High-performance polyethylene glycol-coated solid-phase microextraction fibers using sol-gel technology

The sol-gel method is applied for the preparation of solid-phase microextraction (SPME) fibers. An electron microscopy experiment suggested a porous structure for Superox-4 (polyethylene glycol, PEG) coating. SPME-GC analyses provided evidence that the sol-gel fibers have some advantages, such as high velocities of mass transfer, efficient extraction rates. high thermal stability, long life span, and spacious range of application for both polar and non-polar analytes. Efficient SPME-GC analyses of benzene-toluene-ethylbenzene-xylenes, phenols, phthalic diesters, naphthalene congeners and pesticides were achieved using sol-gel-coated PEG fibers.     

基于基质修饰的多次顶空固相微萃取-气相色谱法检测酒精饮料中的氨基甲酸乙酯

氨基甲酸乙酯(EC)是发酵食品在发酵或贮存过程中产生的致癌副产物。建立了多次顶空固相微萃取-气相色谱法(MHS-SPME-GC)检测多种酒精饮料中EC的方法。采用自制的溶胶-凝胶聚乙二醇/羟基硅油复合SPME萃取头提高了方法的灵敏度,加入无水硫酸钠对基质进行修饰大大提高了EC的萃取效率。在优化条件下,方法的线性范围为0.04～100 mg/L,线性相关系数为0.9997,检出限为34 μg/L;方法重现性好,6次重复实验所得相对标准偏差为2.19%;准确度高,加标回收率在90.9%～103.6%之间。将建立的方法用于多种实际酒样中EC的检测,其结果与标准加入法得到的结果在统计学上无显著差异。本研究表明,MHS-SPME能够克服通常存在于SPME分析中的基质干扰效应,尤其适合于大量不同基质的样品分析。     

Headspace solid-phase microextraction applied to the simultaneous determination of sorbic and benzoic acids in beverages

A new analytical procedure was developed using headspace solid-phase microextraction (HS-SPME) for the simultaneous determination of sorbic and benzoic acids in beverages. The sample were processed depending on their nature, either only diluted with water, or treated with a NaOH solution and filtered through a 0.45-μm membrane filter. The samples were heated in a vial in the presence of sulfuric acid and anhydrous sodium sulfate and the analytes were collected from the headspace by using a 65-μm polydimethylsiloxane-divinylbenzene (PDMS-DVB) coated fiber and determined by gas chromatography with flame ionization detector (GC-FID). To enhance the sensitivity of HS-SPME, the temperature and time of the extraction and desorption, the acidity and salt concentration of the extraction solution were optimized. Linear range of the analytes was found to be between 0.1 and 20 mg/L with regression coefficients (R²) of 0.9998 for sorbic acid and 0.9980 for benzoic acid. Limits of detection (LOD) were 5.83 μg/L and 11.4 μg/L for sorbic and benzoic acids, respectively. Relative standard deviation (R.S.D.) for six replicate analyses within 3 days (two times/day) was found to be lower than 8.62% at three concentration levels (2, 6, 10 mg/L). Recoveries ranged from 81.20% to 108.1% for real samples. The results demonstrate the suitability of the HS-SPME technique to analyze sorbic and benzoic acids in a variety of beverages.     

纳米SiO2膜新型萃取头固相微萃取测定蔬菜中5种农药残留量的研究

建立了以纳米SiO2膜为萃取头涂层的固相微萃取(SPME)-气相色谱(GC)联用测定蔬菜中5种农药残留 (p,p′-DDD, p,p′-DDE, o,p′-DDT, p,p′-DDT, 联苯菊酯)的新方法. 探讨并优化了萃取时间、萃取温度和转子转速等参数.     

