing various cigarette paper samples. The method was successfully applied to different types of paper and it exhibits superior accuracy and high efficiency compared with the existing methods of moisture determination.     

微波萃取气相色谱法测定淀粉中14种有机氯农药残留

建立了淀粉中14种有机氯农药:六六六及滴滴涕的4种异构体、五氯硝基苯、四氯硝基苯、四氯苯胺、五氯苯胺、腐霉利、甲基五氯苯基硫醚(MPCPS)的微波辅助和气相色谱分析方法.优化了气相色谱检测条件,考察了提取方法、萃取条件、净化条件对提取效果的影响.目标农药在20～200 μg/kg范围内线性良好,平均回收率在68%～10...     

Liquid Chromatography Electrochemical Determination of Nicotine in Third‐Hand Smoke

Third‐hand smoke (THS) can be defined as the contamination of surfaces by second‐hand smoke. This residue can form further pollutants which can be re‐suspended in dust or be re‐emitted into the gas phase. THS is a complex mixture and as a result studies have focused on nicotine as a marker of THS, it being the most abundant and indicative organic compound deposited. In this present study, the extraction of dust wipe samples and the subsequent chromatographic conditions required for the separation of nicotine by liquid chromatography with electrochemical detection were investigated and optimised. The optimum chromatographic conditions were identified as a 150 mm×4.6 mm, 5 µm C₁₈ column with a mobile phase consisting of 65 % methanol, 35 % pH 8 20 mM phosphate buffer. Hydrodynamic voltammetry was used to optimise the applied potential which was identified to be +1.8 V (vs . stainless steel). Under these conditions, a linear range for nicotine of 13 to 3240 µg/L (0.26 ng–65 ng on column) was obtained, with a detection limit of 3.0 µg/L (0.06 ng on column) based on a signal‐to‐noise ratio of three. Dust wipe samples were extracted in methanol with the aid of sonication. Mean recoveries of 98.4 % (% CV=7.8 %) were found for dust wipe samples spiked with 6.50 µg of nicotine. Musk ketone, urea and stearic acid were found not to interfere. Communal entrance ways were found to be contaminated with THS nicotine levels of between 66.8 and 156 µg/m².     

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.     

A fully validated method for the determination of lacosamide in human plasma using gas chromatography with mass spectrometry: Application for therapeutic drug monitoring

A simple gas chromatographic method with mass spectrometry detection was developed and validated for the determination of lacosamide in human plasma. Lacosamide and the internal standard, levetiracetam‐d₆, were extracted from 200 μL plasma, by a solid‐phase extraction through HF Bond Elut C₁₈ columns, and derivatized using N‐methyl‐N‐tert‐butyldimethylsilyltrifluoroacetamide with 1% tert‐butyldimethylsilylchloride in acetonitrile. The limit of quantification was found to be 0.20 μg/mL and the assay was linear up to 20.0 μg/mL with correlation coefficient ≥0.994. The intra‐ and interday precision values were <4.1% in terms of relative standard deviation (%) and the values of intra‐ and interday accuracy were found to be within –7.2 and 5.3% in terms of relative error (%). Absolute recovery of the method for lacosamide was determined at three concentration levels and ranged from 92.5 to 97.6%. The developed method uses small volumes of plasma and proved to be simple, rapid, and sensitive for the determination of lacosamide in plasma. This method can be used in routine every day analysis of plasma samples obtained from patients who follow respective antiepileptic treatment and for the investigation of clinical and forensic cases where lacosamide is involved.     

Two polydimethylsiloxane rod extraction methods for the sensitive determination of phenolic compounds in water samples

Simple, precise, and low‐cost methods for the simultaneous determination of phenolic endocrine disrupting compounds such as bisphenol A, trichlorophenol, pentachlorophenol, 4‐nonylphenol, and 4‐octylphenol in water samples were developed. The Direct, in situ derivatization methods are based on polydimethylsiloxane rod extraction followed by liquid desorption and chromatographic analysis by liquid chromatography and diode array detection. Several parameters affecting the extraction and desorption of the phenolic compounds and their acetylated derivates were studied, as well as the chromatographic and detection conditions. For the direct method, determination coefficients (r²) > 0.990 and LODs in the 0.6–2 μg/L range were obtained for all compounds except bisphenol A (9.5 μg/L). With the derivatization‐based method, based on in situ acetylation, lower limits of detection (0.3–0.9 μg/L) were obtained for all the compounds with r² > 0.988 and RSDs in the 2–9% range. The developed methods were applied to the analysis of spiked water samples obtaining recoveries of between 60.2 and 131.7% for the direct method, and of between 76.6 and 108.2% for the derivatization‐based method. The results demonstrate the feasibility of using these two methods for determining bisphenol A, trichlorophenol, pentachlorophenol, 4‐nonylphenol, and 4‐octylphenol in water.     

