Solid-phase microextraction in pesticide residue analysis

The applications of solid-phase microextraction (SPME) for sample preparation in pesticide residue analysis are reviewed in this paper taking into account the different approaches of this technique coupled mainly to gas chromatography but also to high-performance liquid chromatography. A complete revision of the existing literature has been made considering the different applications divided according to the pesticide families (organochlorine, organophosphorus, triazines, thiocarbamates, substituted uracils, urea derivatives and dinitroanilines among others) and the sample matrices analysed which included environmental samples (water and soil), food samples and biological fluids. Details on the analytical characteristics of the procedures described in the reviewed papers are given, and new trends in the applications of SPME in this field are discussed.     

Solid-phase microextraction of N-nitrosamines

A method was developed for the extraction of seven N-nitrosamine compounds from water by solid-phase microextraction (SPME). The method developed requires a total analysis time of only 1.25 h for both extraction and detection (versus 3-20 h for other isolation techniques). Three gas chromatography (GC) detection systems were tested with the SPME method, nitrogen chemiluminesence detection (NCD), nitrogen-phosphorus detection (NPD) and chemical ionization mass spectrometry (CI-MS), with method detection limits (MDLs) found in the ng/L range. This method was used to analyze wastewater samples and showed excellent selectivity of extraction. The detection limits of this method for N-nitrosodimethylamine (NDMA) range from 30 to 890 ng/L as a function of detector type. The excellent selectivity of SPME in addition to the fast analysis time would make this method ideal for general surveys, wastewater analysis and laboratory studies (e.g. degradation kinetics or formation potential).     

Solid-phase microextraction in the analysis of food taints and off-flavors

Selected food taints and off flavors, for which solid phase microextraction (SPME) has been used as a method for volatiles isolation, are the subject of review. Compounds responsible for musty and earthy odor off-flavors and taints in foods are discussed. This group contains haloanisoles, geosmin, and methylisoborneol. Chlorophenols are discussed as precursors of chloroanisoles and compounds impairing the flavor of food. Also described are volatile phenolic compounds responsible for medicinal off flavors, mainly ethyl phenols and vinyl phenols. Sulfur compounds that contribute to off-flavor are also discussed. Finally, a group of volatile compounds being the products of lipid oxidation are summarized. A short review of the formation, occurrence, and information on odor properties of all of these groups of compounds is given. Examples of SPME use for the analysis of compounds belonging to all described groups are shown. Elaboration of method parameters, fiber selection, experimental conditions, and quantitation of compounds are subjects of interest. Also, applications of SPME as a method for introduction of volatiles in mechanical olfaction technologies are shortly outlined.     

Solid-phase microextraction for the enantiomeric analysis of flavors in beverages

Solid-phase microextraction combined with gas chromatographic/mass spectrometric analysis and separation on a chiral cyclodextrin stationary phase was a rapid, reliable technique for profiling chiral aroma compounds in flavored alcoholic beverages. Several enantiomeric terpenes, esters, alcohols, norisoprenoids, and lactones were identified in berry-, peach-, strawberry-, and citrus-flavored wine and malt beverages (wine coolers). Using this technique, we were able to confirm the addition of synthetic flavoring to several beverages, consistent with label designations.     

Solid-phase microextraction versus single-drop microextraction for the analysis of nitroaromatic explosives in water samples.

This paper compares solid-phase microextraction (SPME) with a recently developed extraction method called single-drop microextraction (SDME) for the analysis of nitroaromatic explosives in water samples. The two techniques are examined in terms of procedure, chromatographic analysis and method performance. All practical considerations for both techniques are also reviewed. SPME requires dedicated apparatus and is relatively expensive, as the fiber's lifetime is limited. However, it has the advantages over SDME that it can be easily used for headspace analysis and has lower detection limits for all the target analytes. SDME requires more elaborate manual operations, thus affecting linearity and precision.     