Preparation and investigation of polymethylphenylvinylsiloxane-coated solid-phase microextraction fibers using sol-gel technology

Summary Poly(methylphenylvinylsiloxane) (PMPVS) coating was first prepared using sol-gel technology and applied for solid-phase microextraction (SPME). The extraction properties of the novel coating for volatile and semi-volatile organic compounds were investigated using a homemade SPME device coupled with GC-FID. The porous surface structure of the coating provided high surface area and allowed for high extraction efficiency. Compared with commercial SPME stationary phase, the new phase showed better selectivity and sensitivity toward the various analytes, due to their inherent multifunctional properties and the features of sol-gel chemistry. Furthermore, PMPVS coating showed good thermal stability and long lifetime.     

Gas chromatographic determination of formaldehyde in air using solid-phase microextraction sampling

Summary The optimization of in situ derivatization and preconcentration of formaldehyde in air using solid phase microextraction with gas chromatographic determination was investigated. A dimethylpolysiloxane coating (7 μm) solid-phase microextraction needle was used in the final procedure as a support for derivatizing reagents such as 2,4-dinitrophenylhydrazine and acetylacetone. Standard concentrations of formaldehyde in air were obtained using a headspace technique and equilibrium concentrations of formaldehyde in air were calculated using Henry's law. After derivatization on the fiber, the derivative was thermally desorbed in the injector of a gas chromatograph and analyzed using an electron capture detector. A detection limit of 0.17 mg m⁻³ was obtained. Calibration was done at 296 K. Reproducibility of the method was 9.6%. Some real air samples were also analyzed. The method is very convenient and ideal for the rapid determination of formaldehyde in air. Presented at: Balaton Symposium on High-Performance Separation Methods, Siófok, Hungary, September 3–5, 1997     

介孔涂层固相微萃取-高效液相色谱法测定水样中邻苯二羧酸酯化合物

以苯基官能化MCM-41介孔复合体作为固相微萃取(SPME)的吸附涂层, 与高效液相色谱(HPLC)联用测定了不同水样中邻苯二甲酸二甲酯(DMP)、邻苯二甲酸二乙酯(DEP)、邻苯二甲酸二丁酯(DBP)和邻苯二甲酸二辛酯(DOP)的含量, 对SPME的吸附和解吸时间、温度、搅拌速度进行了优化, 线性范围分别为1.19×10-4～119 μg/L、 1.12×10-4～112 μg/L、 1.05×10-4～105 μg/L和9.80×10-5～98 μg/L, 检出限依次为0.030、 0.027、 0.029和0.022 ng/L. 使用该方法测定了多种水样中邻苯二羧酸酯类化合物.     

Multi-residual GC-MS determination of personal care products in waters using solid-phase microextraction

A multi-residual method is described for the simultaneous determination of 23 personal care products (PCPs), which display a wide range of physicochemical properties, present at trace levels in water samples. A one-step procedure was developed based on solid-phase microextraction (SPME) coupled with GC-MS analysis. A chemometric approach consisting of an experimental design (design of experiments) was applied to systematically investigate how four operating parameters—extraction temperature and time and desorption temperature and time—affect extraction recovery of PCPs in water. The optimum SPME procedure operating conditions, those yielding the highest extraction recovery for all the compounds, were determined; they correspond to an extraction time of 90 min and temperature of 80 °C and a desorption time of 11 min and temperature of 260 °C. Under these optimized conditions, the SPME procedure shows good analytical performance characterized by high reproducibility (RSD% intra-day accuracy varying in the 0.01–1.3% range) as well as good linearity and low detection limits (LODs lower than 2 ppb for most of the investigated PCPs).     

Factors affecting multiresidue determination of priority herbicides when using solid-phase microextraction

