Current trends in solid phase based extr

() Review Current trends in solid phase based extraction techniques for the determination of pesticides in food and environment Yolanda Picó, Mónica Fernández, Maria Jose Ruiz, Guillermina Font ⁎ Labo[.]

J Biochem Biophys Methods 70 (2007) 117 – 131 www.elsevier.com/locate/jbbm Review Current trends in solid-phase-based extraction techniques for the determination of pesticides in food and environment Yolanda Picó, Mónica Fernández, Maria Jose Ruiz, Guillermina Font ⁎ Laboratori de Bromatologia i Toxicologia, Facultat de Farmácia, Universitat de Valencia, Av Vicent Andrés Estellés s/n, 46100 Burjassot, Valencia, Spain Received 30 May 2006; accepted 27 October 2006 Abstract Solid-phase extraction (SPE) procedures for pesticide residues in food and environment are reviewed and discussed The use of these procedures, which include several approaches such as: matrix solid-phase dispersion (MSPD), solid-phase micro-extraction (SPME) and stir-bar sorptive extraction (SBSE), represents an opportunity to reduce analysis time, solvent consumption, and overall cost SPE techniques differ from solvent extraction depending on the interactions between a sorbent and the pesticide This interaction may be specific for a particular pesticide, as in the interaction with an immunosorbent, or non-specific, as in the way a number of different pesticides are adsorbed on apolar or polar materials A variety of applications were classified according to the method applied: conventional SPE, SPME, hollow-fiber micro-extraction (HFME), MSPD and SBSE Emphasis is placed on the multiresidue analysis of liquid and solid samples © 2006 Elsevier B.V All rights reserved Keywords: Solid-phase extraction; Solid-phase micro-extraction; Hollow-fiber micro-extraction; Stir-bar sorptive extraction; Matrix solid-phase dispersion; Food Contents Introduction Solid-phase-based extraction techniques 2.1 Solid-phase extraction 2.2 Solid-phase micro-extraction 2.3 In-tube solid-phase micro-extraction 2.4 Matrix solid-phase dispersion 2.5 Stir-bar sorptive extraction Applications Conclusions Acknowledgments References Introduction The analysis of pesticide residues in food and environmental samples has received increasing attention in the last few decades, as can be deduced from the great number of papers ⁎ Corresponding author Tel.: +34 96 3544295; fax: +34 96 3544954 E-mail address: guillermina.font@uv.es (G Font) 0165-022X/$ - see front matter © 2006 Elsevier B.V All rights reserved doi:10.1016/j.jbbm.2006.10.010 117 118 118 119 121 121 122 128 129 129 129 published dealing with this subject [1–4] These compounds are usually determined by gas chromatography (GC), liquid chromatography (LC) or capillary electrophoresis (CE), depending on their polarity, volatility, and thermal stability [5–9] Regulatory authorities provide assurance that any pesticide remaining in or on the food is within safe limits through monitoring programs or random sampling and analysis of raw or processed food on the market In response to this requirement a number of methods have been developed and 118 Y Picó et al / J Biochem Biophys Methods 70 (2007) 117–131 applied routinely for the control of pesticide residues in food and environment [4,10,11] In general, food and environmental samples cannot be analyzed without some preliminary sample preparation, because contaminants are too diluted and the matrix is rather complex [2,4] Due to the low detection levels required by regulatory bodies and the complex nature of the matrices in which the target compounds are present, efficient sample preparation and trace-level detection and identification are important aspects of analytical methods [4] Sample preparation, such as extraction, concentration, and isolation of analytes, greatly influences the reliability and accuracy of their analysis [2] In recent years, many innovations in the analytical processes that can be applied to prepare food and environmental samples for extraction and determination of pesticide residues have been developed [12–20] This has resulted in the recognition that classical methods can now be replaced with procedures that are faster, less expensive, and equal to or better than classical methods Although most officially methods for the analysis of pesticides use liquid/liquid extraction (LLE), solid-phase extraction (SPE) has been developed as an alternative, owing to its simplicity and economy in terms of time and solvent needs [21,22] This technique has gained wide acceptance because of the inherent disadvantages of LLE, e.g., it is unable to extract polar pesticides, it is laborious and time-consuming, expensive, and apt to form emulsions, it requires the evaporation of large volumes