Solid-phase microextraction method for the quantitative analysis of styrene in water

A headspace solid-phase microextraction (HS-SPME) method is developed for the determination of styrene in drinking water. Gas chromatography (GC)-mass spectrometry is utilized for qualitative analysis. A manual SPME holder with 85-microm polyacrylate coating is used to extract the styrene from water, which is determined to have good linearity (correlation coefficient r = 0.9999 for 1.00-100.00 microg/L range), a relative standard deviation of 1.9%, and a detection limit of 0.30 microg/L. This method is compared with a classical headspace GC method.     

Solid-phase microextraction of polychlorinated biphenyls

The extraction and analysis of 21 polychlorinated biphenyls (PCBs) ranging from di- to decachlorobiphenyls in ocean, wetland and leachate water samples were achieved using solid-phase microextraction (SPME) with a 100-μm poly(dimethylsiloxane) (PDMS) fiber and gas chromatography–electron-capture detection (GC–ECD). Severe carryover between samples (e.g., 20%) occurs on both stir bars and the SPME fibers demonstrating that it is important to use a new stir bar for each sample, as well as to perform SPME–GC blanks between samples to avoid quantitative errors. The equilibrium partitioning coefficients of individual PCB congeners between PDMS and water were found to be surprisingly different compared to their octanol–water partitioning coefficient (K_ow), demonstrating that K_ow cannot be used to estimate the partitioning behavior of PCBs in the SPME process. Using a 15-min SPME extraction, SPME analysis with GC–ECD was linear (r²≥0.97) from 5 pg/ml to the solubility limit of each congener. Concentrations in water samples obtained by 15-min SPME extractions compared favorably with those obtained by toluene extractions, demonstrating that SPME combined with GC is a useful technique for the rapid determination of PCBs in water samples.     

Solid-phase microextraction for organochlorine pesticide residues analysis in Chinese herbal formulations

Solid-phase microextraction (SPME) coupled with gas chromatography-mass spectrometry (GC-MS) was used to determine pesticide residues in Chinese herbal formulations. Fibers coated with a 100-microm film thickness of poly(dimethylsiloxane) was used to extract 19 organochlorine pesticides (OCPs). The pesticides in the study consisted of alpha-, beta-, gamma-and delta-hexachlorocyclohexane, p,p'-DDD, p,p'-DDE, p,p'-DDT, o,p'-DDT, aldrin, dieldrin, endrin, endrin aldehyde, endrin ketone, endosulfan (I, II and sulfate), heptachlor, heptachlor epoxide, and methoxychlor. The optimal experimental procedures for the adsorption and desorption of pesticides were evaluated. The linearity was obtained with a precision below 11% RSD for the studied pesticides expect endosulfan sulfate (21%) in a wide range from 1 to 200 ng/g. Detection limits were reached at below ng/g levels. Heptachlor epoxide was determined at a calculated limit of 0.03 ng/g. Comparison between SPME and Soxhlet extraction showed that SPME has a less than one order detection limit for residue pesticide determination. The proposed method was tested by analyzing herbal formulations from a local market for OCP multiresidues. Some residues studied were detected in the analyzed samples. The results demonstrate the suitability of the SPME-GC-MS approach for the analysis of multi-residue OCPs in Chinese herbal formulations.     

Solid-phase microextraction: a promising technique for sample preparation in environmental analysis

Solid-phase microextraction (SPME) is a simple and effective adsorption and desorption technique, which eliminates the need for solvents or complicated apparatus, for concentrating volatile or nonvolatile compounds in liquid samples or headspace. SPME is compatible with analyte separation and detection by gas chromatography and high-performance liquid chromatography, and provides linear results for wide concentrations of analytes. By controlling the polarity and thickness of the coating on the fibre, maintaining consistent sampling time, and adjusting other extraction parameters, an analyst can ensure highly consistent, quantifiable results for low concentration analytes. To date, about 400 articles on SPME have been published in different fields, including environment (water, soil, air), food, natural products, pharmaceuticals, biology, toxicology, forensics and theory. As the scope of SPME grew, new improvements were made with the appearance of new coatings that allowed an increase in the specificity of this extraction technique. The key part of the SPME fibre is of course the fibre coating. At the moment, 27 variations of fibre coating and size are available. Among the newest are a fibre assembly with a dual coating of divinylbenzene and Carboxen suspended in poly(dimethylsiloxane), and a series of 23 gauge fibres intended for specific septumless injection system. The growth of SPME is also reflected in the expanding number of the accessories that make the technology even easier to use Also available is a portable field sampler which is a self-contained unit that stores the SPME fibre after sampling and during the shipment to the laboratory. Several scientific publications show the results obtained in inter-laboratory validation studies in which SPME was applied to determine the presence of different organic compounds at ppt levels, which demonstrates the reliability of this extraction technique for quantitative analysis.     