A solid-phase microextraction (SPME) procedure was developed for the determination of 10 selected organonitrogen herbicides (s-ethyl dibropylthiocarbamate [EPTC], molinate, propachlor, trifluralin, simazine, atrazine, propazine, terbuthylazine, alachlor, and prometryn) and was tested with various natural waters. Gas chromatography coupled with flame thermionic and mass spectrometric detection was used for quantitation. For this purpose, polydimethylsiloxane and polyacrylate fibers were used and the factors affecting the SPME process such as pH, ionic strength, methanol content, memory effect, stirring rate, and adsorption-time profile were investigated and optimized. By using spiked liquid chromatography water, optimal factors were determined to be 25% salt, <0.5% methanol, stirring rate of 960 rpm, pH 4, and an equilibrium time of 30 min. These conditions were used in further studies of the fibers and in analysis of natural water samples. The method was applied to spiked natural waters such as ground water, sea water, lake water, and river water at a concentration range of 0.5-10 microg/L. Limits of detection ranged from 5 to 90 ng/L, and precision ranged from 5 to 15% (as relative standard deviation), depending on the pesticide, fiber, and detector used. The recoveries of herbicides were 70.2-118.4%, and the average r2 values of the calibration curves were >0.99 for all analytes. The results demonstrate the suitability of the SPME method to determine these organonitrogen herbicides in various natural waters. River water samples originating from the Epirus region (Northwestern Greece) were analyzed to verify the performance of the optimized method by comparing the results obtained by SPME with those obtained by using conventional solid-phase extraction of the selected herbicides.     

Development of a solid-phase microextraction method with micellar desorption for the determination of chlorophenols in water samples. Comparison with conventional solid-phase microextraction method

A novel analytical method is presented for the determination of chlorophenols in water. This method involves pre-concentration by solid-phase microextraction (SPME) and an external desorption using a micellar medium as desorbing agent. Final analysis of the selected chlorophenols compounds was carried out by high-performance liquid chromatography (HPLC) with diode array detection (DAD). Optimum conditions for desorption, using the non-ionic surfactant polyoxyethylene 10 lauryl ether (POLE), such as surfactant concentration and time were studied. A satisfactory reproducibility for the extraction of target compounds, between 6 and 15%, was obtained, and detection limits were in the range of 1.1-5.9ngmL(-1). The developed method is evaluated and compared with the conventional one using organic solvent as a desorbing agent. The method was successfully applied to the determination of chlorophenols in water samples from different origin. This study has demonstrated that solid-phase microextraction with micellar desorption (SPME-MD) can be used as an alternative to conventional SPME method for the extraction of chlorophenols in water samples.     

Solid-phase microextraction of phenol compounds using a fused-silica fiber coated with beta-cyclodextrin-bonded silica particles.

A novel solid-phase microextraction (SPME) fiber was prepared by coating an HPLC beta-cyclodextrin bonded silica stationary phase (CDS) on the surface of a fused-silica fiber. The fiber was evaluated for the determination of five phenol compounds (phenol, 2,4-dimethylphenol, 4-nitrophenol, 3-chlorophenol, 4-methylphenol). Compared with commercially available polymer coatings, the CDS coating showed high sensitivity and fast velocity of mass transfer for phenol compounds because of its porous structure and a unique molecular structure of beta-cyclodextrin. In addition, the CDS coating was proved to be very stable at a relatively high temperature (up to 300 degrees C). The method was suitable for the determination of phenol compounds in aqueous samples. The determination of 4-nitrophenol in soil by microwave-assisted extraction (MAE) coupled to solid-phase microextraction was also investigated.     

Quantifying sesquiterpene and oxygenated terpene emissions from live vegetation using solid-phase microextraction fibers

Biogenic terpenes play important roles in ecosystem functioning and atmospheric chemistry. Some of these compounds are semi-volatile and highly reactive, such as sesquiterpenes and oxygenated terpenes, and are thus difficult to quantify using traditional air sampling and analysis methods. We developed an alternative approach to quantify emissions from live branches using a flow through enclosure and sample collection on solid-phase microextraction (SPME) fibers. This method allows for collection and analysis of analytes with minimal sample transfer through tubing to reduce the potential for losses. We characterized performance characteristics for 65 microm polydimethylsiloxane-divinylbenzene (PDMS/DVB) fibers using gas chromatography followed by mass spectrometry and optimized experimental conditions and procedures for field collections followed by laboratory analysis. Using 10-45 min sampling times and linear calibration curves created from mixtures of terpenes, emissions of methyl chavicol, an oxygenated terpene, and an array of sesquiterpenes were quantified from a Ponderosa pine branch. The detection limit was 4.36 pmol/mol (ppt) for methyl chavicol and 16.6 ppt for beta-caryophyllene. Concentrations determined with SPME fibers agreed with measurements made using proton transfer reaction mass spectrometry (PTR-MS) within the estimated error of the method for well calibrated compounds. This technique can be applied for quantification of biogenic oxygenated terpene and sesquiterpene emissions from live branches in the field.     