of solvents and the disposal of toxic or flammable chemicals In addition, recent regulations pertaining to the use of organic solvents have made LLE techniques unacceptable Alternative solid-phase-based extraction techniques, which reduce or eliminate the use of solvents, can be employed to prepare samples for chromatographic analysis These include SPE, solid phase micro-extraction (SPME), matrix solid-phase dispersion (MSPD), and stir-bar sorptive extraction (SBSE) [15,17–20] The ideal sample preparation methodology should be fast, accurate, precise, and consumes little solvent Further- more, this sample preparation should be easily adapted for field work and employs less costly materials [2] The solid-phasebased extraction techniques could be the isolation techniques capable of meeting these expectations The extraction of analytes from solid matrices is an active development area in sample preparation technology [21] Moreover, there has been an increasing demand for new extraction techniques amenable to automation with shortened extraction times and reduced organic solvent consumption [23] Several other sample preparation methods for organic compounds are supercritical-fluid extraction (SFE) [13] and solid–fluid– fluidizing series extraction procedures, named fluidized-bed extraction (FBE) [23] However, the application of SPE technology to the isolation of pesticides and related compounds has grown enormously [15,17,21] The aim of this review is to describe the current trends of SPE of pesticides with special emphasis on articles published in the last three years The solid-phase-based extraction procedures developed to isolate and pre-concentrate pesticide residues as well as the principles and relative merits of each procedure are summarized and discussed Isolation and pretreatment steps in SPE of pesticide residues in food and environmental matrices are outlined An overview of practical application is given for SPE, SPME, in-tube SPME, MSPD, and SBSE methods Solid-phase-based extraction techniques 2.1 Solid-phase extraction The SPE technique was first introduced in the mid-1970s [16] It became commercially available in 1978, and now SPE cartridges and disks are available from many suppliers Conventional SPE is generally performed by passing aqueous samples through a solid sorbent in a column Pesticides are eluted from the solid medium with an appropriate organic Fig GC/MS chromatogram of pesticide-spiked lemon essential oil (from Barrek et al [43]) Y Picó et al / J Biochem Biophys Methods 70 (2007) 117–131 solvent One highly important aspect in SPE is the selection of the sorbent C-18 bonded silicas and styrene/divinyl benzene co-polymers are the most frequently used This technique is widely applied to water samples [14,16,22,24–39] For liquid foods, such as fruit juices, wine, and milk, acceptable recoveries can be obtained Before SPE can be applied to a solid matrix (soil, vegetables and fruits), a separate homogenization step and, often, filtration, sonication, centrifugation, and liquid/ liquid clean-up are required [34,40–56] However, the presence of interfering substances, such as salts, humic acids, and other humic substances in water; or proteins, lipids, and carbohydrates in food; makes the determination of polar or early-eluted pesticides, difficult or impossible The use of selective solid phases, such as immunosorbents or molecularly imprinted polymers (MIPs) can solve these problems MIPs are used preferentially, because of their low cost compared with immunosorbents [25,57] Compatibility of reversed-phase (RP) LC systems with aqueous samples allows on-line coupling of SPE with the analytical system This on-line system is generalized for water samples and typically handles the pre-concentration of analytes from 50- to 250-ml aqueous samples on a small cartridge, packed with a suitable sorbent Subsequent gradient elution of the trapped analytes into an analytical column or detection system is carried out Automated SPE on-line sample handling can be performed with commercially available equipment, with hand-made cartridges, and six-port switching valves [31,58,59] The advantages of on-line systems are: analyte enrichment, automated sample preparation and analysis, and minimized losses The disadvantages of the on-line pre-concentration are the reduced sample throughput, since only small sample volumes can be processed, and lack of versatility of the system The direct coupling of SPE with GC is more difficult, because it requires effective elimination of traces of water There are some analytical methodologies that use automated SPE, followed by large-volume injection (LVI) by injectors with programmable temperature vaporization (PTV), in combination with