An evaluation method for determination of non-polar pesticide residues in animal fat samples by using dispersive solid-phase extraction clean-up and GC-MS

A rapid and easy method has been proposed, optimized and evaluated for quantitative determination at trace level of a representative group of non-polar pesticides in fat samples. The method includes n-hexane-saturated acetonitrile extraction, fat precipitation by cooling pre clean-up followed by dispersive solid-phase extraction (d-SPE) based on QuEChERS procedure clean-up. Determination was performed by gas chromatography?Cmass spectrometry (GC-MS) in selected ion monitoring (SIM) mode. Efficiency of the d-SPE clean-up step was evaluated by comparison with fat oxidation treatment and gel permeation chromatography. Different combinations of d-SPE extraction reagents and sample amounts were tested in order to minimize matrix co-extractives and interferences. Best recoveries were obtained with 1200?mg of MgSO₄, 400?mg of end-capped C₁₈, 400?mg of PSA and 1?g of sample amount. SIM method, matrix effect, precision, and accuracy were evaluated with spiked pork fat samples for 38 representative pesticides. Results of this study showed that this technique is applicable in routine analysis for its application into monitoring programs. It simplifies time-consuming clean-up steps and allows a satisfactory long-term chromatographic performance.     

Development of a multiresidue method for the determination of multiclass pesticides in soil using GC

The principal objective of the present study was to develop a multiresidue analytical method for 62 pesticides in a soil matrix. Soil samples were fortified with known quantities of pesticides at two different concentration levels (0.1 and 0.01 μg/g) and the analytes were extracted via a liquid–solid extraction method. The pesticides were separated on an HP5 capillary column and were detected by gas chromatography coupled to an electron capture detector (GC‐ECD). The method was validated, considering its good linearities (r² = 0.978–0.999), specificity and recovery characteristics. Recoveries were found between 70.3 and 113.4% for all pesticides except edifenphos (67.5%) and dichlobenil (69.5%) spiked at a 0.1 μg/mL concentration level and 74.5–117% except ethalfluralin (63.3%) and dichlobenil (51.9%) spiked at a concentration of 0.01 μg/mL. The developed method could be utilized as a simple and cost‐effective method for the routine analysis of 62 pesticides in soil samples. Copyright © 2009 John Wiley & Sons, Ltd.     

Accelerated solvent extraction combined with dispersive liquid–liquid microextraction before gas chromatography with mass spectrometry for the sensitive determination of phenols in soil samples

A method combining accelerated solvent extraction with dispersive liquid–liquid microextraction was developed for the first time as a sample pretreatment for the rapid analysis of phenols (including phenol, m‐cresol, 2,4‐dichlorophenol, and 2,4,6‐trichlorophenol) in soil samples. In the accelerated solvent extraction procedure, water was used as an extraction solvent, and phenols were extracted from soil samples into water. The dispersive liquid–liquid microextraction technique was then performed on the obtained aqueous solution. Important accelerated solvent extraction and dispersive liquid–liquid microextraction parameters were investigated and optimized. Under optimized conditions, the new method provided wide linearity (6.1–3080 ng/g), low limits of detection (0.06–1.83 ng/g), and excellent reproducibility (<10%) for phenols. Four real soil samples were analyzed by the proposed method to assess its applicability. Experimental results showed that the soil samples were free of our target compounds, and average recoveries were in the range of 87.9–110%. These findings indicate that accelerated solvent extraction with dispersive liquid–liquid microextraction as a sample pretreatment procedure coupled with gas chromatography and mass spectrometry is an excellent method for the rapid analysis of trace levels of phenols in environmental soil samples.     

