Determination of beer aroma compounds using headspace solid-phase microcolumn extraction

A rapid sampling technique for the analysis of beer aroma compounds is described. The headspace (10 ml) is passed through the microcolumn filled with 5 mg of Tenax TA and thermally desorbed in a modified GC inlet (modification is described). Eight compounds (from acetaldehyde to 2-phenylethanol) in four beer samples were analyzed. The correlation coefficients (r²), repeatability (RSD) and limits of detection (LOD) were 0.9973-0.9994, 2.1-6.9% and 0.00002-0.13 mg/l, respectively. The methodology can be useful for routine beer sample analysis.     

顶空液相微萃取测定溶剂型涂料中挥发性有机物

应用顶空液相微萃取法对溶剂型涂料中的挥发性有机物(VOC)进行分离富集,直接进样气相色谱法分析。对萃取溶剂进行了筛选,并研究了平衡温度、溶剂体积、萃取时间等影响因素对萃取效率的影响。在优化的条件下,苯、甲苯、二甲苯、三氯乙烯和四氯乙烯的检出限分别为0.25、0.25、0.75、1.25和1.75μg/L。进行了方法的准确度和精密度试验,平均回收率为94.14%~119.33%,相对标准偏差为2.9%~18.9%。     

Determination of Henry''s law coefficients by combination of the equilibrium partitioning in closed systems and solid-phase microextraction techniques

This paper describes the determination of Henry's law coefficients by means of the EPICS (equilibrium partitioning in closed systems) technique in combination with SPME (solid-phase microextraction). The use of solid-phase microextraction-sampling allowed us to extend the possibilities of the equilibrium partitioning in closed systems technique with respect to the range of Henry's law coefficients which can be measured. Whereas the equilibrium partitioning in closed systems technique is limited to determine air–water equilibrium partitioning of volatile compounds with Henry's law coefficients of at least 0.06 (dimensionless), the current method allowed to measure coefficients between 0.0023 and 13.5. In this way Henry's law coefficients of 20 compounds, being in a range covering five orders of magnitude, were measured with relative standard deviations between 1.0 and 19.8% (mean standard deviation: 5.7%; median of standard deviations: 4.8%, n=99). Several types of compounds were examined i.e. aliphatic hydrocarbons, monocyclic and polycyclic aromatic hydrocarbons, chlorinated and fluorinated compounds, ethers and esters, biphenyl and N-containing compounds, including compounds for which availability of experimental Henry's law coefficients is limited. Measurement of the equilibrium partitioning in the 2 to 25°C range allowed to establish relations of Henry's law coefficient as a function of temperature.     

Solid phase microextraction using fused silica fibers coated with graphitized carbon black

Summary This paper presents the results obtained using fused-silica fibers coated with graphitized carbon black (Carbograph-Alltech) for solid-phase microextraction (SPME). The extraction and calibration curves relative to organic micro-pollutants present in gaseous and aqueous samples are reported. Examples of applications of this extraction procedure to GC and GC-MS analysis of organic micro-pollutants in actual samples are also reported.     

Determination of the fungicides vinclozolin and dicloran in soils using ultrasonic extraction coupled with solid-phase microextraction

Solid-phase microextraction (SPME) coupled to ultrasonic extraction was evaluated for extracting trace amounts of two agrochemical fungicides, vinclozolin and dicloran, in soil samples. Extraction was performed following two experimental approaches prior to the submission of the aqueous extracts to SPME-GC analysis. In the first approach, extraction involved sample homogenization with a water solution containing 5% (v/v) acetone and centrifugation prior to fiber extraction. In the second approach, the extraction of the fungicides from the soil samples was conducted using acetone as organic solvent which was then diluted with water to give a 5% (v/v) content. The pesticides were isolated with fused silica fiber coating with 85 μm polyacrylate. Parameters that affect both the extraction of the fungicides by the soil samples and the trapping of the analytes by the fiber were investigated and their impact on the SPME-GC-MS was studied. The procedures with respect to repeatability and limits of detection were evaluated by soil spiked with both analytes. Repeatability was between 5.6 and 14.2% and the limits of detection were 2-13 ng g⁻¹. The efficiency of acetone/SPME was generally better than that for water/SPME procedure showing good linearity (R²>0.99) with coefficient variations below 9%, recoveries higher than 91% and limits of detection between 2 and 3 ng g⁻¹. Finally, the recoveries obtained with acetone/SPME procedure were compared with the conventional liquid-liquid extraction using real soil samples. The acetone/SPME method was shown to be an inexpensive, fast and simple preparation method for the determination of target analytes at low nanogram per gram levels in soils.     