GC/MS [28] This system provides a fast, reproducible, and sensitive technique for pesticide determination in drinking water The use of fully automated on-line RP–LC/GC has also been reported, mainly for the determination of pesticide residues in olive oil This procedure, in conjunction with the through-oven transfer adsorption/desorption (TOTAD) interface can be carried out without any other sample pre-treatment than a simple filtration [44] Automated, coupled on-line LC/GC systems have numerous advantages, especially when a large number of samples is to be analyzed High sample throughput, as practiced routinely in pharmacokinetic screening, is now expanding rapidly in other sectors, such as environmental and food analysis However, the majority of reports on the application of on-line SPE describe environmental monitoring of aqueous samples with only a few for food analysis, e.g., mepiquat and chlormequat in pears, tomatoes, and wheat flour [60], and Nmethylcarbamates and their metabolites in soil and food [61] Fig shows a gas chromatogram in SIM mode for a spiked sample of lemon essential oil, previously extracted with a Florisil cartridge The temperature ramp is an important step, 119 because it allowed elimination of residual volatile constituents of the matrix, remaining after SPE extraction [43] 2.2 Solid-phase micro-extraction SPME was first developed in 1989 by Pawliszyn and coworkers and has been marketed by Supelco since 1993 Subsequently, the technique has grown enormously [18–20] It can integrate sampling, extraction, pre-concentration, and sample introduction into a single uninterrupted process resulting in high sample throughput A large number of fiber coatings based on solid sorbents are now available, in addition to the original general-purpose poly(dimethylsiloxane) (PDMS) and poly(acrilate) (PA) coated fibers, namely: PDMS/divinylbenzene (DVB), Carbowax/DVB, Carbowax/template resin (TR), Carboxen/ PDMS, and DVB/Carboxen/PDMS-coated fibers Extraction of Fig SPME/GC/AED chromatograms obtained from a honey sample, previously fortified with a standard mixture of pesticides: (A) S-181 nm; (B) Cl-479 nm; (C) Br-478 nm = 100 ng/g chlordimeform, = 150 ng/g dimethoate, = ng/g aldrin, = 20 ng/g parathion-ethyl, = 80 ng/g captan, = 20 ng/g chlorfenvinphos, = ng/g dieldrin, = ng/g p,p'-DDE, = 0.5 ng/g p,p'-DDD, 10 = ng/g p,p'-DDT, 11 = 10 ng/g bromopropylate, 12 = ng/g tetradifon, 13 = 60 ng/g azinphos-methyl, 14 = 20 ng/g λ-cyalothrin, 15 = ng/g cumaphos, 16 = 100 ng/g deltamethrin (from Campillo et al [67]) 120 Y Picó et al / J Biochem Biophys Methods 70 (2007) 117–131 analytes by the new porous polymer SPME fibers with mixed coating is primarily based on adsorption rather than absorption Some of these porous polymer SPME fibers with bipolar characteristics can be very useful for the simultaneous analysis of pesticides, enlarging the spectrum of SPME applications [62–65] Since its introduction, SPME has gained popularity as a simple solvent-free, reliable, and flexible tool for the sampling of a variety of volatile and semi-volatile compounds SPME has extensively been used for the direct extraction of pesticides from aqueous samples [63,66–74] On the other hand, fruit and vegetables, being mostly in solid or heterogeneous form, not allow direct extraction However, it is possible to analyze them by SPME after a previous solvent extraction [62,75,76] The SPME fiber can also be suspended in the headspace above the homogenized sample This option, named headspace-SPME (HS-SPME), eliminates interferences, because the fiber is not in contact with the complex matrices of fruits and vegetables Several classes of pesticide residues have been extracted from complex matrices with HSSPME [77–82] In contrast to the more conventional extraction methods, SPME does not endeavour to extract all or even most of the analytes from a sample It is this aspect of SPME that can make calibration problematic Calibration in SPME is usually performed by spiking standards, prepared in pure water For typical heterogeneous environmental samples, the assumption is that an SPME fiber would come to equilibrium with only the freely dissolved analytes in the water phase or the analytes in the vapor phase, depending on the methodology used However, in such a sample the fiber actually directly interacts with each phase in the sample For example, as an analyte is depleted from the dissolved phase by sorption on the fiber, the analyte is subsequently replenished via re-equilibration in the other phases in the sample Although recoveries are usually low (ca 30%), the good repeatability and reproducibility of the methods allows satisfactory quantification of the analytes [66,69,70,83] Fig Chromatogram obtained