Analysis of sulthiame in serum by narrow-bore high-performance liquid chromatography. Comparison of direct sample injection with pre-column switching and extrelut extraction.

Two high-performance liquid chromatographic methods for the analysis of sulthiame in serum are described. In the first method direct injection of serum samples onto a 4 x 4 mm I.D. (C18, 25 microns) precolumn in a column-switching device was used. After a purge step, the adsorbed analytes were eluted onto a 250 x 3 mm I.D. (C18, 5 microns) narrow-bore column for chromatographic separation. In the second method the sample pretreatment was an Extrelut extraction with dichloromethane-propanol-2 (95:5). After evaporation of the solvents, the residue was dissolved in methanol. The chromatographic separation was carried out on the same analytical column as used in the column-switching method. Both sample pretreatment methods were compared with respect to their suitability of routine analysis of sera from patients also receiving other antiepileptic drugs.     

Rapid analysis of pyrethroid insecticides in aquaculture seawater samples via membrane-assisted solvent extraction coupled with gas chromatography-electron capture detection

A simple, efficient, and environmentally friendly membrane-assisted solvent extraction (MASE) method for the extraction and preconcentration of six pyrethroid insecticides from aquaculture seawater samples followed by gas chromatography-electron capture detection (GC-ECD) was successfully proposed. The operating conditions for MASE, such as the extraction solvent, solvent volume, NaCl concentration, stirring rate, extraction time, and temperature, were optimized. Compared to conventional Florisil-solid phase extraction (SPE), higher extraction recoveries (85.9% to 105.9%) of three spiked levels of the six pyrethroid pesticides in aquaculture seawater were obtained using MASE, and the RSD values were lower than 7.9%. The limits of detection (LOD, signal-to-noise ratio (S/N)=3) and quantification (LOQ, S/N = 10) were in the range of 0.037-0.166 and 0.12-0.55 μg L(-1), respectively. The results demonstrate the excellent applicability of the MASE method in analyzing the six pyrethroid pesticides in aqueous samples. The proposed method exhibited a high potential for routine monitoring analysis of pyrethroid insecticides in seawater samples.     

Dispersive liquid-liquid microextraction and gas chromatography-mass spectrometry determination of polychlorinated biphenyls and polybrominated diphenyl ethers in milk

An effective multi‐residue pretreatment technique, solid‐phase extraction (SPE) combined with dispersive liquid–liquid microextraction (DLLME), was proposed for the trace analysis of 14 polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs) in milk samples using gas chromatography–mass spectrometry (GC‐MS). Interesting analytes in milk samples were extracted with hexane after protein precipitation. The hexane extracts were loaded on an LC‐Florisil column to isolate analytes from the milk matrix. The elutes were dried and dissolved in acetone, which was used as the disperser solvent in subsequent DLLME procedures. The effects of several important parameters on the extraction efficiency were evaluated. Under the optimized conditions, a linear relationship was obtained in the range of 0.02–10.00 μg/L (PCBs) and 0.5–100.00 μg/L (PBDEs). The LOD (S/N=3) and relative standard deviations (RSDs, n=5) for all analytes were 0.01–0.4 μg/L and 0.6–8.5%, respectively. The recoveries of the standards added to raw bovine milk samples were 74.0–131.8%, and the repeatabilities of the analysis results were 1.12–17.41%. This method has been successfully applied to estimating PCBs and PBDEs in milk samples.     

气相色谱-质谱联用法测定食品中3-氯丙醇酯及缩水甘油酯

建立了气相色谱-质谱联用同时测定多种植物油和油脂类食品中3-氯丙醇酯(3-MCPDE)和缩水甘油酯(GE)的检测方法。通过对样品提取、酯交换、衍生化和GC-MS检测条件的优化,植物油、奶粉、油炸膨化类食品以及焙烤类食品中3-MCPDE的定量下限分别为100、25、125、20μg/kg。方法的平均回收率为81.2%~109%,相对标准偏差(RSD,n=6)为0.77%~7.3%,样品在较宽的线性范围内呈良好线性关系,相关系数(r)大于0.999。采用该方法对30个食品样品进行了检测,其中3-MCPDE和GE的检出含量范围为未检出~8.04 mg/kg。该法具有高效、灵敏和可操作性强等特点,能够满足日常食品,特别是油脂和油脂食品中3-MCPDE和GE的定性及定量检测要求。     