Development and validation of a solid-phase microextraction method for the analysis of volatile organic compounds in groundwater samples

Summary Solid-phase microextraction is a relatively recent extraction technique for sample preparation. It has been used successfully to analyse environmental pollutants in a variety of matrices such as soils, water and air. In this work, a simple and rapid method for the analysis of volatile organic and polar compounds from polluted groundwater samples by SPME coupled with gas chromatography (GC) is described. Different types of fibres were studied and the extraction process was optimised. The fibre that proved to be the best to analyse this kind of samples was CAR-PDMS. The method was validated by analysis of synthetic samples and comparison with headspace—GC. The optimised method was successfully applied to the analysis of ground-water samples.     

Solid phase microextraction of volatile organic compounds using carboxen-polydimethylsiloxane fibers

Summary A new 80 μm Carboxen-polydimethylsiloxane (PDMS) fiber for solid phase microextraction (SPME) was tested for the enrichment of volatile organic compounds from water and air. Detection limits between 13 ng L⁻¹ (CH₂Cl₂) and 0.1 ng L⁻¹ (CHCl₂Br and CHClBr₂) for the combination: Carboxen-PDMS fiber and GC-ECD and between 35 ng L⁻¹ and 45 ng L⁻¹ (BTEX compounds) for the combination: Carboxen-PDMS and GC-FID using the headspace procedure were determined. Comparisons with the 100 μm PDMS fiber and further coatings show the advantages of the Carboxen-PDMS fiber with respect to extraction efficiency. Disadvantages of the new fiber compared with the 100 μm PDMS fiber are poorer repeatability and prolongation of equilibrium time. Distribution coefficients of the BTEX compounds between aqueous solution and SPME fiber coating were calculated and compared with the results of other researchers and with octanol-water partition coefficients.     

Improved method to quantitatively determine powerful odorant volatile thiols in wine by headspace solid-phase microextraction after derivatization

A solid-phase microextraction (SMPE) method coupled to a gas chromatography–mass spectrometry analysis was optimized to analyze the pentafluorobenzyl bromide (PFBBr) derivatives of the volatile thiols 4-methyl-4-mercapto-2-pentanone (4MMP), 3-mercaptohexyl acetate (3MHA) and 3-mercaptohexanol (3MH) in wine. This method used deuterated analogue compounds as internal standards. It allowed us to significantly reduce the matrix effect, resulted in good repeatability for all the compounds (RDS < 9.5% for 4MMP; <6% for 3MH and <4.1% for 3MHA) with limits of detection below their odour thresholds. The method was validated using white, rosé and red wines. When applied to analyze different wines, quantities closed to the odour threshold were determined.     

Sampling and sample-preparation strategies based on solid-phase microextraction for analysis of indoor air

Applications of solid-phase microextraction (SPME) to the sampling and analysis of volatile organic compounds in indoor air are reviewed, including a summary of quantification methods, coatings, compounds, concentrations, sampling locations and times, and detection limits. Strategies for on-site and off-site sampling and analysis, advantages and challenges associated with SPME for air sampling are discussed.     