Solid-phase microextraction for the analysis of short-chain chlorinated paraffins in water samples

A novel solid-phase microextraction (SPME) method coupled to gas chromatography with electron capture detection (GC-ECD) was developed as an alternative to liquid-liquid and solid-phase extraction for the analysis of short-chain chlorinated paraffins (SCCPs) in water samples. The extraction efficiency of five different commercially available fibres was evaluated and the 100-microm polydimethylsiloxane coating was the most suitable for the absorption of the SCCPs. Optimisation of several SPME parameters, such as extraction time and temperature, ionic strength and desorption time, was performed. Quality parameters were established using Milli-Q, tap water and river water. Linearity ranged between 0.06 and 6 microg l(-1) for spiked Milli-Q water and between 0.6 and 6 microg l(-1) for natural waters. The precision of the SPME-GC-ECD method for the three aqueous matrices was similar and gave relative standard deviations (RSD) between 12 and 14%. The limit of detection (LOD) was 0.02 microg l(-1) for Milli-Q water and 0.3 microg l(-1) for both tap water and river water. The optimised SPME-GC-ECD method was successfully applied to the determination of SCCPs in river water samples.     

固相微萃取-气相色谱-红外光谱联用技术分析水处理药剂

在循环水系统中,水处理药剂起着重要的作用,它可以缓蚀阻垢,还可抑制细菌增长,提高水源质量.开发水处理药剂有着广泛的市场.水处理药剂的组成不同性能会有所差别,分析不同组成的药剂从而有针对性地开发新品种,加快了产出速度.本文利用固相微萃取-气相色谱-红外光谱联用技术对某水处理药剂进行了剖析,从而为开发新型药剂提供了依据,节约了开发周期.固相微萃取技术是90年代发展的一种集萃取,浓缩,进样于一体的样品前处理方法.基本的固相微萃取是通过石英纤维头表面涂渍的高分子层对样器中直接热解吸,使样品预处理过程大为简化,提高了分析速度和灵敏度,其检出限的数量级位ng/g～pg/g,相对标准偏差小于30%,线性范围为3～5个数量级.气相色谱-红外光谱联用技术结合了气相色谱分离性能高的特点和红外光谱的定性能力较强的特点,在实验过程中对于色谱条件我们选用固相微萃取技术,大大提高了检出度,通过改善气相色谱分离条件,很好地分析了水处理药剂中的组成.根据相似相容原理,结合分析物的极性,沸点和分配系数,选用了聚二甲基硅氧烷涂层萃取纤维;通过考虑分析物的分配系数,物质的扩散速率,样品基质,样品体积,萃取头膜厚等因素萃取时间选为5 min;选择热辑吸时间为3 min,进样口温度为300℃时,解析完全.利用程序升温,检测出10余个组分,对其中10个组分给出定性结果,依保留时间增大顺序,检出的10个峰分别为:水,1,2丙二醇,N,N二甲基十二烷基胺,癸醛,硫醇,N,N二甲基十二烷基胺同系物,1-溴十一烷,N,甲基二辛胺及其同系物等.定性结果与红外标准谱的匹配率均在90%以上.结果表明,该水处理药剂含有氮-氮类化合物,这类化合物正是发挥药剂作用的核心.     