管内硼亲和固相微萃取-高效液相色谱全自动在线联用检测茶饮料中的顺式二羟基化合物

自动化联用分析技术对于降低人力强度、提高效率和保证数据重现性等具有重要意义。硼亲和固相微萃取(BA-SPME)是近十年出现的用于富集顺式二羟基化合物的独特工具,但BA-SPME与高效液相色谱(HPLC)的自动化在线联用还未见报道。该文报道了一种新颖的管内BA-SPME-HPLC全自动在线联用方法,用于分析茶饮料中的顺式二羟基化合物。该自动化在线联用方法利用自动进样器通过六通阀的切换实现流路连接。制备了管内BA-SPME毛细管,考察了涂层柱的柱容量,并对其形貌进行了表征,考察并优化了影响实际样品分离效果的因素。最后,利用该联用方法对3种不同品牌的茶饮料进行了分析,并对沏茶温度对茶水中顺式二羟基化合物含量的影响进行了评价。     

Estimation of measurement uncertainty for the determination of nonylphenol in water using solid-phase extraction and solid-phase microextraction procedures

We describe an estimation of measurement uncertainty calculated by the “bottom-up” approach for the determination of the oestrogenic compound nonylphenol in treated water samples by solid-phase extraction (SPE) and solid-phase microextraction (SPME) procedures and GC/MS detection. The results were compared and the different contributions to the uncertainty were evaluated. A study of the linear range was established and validation was performed for both methods using statistical analysis of several indicative parameters. In terms of validation data, precision (R.S.D. values <20%) and trueness (relative error <11%) were obtained for both methods under day-to-day conditions. The results of the estimation of measurement uncertainty obtained for both methods for concentrations higher than 1 μg/l have demonstrated that the time-consuming SPE method has a lower relative uncertainty (32%) than the SPME method (42.8%). The chromatographic uncertainty value was the main factor in the SPME method whereas the recovery factor (used to calculate the concentration) was the main contribution to uncertainty in the SPE method.     

Headspace solid-phase microextraction of sulphides and disulphides using Carboxen-polydimethylsiloxane fibers in the analysis of wine aroma

Headspace solid-phase microextraction was applied to gas chromatography coupled to flame photometric detection to develop a method for analysing volatile sulphides and disulphides in wine. The Carboxen-polydimethylsiloxane-coated silica fiber was tested and different parameters such as presampling time, ionic strength, stirring, headspace volume, ethanol concentration, time and temperature of extraction were optimized to make extraction as efficient as possible. The optimized conditions enabled limits of detection to be obtained at the ng/l levels. The fiber tested has a strong affinity for the sulphur compounds studied and enables these analytes to be quantitatively determined in wines. The Carboxen-polydimethylsiloxane-coated fiber is more efficient at extracting than fibers such as those which are polydimethylsiloxane-coated and polyacrylate-coated, but its repeatability is worse. The overall process was successfully applied to identify and quantify sulphur compounds in white, red, rose and vintage wines.     

以铅笔芯为吸附基质的顶空-固相微萃取法测定酒中的甲醇

固相微萃取(SPME)是以固相萃取(SPE)为基础发展起来的新方法。在多次实验后发现,主要成分为碳的铅笔芯在经过一定的物理,化学处理后对被分析物能产生定量吸附,因此可用作SPME的萃取基质。对该吸附基质,选择了其萃取、解吸的最佳条件如:萃取时间,水浴温度,搅拌速度,解吸时间及温度等。在选定的最佳条件下,以铅笔芯作吸附基质对甲醇进行顶空 固相微萃取测定,其线性范围是5×10-6～2×10-7g/mL,线性相关系数r=0.9975。富集20min后,检出限为0.5×10-7g/mL。使用该法测定了5种酒中的甲醇含量,回收率在95%～110%之间。在对同一样品的3次平行测定中,其相对标准偏差在6%以下。     