Determination of chloro-s-triazines including didealkylatrazine using solid-phase extraction coupled with gas chromatography-mass spectrometry

Chloro-s-triazines are a class of compounds comprising atrazine, simazine, propazine, cyanazine and their chlorinated metabolites. The US Environmental Protection Agency (EPA) has determined that selected chloro-s-triazines--atrazine, simazine, propazine, deethylatrazine, deisopropylatrazine, and didealkylatrazine--have a common mode of toxicity related to endocrine disruption. In this paper, a dual-resin solid-phase extraction (SPE) gas chromatography-mass spectrometry (GC-MS) method is reported that provides for each of these chloro-s-triazines including the polar metabolite, didealkylatrazine. The method utilizes deuterated internal standards for quantitation and terbuthylazine as a recovery standard. The limit-of-detection was 0.01 microg/L for simazine, deethylatrazine, deisopropylatrazine and didealkylatrazine, and 0.02 microg/L for atrazine and propazine in surface water. Mean recoveries for 0.5 and 3.0 microg/L spikes for atrazine, simazine, propazine, deethylatrazine, deisopropylatrazine and didealkylatrazine were 94, 104, 103, 110, 108 and 102%, respectively, in surface water. The method was also validated by matrix spikes into fourteen different raw and treated natural surface waters. This method is useful for monitoring "total chloro-s-triazines" in both raw and treated drinking waters.     

Analysis of odorous trichlorobromophenols in water by in-sample derivatization/solid-phase microextraction GC/MS

The simultaneous determination of several odorous trichlorobromophenols in water has been carried out by an in-sample derivatization headspace solid-phase microextraction method (HS-SPME).The analytical procedure involved their derivatization to methyl ethers with dimethyl sulfate/NaOH and further HS-SPME and gas chromatography-mass spectrometry (GC/MS) determination. Parameters affecting both the derivatization efficiency and headspace SPME procedures, such as the selection of the SPME fiber coating, derivatization–extraction time and temperature, were studied. The commercially available polydimethylsiloxane (PDMS) 100 μm and Carboxen-polydimethylsiloxane-divinylbenzene (CAR-PDMS-DVB) fibers appeared to be the most suitable for the simultaneous determination of these compounds. The precision of the HS-SPME/GC/MS method gave good relative standard deviations (RSDs) run-to-run between 9% and 19% for most of them, except for 2,5-diCl-6-Br-phenol, 2,6-diCl-3-Br-phenol and-2,3,6-triBr-phenol (22%, 25% and 23%, respectively). The method was linear over two orders of magnitude, and detection limits were compound dependent but ranged from 0.22 ng/l to 0.95 ng/l. The results obtained for water samples using the proposed SPME procedure were compared with those found with the EPA 625 method, and good agreement was achieved. Therefore, the in-sample derivatization HS-SPME/GC/MS procedure here proposed is a suitable method for the simultaneous determination of odorous trichlorobromophenols in water.     

固相萃取-衍生化气相色谱/质谱法测定制药厂污水中的环境雌激素

采用固相萃取-衍生化气相色谱/质谱法(GC/MS)测定某制药厂污水中的雌酮(E1)、雌二醇(E2)、雌三醇(E3)和乙炔基雌二醇(EE2)4种雌激素化合物。样品经固相萃取柱萃取富集及双(三甲基硅烷基)三氟乙酰胺(1%三甲基氯硅烷)（BSTFA(1%TMCS)）衍生化后进行GC/MS分析。该法对4种目标物的检出限为1.8～4.7 ng/L,相对标准偏差为2.3%～9.1%(n=8)。目标化合物的加标回收率为（94.0±2.9）%～（101±3.8）%,说明该方法能较好地应用于污水中雌激素化合物的定量检测。通过对某制药厂污水中的雌激素进行定量分析,发现污水中乙炔基雌二醇和雌酮质量浓度分别达396.6 和39.9 ng/L;经过传统的厌氧兼氧好氧生物处理后,污水中的环境雌激素的去除率仅为35%～40%,说明传统的污水处理工艺对去除污水中雌激素效果并不明显,需要改进。     

Comparison of simultaneous distillation extraction and solid-phase microextraction for the determination of volatile flavor components