by using a proposed procedure for the new SPME fiber on the spiked samples of 10 ng ml− of each organophosphorus pesticide (A) water and (B) apple juice Peak identification: = dichlorvos, = phorate, = diazinon, = methyl parathion, = fenitrotion, = malathion, = parathion, = ethion (from Linghsuang et al [62]) Y Picó et al / J Biochem Biophys Methods 70 (2007) 117–131 The most common procedure for desorbing analytes from the fiber in SPME is thermal desorption in the injector of a gas chromatograph, because this desorption method completely eliminates the use of organic solvents [66,69,79,83] The analytes adsorbed on the fibers can also be desorbed by using a polar organic solvent, such as MeOH or acetonitrile [84] This approach is used to combine this extraction technique with LC or CE For LC, there is a commercial device that allow desorption of all analytes accumulated in the fiber directly into the LC injector This system provides enhanced sensitivity [85] There are two ways of desorbing analytes from the fiber [83] When the analytes are not strongly adsorbed on the fiber, the dynamic mode of desorption by a moving stream of mobile phase is sufficient But when the analytes are more strongly adsorbed on the fiber, the fiber is dipped in the mobile phase or other strong solvent for a specified time Desorption performed in this way is known as static desorption Fig illustrates the elution profiles obtained at different channels from fortified honey, using a nonpolar (100-μm) PDMS As can be observed, the lack of interfering peaks provides unequivocal identification [67] The sample matrix can affect the SPME extraction efficiency Fig shows the chromatogram of apple juice compared with that of pure water containing the same concentration of organophosphorus pesticides, obtained with a vinyl crown ether polar fiber The amounts of dichlorvos, malathion, and ethion extracted from apple juice were much less than those from pure water [62] 2.3 In-tube solid-phase micro-extraction In-tube SPME is a relatively new micro-extraction and preconcentration technique, which can be easily coupled on-line 121 with LC An open-tubular capillary column with cross-linked PDMS coating can be used to trap the analytes A drying step is necessary before the enriched compounds can be analyzed by thermodesorption and GC [12,86,87] When a sample contains non-volatile high-molecular interfering compounds, such as proteins, humics acids, and fatty material, analysis by means of in-tube SPME is difficult To overcome this difficulty, a porous cellulose filter, protecting the coating, has been used to determine pesticides [88,89] On-line in-tube SPME continuous extraction, concentration, desorption, and injection with an autosampler, is commonly used in combination with LC and LC/MS 2.4 Matrix solid-phase dispersion In 1989, MSPD, a process for the extraction of solid samples was introduced by Barker et al [17] MSPD performs sample disruption while dispersing its components into a solid support MSPD combines sample homogenization with preliminary clean-up of the analytes [15] The method involves the dispersion of the sample in a solid sorbent, followed by preliminary purification and the elution of the analytes with a relative small volume of solvent The extracts obtained are generally ready for analysis, but, if necessary, they can easily be subjected to direct extract purification [90] MSPD has demonstrated its usefulness in several difficult determinations [91–93] The most widely used procedure for separating pesticides from the olive oil matrix has been sizeexclusion chromatography (SEC) However, the main pitfalls associated with this methodology are the use of large amounts of organic solvents and the lack of flexibility to change from Fig Comparison of GC/MS full-scan olive oil matrix chromatograms, obtained by size-exclusion chromatography (SEC) and matrix solid-phase dispersion (MSPD) extraction (from Ferrer et al [92]) 122 Y Picó et al / J Biochem Biophys Methods 70 (2007) 117–131 one method to another Moreover, the separation of the pesticide fraction (which has a low molecular weight) from the whole fatty matrix (mainly triglycerides) is very difficult to accomplish by SEC, because those two fractions are partially overlapping Normally, a compromise between purity of the extract (minimizing the amount of fat in the pesticide fraction) and acceptable pesticide recoveries must be made This usually involves the lost of some of the pesticides [92], thus yielding lower mean percentage recoveries These drawbacks can be partially circumvented with the use of the MSPD, which involves less reagent consumption and waste generation and provides more flexibility In addition, the resultant extracts