Solid-phase microextraction for herbicide determination in environmental samples

Liquid-liquid extraction or solid-phase extraction followed by gas chromatography (GC) or high-performance liquid chromatography are traditional herbicide residue determination methods for environmental samples. Solid-phase microextraction (SPME) is a solventless, fast, and sensitive alternative herbicide residue extraction method that can be applied to numerous environmental matrices. The objective of this paper was to review SPME literature regarding extraction theory, extraction modes, fiber types, and method optimization in conjunction with present and future SPME applications for herbicide determination in environmental samples.     

Solid-phase microextraction using pencil lead as sorbent for analysis of organic pollutants in water

Most solid-phase microextraction methods are based on poly (dimethylsiloxane)-coated silica fibers. Is the present study, pencil lead was used as an alternative sorbent for solid-phase imcroextraction. Its application to three organic pollutants with different polarity in water was investigated. The detection limit for determination by gas chromatography with electron capture detector was 0.005 ng ml⁻¹ for lindane, 0.05 ng ml⁻¹ for methyl parathion and 1 ng ml⁻¹ for 2-chlorophenol. The presence of dissolved humic substances (10 mg l⁻¹) in water did not affect the extraction of the three analytes.     

Solid-phase microextraction coupled to liquid chromatography for the analysis of phenolic compounds in water

Solid-phase microextraction (SPME) coupled to high-performance liquid chromatography (HPLC) has been applied to the analysis of priority pollutant phenolic compounds in water samples. Two types of polar fibers [50 microm Carbowax-templated resin (CW-TPR) and 60 microm polydimethylsiloxane-divinylbenzene (PDMS-DVB)] were evaluated. The effects of equilibration time and ionic strength of samples on the adsorption step were studied. The parameters affecting the desorption process, such as desorption mode, solvent composition and desorption time, were optimized. The developed method was used to determine the phenols in spiked river water samples collected in the Douro River, Portugal. Detection limits of 1-10 microg l(-1) were achieved under the optimized conditions.     

Solid-phase microextraction of hydrocarbons from water in a centrifuge

The results of our study of solid-phase microextraction of substances using a centrifuge for determining the microquantities of hydrocarbon impurities in water are presented. The cartridge diameter, sorbent mass, and solvent volume were shown to affect the percent extraction of substances and the analytical signal intensity. The relationship between the cartridge geometry, the sorbent mass, and the solvent volume was considered.     

Solid-phase microextraction with on-fiber derivatization for the analysis of anti-inflammatory drugs in water samples

A sensitive and solvent-free procedure for the determination of non-steroidal acidic anti-inflammatory drugs in water samples was optimized using solid-phase microextraction (SPME) followed by on-fiber silylation of the acidic compounds and gas chromatography-mass spectrometry (GC-MS) determination. Microextraction was carried out directly over the filtered water samples using a polyacrylate fiber. Derivatization was performed placing the SPME fiber, loaded with the extracted analytes, in the headspace of a vial containing 50 microl of N-methyl-N-(tert-butyldimethylsilyl)-trifluoroacetamide (MTBSTFA). Derivatives were desorbed for 3 min in the GC injector. Influence of several parameters in the efficiency of microextraction (volume of sample, time, pH, type of fiber coating, etc.) and derivatization steps (time, temperature and volume of MTBSTFA) was systematically investigated. In the optimal conditions an excellent linearity over three orders of magnitude and quantification limits at the ng/l level (from 12 to 40 ng/l) were achieved. The proposed method was applied to the determination of acidic compounds in sewage water and results compared to those obtained using solid-phase extraction (SPE) followed by the derivatization of the compounds in the organic extract of the solid-phase extraction cartridge.     

Solid-phase microextraction with on-fibre derivatisation applied to the analysis of volatile carbonyl compounds

We have used a fast, sensitive and efficient method for the analysis of volatile carbonyl compounds (saturated aliphatic and unsaturated aldehydes) based on solid-phase microextraction with on-fibre derivatisation. Pentafluorophenylhydrazine was absorbed onto a poly(dimethylsiloxane)/divinylbenzene-coated fibre and exposed to the vapours of aldehyde-containing matrices. The hydrazones formed on the fibre were desorbed into the gas chromatograph injection port and quantified by means of electron-capture detection with high sensitivity (10-90 fmol) and good reproducibility (RSD<10%). The method was applied to the headspace-sampling of volatile carbonyl compounds released during the thermally-induced degradation of sunflower oil.     