Traditional simultaneous distillation extraction (SDE) and solid-phase microextraction (SPME) techniques were compared for their effectiveness in the extraction of volatile flavor compounds from various mustard paste samples. Each method was used to evaluate the responses of some analytes from real samples and calibration standards in order to provide sensitivity comparisons between the two techniques. Experimental results showed traditional SDE lacked the sensitivity needed to evaluate certain flavor volatiles, such as 1,2-propanediol. Dramatic improvements in the extraction ability of the SPME fibers over the traditional SDE method were noted. Different SPME fibers were investigated to determine the selectivity of the various fibers to the different flavor compounds present in the mustard paste samples. Parameters that might affect the SPME, such as the duration of absorption and desorption, temperature of extraction, and the polarity and structure of the fiber were investigated. Of the various fibers investigated, the PDMS–DVB fiber proved to be the most desirable for these analytes.     

固相微萃取技术分析纺织品中全氟化合物

采用二甲基十八烷基[3-三甲氧基硅丙基]氯化铵与纤维素基底表面的羟基发生硅烷化反应,制备出带有季铵盐(R_4N^+)正离子的新型固相微萃取涂层,采用扫描电子显微镜(SEM)和红外光谱(IR)表征涂层结构。将新型涂层用于纺织品中全氟化合物(OEKO-TEX Standard100中规定的9种)的分析,优化了影响涂层萃取效率的各个因素,建立了固相微萃取-液相二级质谱联用测试9种全氟化合物的方法。实验结果表明,方法线性相关系数R^2≥0. 9907,对于同一SPME萃取针精密度相对标准偏差(RSD)在4. 1%～9. 2%,不同萃取针精密度RSD在2. 6%～7. 9%,平均加标回收率为96. 3%～105. 9%,回收率相对标准偏差为2. 8%～11%。     

Detection of volatile organic compounds indicative of human presence in the air

Volatile organic compounds were collected and analyzed from a variety of indoor and outdoor air samples to test whether human‐derived compounds can be readily detected in the air and if they can be associated with human occupancy or presence. Compounds were captured with thermal desorption tubes and then analyzed by gas chromatography with mass spectrometry. Isoprene, a major volatile organic compound in exhaled breath, was shown to be the best indicator of human presence. Acetone, another major breath‐borne compound, was higher in unoccupied or minimally occupied areas than in human‐occupied areas, indicating that its majority may be derived from exogenous sources. The association of endogenous skin‐derived compounds with human occupancy was not significant. In contrast, numerous compounds that are found in foods and consumer products were detected at elevated levels in the occupied areas. Our results revealed that isoprene and many exogenous volatile organic compounds consumed by humans are emitted at levels sufficient for detection in the air, which may be indicative of human presence.     

Fast determination of VOCs in workplace air by solid-phase extraction and gas chromatography-mass spectrometry

Summary A fast, simple, and reliable method is presented for the determination of atmospheric semi-volatile organic pollutants at μg m⁻³ levels. The method has been used to monitor potentially carcinogenic toxic compounds to which workers are exposed in workplaces, and to measure the same compounds in outdoor air. Dedicated to Michele Di Pasquale (deceased).     

Analysis of volatile organic compounds in pleural effusions by headspace solid‐phase microextraction coupled with cryotrap gas chromatography and mass spectrometry

Headspace solid‐phase microextraction coupled with cryotrap gas chromatography and mass spectrometry was applied to the analysis of volatile organic compounds in pleural effusions. The highly volatile organic compounds were separated successfully with high sensitivity by the employment of a cryotrap device, with the construction of a cold column head by freezing a segment of metal capillary with liquid nitrogen. A total of 76 volatile organic compounds were identified in 50 pleural effusion samples (20 malignant effusions and 30 benign effusions). Among them, 34 more volatile organic compounds were detected with the retention time less than 8 min, by comparing with the normal headspace solid‐phase microextraction coupled with gas chromatography and mass spectrometry method. Furthermore, 24 volatile organic compounds with high occurrence frequency in pleural effusion samples, 18 of which with the retention time less than 8 min, were selected for the comparative analysis. The results of average peak area comparison and box‐plot analysis showed that except for cyclohexanone, 2‐ethyl‐1‐hexanol, and tetramethylbenzene, which have been reported as potential cancer biomarkers, cyclohexanol, dichloromethane, ethyl acetate, n‐heptane, ethylbenzene, and xylene also had differential expression between malignant and benign effusions. Therefore, the proposed approach was valuable for the comprehensive characterization of volatile organic compounds in pleural effusions.     