Rapid and sensitive determination of two degradation products of flumethrin in honey by ultrasonically assisted extraction and gas chromatography with electron capture detection

A rapid and sensitive method for the determination of 4-fluoro-3-phenoxybenzaldehyde cyanohydrin (FPBC) and 4-fluoro-3-phenoxy-benzaldehyde (FPB) in honey samples using ultrasonically assisted extraction and gas chromatography with electron capture detection (GC-ECD) has been developed. The different factors affecting the efficiency of the extraction were carefully optimized. The honey sample was extracted with a mixture of hexane and dichloromethane (v/v, 1:1) utilizing the ultrasonically assisted technique and cleaned up by solid-phase extraction on Oasis HLB cartridges. The eluate was evaporated to dryness and residues were reconstituted to 1.0 mL with hexane and determined by GC-ECD. The calibration curves of fortified samples showed acceptable linear response (R(2) >0.99) over a range of 3-100 ng/g for FPBC and FPB in seven replicate determinations of six concentrations, respectively, and analysis of variance (ANOVA) with a lack-of-fit test was performed to validate the regression data. Overall average recoveries ranged from 90.9 to 106.2% for honey samples. The detection limits were 0.9 ng/g for FPBC and 1.0 ng/g for FPB, respectively. This method can be successfully applied to routine determination of two degradation products of flumethrin in honey samples.     

Improved method for extraction of aroma compounds in aged brandies and aqueous alcoholic wood extracts using ultrasound

This work presents a rapid method for dichloromethane extraction of aroma compounds from brandies and aqueous-alcoholic wood extracts, in brandy-like ageing conditions, using ultrasound. The dichloromethane extracts were injected in split mode on a gas chromatographic (GC) system, separated on a DB-WAX capillary column and detected by flame ionisation. The method allowed satisfactory quantification of 37 volatile compounds in brandies (alcohols, esters, acids, furanics, aldehydes and phenols) and 16 volatile compounds in aqueous-alcoholic oak extracts. Linear responses were obtained (0.99-1.00). The repeatability and the detection and quantification limits were also evaluated. The analysis of spiked samples showed that matrix effects do not affect the method performance for the majority of the volatile compounds analysed.     

Solid‐phase microextraction of phthalate esters by a new coating based on a thermally stable polypyrrole/graphene oxide composite

A novel polypyrole/graphene oxide coating was made by the electrochemical polymerization of pyrrole in the presence of sodium dodecyl sulfate and graphene oxide on a platinum wire. The prepared fiber has shown a good thermal stability up to 300°C. The fiber was applied to the direct solid‐phase microextraction and gas chromatographic analysis of four phthalate esters. The effect of four parameters on gas chromatography peak area including extraction temperature, extraction time, injection temperature, and ionic strength were investigated. Under the optimized conditions, the detection limits were between 0.042 and 0.26 μg/L. The intraday and interday relative standard deviations obtained at 55 μg/L, using a single fiber, were 8.2–16% and 17.3–25.6%, respectively. The method was successfully applied to the analysis of phthalate esters in two real samples of boiling water in cheap disposable clear plastic drinking cups showing recoveries from 83 to 120%.     

Determination of polybrominated diphenyl ethers in domestic dust by microwave-assisted solvent extraction and gas chromatography-tandem mass spectrometry

In this paper, a rapid and simple method for the analysis of polybrominated diphenyl ethers (PBDEs) in house dust samples based on microwave-assisted solvent extraction (MASE) and gas chromatography-tandem mass spectrometry (GC-MS/MS) is presented. Extraction conditions were optimized using a multifactorial experimental design approach. The use of an aqueous NaOH phase in combination with a non-polar organic phase (hexane) to extract the target analytes from dust allowed an efficient extraction and reduced chromatographic background. The final hexane extracts could be analyzed after a simple one-step cleanup procedure using Florisil. The validation of the method was performed in terms of accuracy, linearity, and repeatability. The limits of detection (LODs) ranged from 0.29 to 0.55 ng/g for all compounds. The target PBDEs were found in several real dust samples collected in urban and rural houses of Northwestern Spain.