Development of new solid-phase microextraction fibers by sol-gel technology for the determination of organophosphorus pesticide multiresidues in food

Allyloxy bisbenzo 16-crown-5 trimethoxysilane was first used as precursor to prepare the sol-gel-derived bisbenzo crown ether/hydroxyl-terminated silicone oil (OH-TSO) SPME coating. The coating procedure involving sol solution composition and conditioning process was presented. Compared with commercial SPME stationary phases, the new coatings showed higher extraction efficiency and therefore could provide higher sensitivity for organphosphorous pesticides (OPs). Limits of detection (LODs) were in the range of 0.003-1.0 ng/g for these OPs in food samples (honey, juice, orange and pakchoi). The optimal extraction conditions of the new coatings to OPs in these samples were investigated by adjusting extraction time, salt addition, extraction temperature, and dilution ratios of samples with distilled water by using SPME coupled with gas chromatography (GC)-flame photometric detection (FPD). The method was applied to determine the concentrations of OPs in real samples.     

Single-walled carbon nanotubes coated fibers for solid-phase microextraction and gas chromatography-mass spectrometric determination of pesticides in Tea samples

Using a single-walled carbon nanotubes (SWCNTs) as stationary phase of solid-phase microextraction (SPME) fibers, a simple, low cost and environmentally friendly method for extraction of 13 pesticides in Tea samples has been developed following gas chromatography-mass spectrometric determination. Potential factors affecting the extraction efficiency were investigated and optimized, including extraction and desorption time, extraction temperature, stirring rate, solution pH and ionic strength. Under optimized conditions, the linearity of the developed method was in the range of 0.125-25 ng/mL with correlation coefficients greater than 0.9928 and the limits of detections (LODs) were 0.027-0.23 ng/mL (S/N = 3). Meanwhile, the relative standard deviations (RSDs) for five successive measurements with single fiber, fiber-to-fiber, day-to-day were 2.3-13.0, 8.2-14.6 and 4.1-12.5%, respectively, indicating good reproducibility of the proposed method. The fiber had high extraction efficiency for studied pesticides in comparison with commercial poly(dimethylsiloxane) (PDMS) and polyacrylate (PA) fibers and could be used for more than 70 times without decrease of efficiency. The developed method was successfully applied for the analysis of real samples including green Tea, oolong Tea, white Tea, and flower Tea, and the recoveries of the pesticides spiked in these samples ranged from 75.1 to 118.4%. Chlorfenapyr and λ-cyhalothrin were found in the Tea samples bought randomly from local market. The results demonstrated that the developed SWCNTs-SPME method was a simple, efficient pretreatment and enrichment procedure for pesticides in complex matrices.     

Potential of solid-phase microextraction fibers for the analysis of volatile organic compounds in air.

This work presents the usefulness of five different solid-phase microextraction fibers in the screening of volatile organic compound (VOC) traces in air samples. The performances of these fibers are compared by studying the sorption kinetics in an equimolar gaseous mixture of eleven VOCs. For each fiber, static and dynamic sampling are compared. It is shown that repeatability is better for the dynamic mode (less than 6% for dynamic sampling and 10% for static sampling). The equilibrium time and the sensitivity vary considerably from one fiber type to another. As an example, the classical polydimethylsiloxane (PDMS) coating presented the shortest equilibration time (5 min) but also the poorest sensitivity, whereas the PDMS-Carboxen showed the longest extraction time but the greatest sensitivity. The estimation of the quantity of VOCs fixed on the target fiber allows for the determination of the different affinities of the compounds with the involved sorbent and relates them with physicochemical properties of the molecules. Competitive sorption is observed for the fibers involved with the adsorption process (i.e., PDMS-divinylbenzene and PDMS-Carboxen fibers). These competitions can lead to SPME calibration problems and thus bad quantitative analysis.