Solid-phase microextraction in bioanalysis: New devices and directions

The primary objective of this review is to discuss recent technological developments in the field of solid-phase microextraction that have enhanced the utility of this sample preparation technique in the field of bioanalysis. These developments include introduction of various new biocompatible coating phases suitable for bioanalysis, such as commercial prototype in vivo SPME devices, as well as the development of sampling interfaces that extend the use of this methodology to small animals such as mice. These new devices permit application of in vivo SPME to a variety of analyses, including pharmacokinetics, bioaccumulation and metabolomics studies, with good temporal and spatial resolution. New calibration approaches have also been introduced to facilitate in vivo studies and provide fast and quantitative results without the need to achieve equilibrium. In combination with the drastic improvement in the analytical sensitivity of modern liquid chromatography–tandem mass spectrometry instrumentation, full potential of in vivo SPME as a sample preparation tool in life sciences can finally be explored. From the instrumentation perspective, SPME was successfully automated in 96-well format for the first time. This opens up new opportunities for high-throughput applications (>1000 samples/day) such as for the determination of unbound and total drug concentrations in complex matrices such as whole blood with no need for sample pretreatment, studies of distribution of drugs in various compartments and/or determination of plasma protein binding and other ligand–receptor binding studies, and this review will summarize the progress in this research area to date.     

Solid-phase microextraction: a powerful sample preparation tool prior to mass spectrometric analysis

Sample preparation is an essential step in analysis, greatly influencing the reliability and accuracy of resulted the time and cost of analysis. Solid-Phase Microextraction (SPME) is a very simple and efficient, solventless sample preparation method, invented by Pawliszyn in 1989. SPME has been widely used in different fields of analytical chemistry since its first applications to environmental and food analysis and is ideally suited for coupling with mass spectrometry (MS). All steps of the conventional liquid-liquid extraction (LLE) such as extraction, concentration, (derivatization) and transfer to the chromatograph are integrated into one step and one device, considerably simplifying the sample preparation procedure. It uses a fused-silica fibre that is coated on the outside with an appropriate stationary phase. The analytes in the sample are directly extracted to the fibre coating. The SPME technique can be routinely used in combination with gas chromatography, high-performance liquid chromatography and capillary electrophoresis and places no restriction on MS. SPME reduces the time necessary for sample preparation, decreases purchase and disposal costs of solvents and can improve detection limits. The SPME technique is ideally suited for MS applications, combining a simple and efficient sample preparation with versatile and sensitive detection. This review summarizes analytical characteristics and variants of the SPME technique and its applications in combination with MS.     

Solid-phase microextraction for gas chromatographic/mass spectrometric analysis of dimethoate in human biological samples

A new, simple and rapid procedure for the determination of dimethoate in urine and blood samples was developed using direct immersion solid-phase microextraction and gas chromatography/mass spectrometry. This technique required only 0.1 mL of sample, and ethion was used as internal standard. Two types of coated fibre were compared (100 microm polydimethylsiloxane, and 65 microm Carbowax/divinylbenzene). Other parameters, such as extraction temperature, adsorption and desorption time, salt addition, agitation and pH, were optimized to enhance the sensitivity of the method. Limits of detection (LODs) and quantitation (LOQs) were 50 and 100 ng/mL for urine and 200 and 500 ng/mL for blood, respectively. The method was found to be linear between the LOQ and 40 microg/mL for urine, and between the LOQ and 50 microg/mL for blood, with correlation coefficients ranging from 0.9923-0.9996. Precision (intra- and interday) and accuracy were in conformity with the criteria normally accepted in bioanalytical method validation. The mean absolute recoveries of dimethoate were 1.24 and 0.50% for urine and blood, respectively. Because of its simplicity and the fact that small volumes of sample are used, the described method can be successfully used in the diagnosis of poisoning by this pesticide, namely in those situations where the sample volume is limited, as frequently occurs in forensic toxicology.