Determination of the volatile constituents of ChineseCoriandrum sativum L. by gas chromatography—Mass spectrometry with solid-phase microextraction

Summary Fifteen main volatile compounds in ChineseCoriandrum sativum L. were separated and identified by gas chromatography—mass spectrometry (GC-MS) combined with solid-phase microextraction (SPME). Fresh ChineseCoriandrum sativum L. was ground and its volatile compounds were extracted by SPME with a 100 μm polydimethylsiloxane fiber. The fibers were desorbed in a GC injection liner at 250°C for 3 min. More than 15 peaks were separated by headspace SPME-GC-MS analysis. The main compounds in headspace ofCoriandrum sativum L. identified by mass spectrometry included decanal, 2-decenal, 1-decanol,trans-2-decen-1-ol,trans-2-decen-1-al,trans-2-tridecenal etc, which were verified by reference compounds. Their relative contents were calculated on basis of peak areas. SPME extraction conditions and capillary chromatography column used to separate the volatile compounds were investigated.     

Static headspace versus head space solid-phase microextraction (HS-SPME) for the determination of volatile organochlorine compounds in landfill leachates by gas chromatography

The determination of five volatile organochlorine compounds, VOX (chloroform, 1,1,1-trichloroethane, carbon tetrachloride, trichloroethene and tetrachloroethene) in raw landfill leachates and biologically cleansed leachates by GC-MS is investigated. Two extraction and preconcentration procedures were evaluated for recovery of such analies from the samples, including static headspace (HS) and solid phase microextraction by sampling the headspace above the sample (HS-SPME). Optimisation of operating parameters for the best performance of both, sampling and preconcentration techniques was described. Detection limits, time of analysis, precision and linear ranges of both introduction techniques have been established. Application of proposed methods to the determination of the five VOX under study in the above referred samples revealed the absence of such analytes in both leachates. Then both methods were applied to the determination to the five organochlorine compounds under study on spiked leachates samples. While HS-GC-MS offered better analytical precision than HS-SPME-GC-MS, this last technique gave a faster analytical response because no dilution must be done for a reliable VOX determination in landfill leachates. In any case, both sample introduction techniques tested provides excellent recoveries and good analytical precision (ranged from 1 to 3%).     

High extraction efficiency for polar aromatic compounds in natural water samples using multiwalled carbon nanotubes/Nafion solid-phase microextraction coating

A novel solid-phase microextraction (SPME) fiber coated with multiwalled carbon nanotubes (MWCNTs)/Nafion was developed and applied for the extraction of polar aromatic compounds (PACs) in natural water samples. The characteristics and the application of this fiber were investigated. Electron microscope photographs indicated that the MWCNTs/Nafion coating with average thickness of 12.5 μm was homogeneous and porous. The MWCNTs/Nafion coated fiber exhibited higher extraction efficiency towards polar aromatic compounds compared to an 85 μm commercial PA fiber. SPME experimental conditions, such as fiber coating, extraction time, stirring rate, desorption temperature and desorption time, were optimized in order to improve the extraction efficiency. The calibration curves were linear from 0.01 to 10 μg mL⁻¹ for five PACs studied except p-nitroaniline (from 0.005 to 10 μg mL⁻¹) and m-cresol (from 0.001 to 10 μg mL⁻¹), and detection limits were within the range of 0.03–0.57 ng mL⁻¹. Single fiber and fiber-to-fiber reproducibility were less than 7.5 (n = 7) and 10.0% (n = 5), respectively. The recovery of the PACs spiked in natural water samples at 1 μg mL⁻¹ ranged from 83.3 to 106.0%.