are cleaner than those obtained by SEC, as can be seen in Fig 4, where the full-scan GC/MS olive oil matrix chromatogram obtained by means of SEC is compared with that obtained with MSPD The chromatogram obtained by extraction with the MSPD method was much cleaner than that obtained with SEC at two different collection times of the pesticide fraction This illustrates the capabilities of MSPD to provide clean extracts of such complex matrices with a high fat content 2.5 Stir-bar sorptive extraction In 1999, a new extraction technique was developed by Baltusen et al [94] In this extraction technique, known as stirbar sorptive extraction (SBSE), a magnetic stir bar, coated with 50–300 μl of polydimethylsiloxane (PDMS), is used The extraction mechanisms and advantages are similar to those of SPME, but the enrichment factor, which is determined by the amount of extractive phase is up to 100 times higher In SBSE, analytes are adsorbed on a magnetic rod, coated with PDMS, by stirring with it for a given time After that, the stir bar is either thermally desorbed on-line with capillary GC/MS or by organic solvents to be subsequently injected into an LC system [95] Fig GC/TSD chromatograms of organophosphorus pesticides, obtained by an optimized SBSE method from: (A) water solution (800 ng/l); (B) spiked cucumber sample (0.5 ng/g) and (C) a potato incurred sample = monocrotophos, = phorate, = dimethoate, = parathion-methyl, = malathion, = fenitrothion, = fenthion, = chlorpyrifos, = parathion, 10 = methidathion, 11 = triazophos, 12 = ethion (from Liu et al [96]) Table SPE methods for pesticides Matrices Pre-treatment Characteristics Elution Recovery (%) Detection LOD's (μg/l) LOQ's (mg/kg) Reference Fruits and vegetables Aqueous sample extract passed through the C18 column CE – 0.2–0.5 [97] Samples homogenized with water:MeCN (50:50) for 15 acetone was evaporated Extract passed through the C18 column Samples passed through tC18 cartridge 58–99 CE/MS 50–200 (CE–MS) – [40] 64–85 GC/MS 0.02–0.038 – [24] Triazines (6) and metabolites (5) River and tap water Pesticides eluted with DCM Concentrated to dryness and redisolved in 0.5 ml of buffer Pesticides eluted with DCM Concentrated to dryness and redisolved in 0.5 ml of buffer Carbamates eluted with ml MeCN Concentrated to dryness and redisolved in 0.5 ml of MeCN Triazines eluted with MeCN:acetic acid (9:1) Concentrated to dryness and redisolved in 0.5 ml of water: MeCN (9:1) 31–106 Peach and nectarine MFE C18 solid phase (45- to 55-μm particle diameter and 60 Å pore diameter) C18 solid phase LC/DAD UV 0.03–0.2 – [25] Organochlorine pesticides (13) Surface water 72–119 LC/MS/MS 0.0008– 0.083 – [26] Neonicotinoid pesticides (4) Pesticides eluted with ethyl acetate Evaporated to dryness and redissolved in 250 μl of 40 ng/ml 2,4-dichlorophenol in MeCN as internal standard Pesticides eluted with DCM Evaporated at 40 °C under vacuum and redissolved in ml of MeOH Pesticides eluted with MeCN Evaporated to dryness under vacuum and redissolved in ml MECN and 200 μl of 16 mM ammonium carbonate solution 75–105 LC/ESI/MS – 0.1–0.5 [41] 50–84 CE/UV 18–34 (μg/kg) – [42] Pesticides eluted with MeCN Evaporated to dryness at 40 °C and redissolved in ml MeCN n-hexane:DCM (1:1, v/v), concentrated to dryness and redissolved in 0.5 ml n-hexane Pesticides eluted with DCM Extracts concentrated at 30 °C Pesticides eluted with DCM Extracts concentrated at 30 °C Pesticides desorbed with 0.5 ml of ethyl acetate MeCN MeOH Mobile phase of LC 55–110 CE/UV 0.13–0.34 – [27] 69–96 GC/ECD; GC/MS – 0.004–0.09 [98] 67–107 GC/MS 30–400 – [43] 50–115 LC/MS 20–60 – [43] – GC/MS 10–50 (ng/l) [28] LC/UV TLC plates LC/ESI– MS/MS 10–30 10 0.011–7.4 (ng/l) 33–166 (ng/l) 35–100 (μg/l) 30 (μg/l) 0.004–2.8 (ng/l) GC/FID 0.18–0.38 mg/l LC/ Fluorescence 0.01–0.02 (μg/l) Water Sep-Pak tC18 cartridges Pre-concentration of water Prior the SPE, high-hardness water (40 °f) washed with HCl SPE with propazine-MIP and mixtures of LiChrolut EN propazine-MIP Water samples containing 1% MeCN were pre-concentrated through C18E cartridges Selective MIP cartridges for triazines and related metabolites Metabolites extracted by SPE with a mixture of propazine-MIP and LiChrolut EN Strata C18E cartridges Apricot, celery, courgette, peach, pear Samples homogenized with acetone for in mixer at 9500 rpm Extrelut-NT20 cartridge Triazolopyrimidine pesticides (5) Soils Sep-Pak Plus C18 cartridges Triazolopyrimidine pesticides (5) Water Organochlorines (11), pyretroids (5) Tea Pesticides (12) Oils of citrus fruit Pesticides (12) Oils of citrus fruit Organochlorine pesticides Drinking water Soil samples extracted with water and 0.1 M NaOH in ultrasonic bath for 20 Centrifuged at 4000 rpm for 10 to separate the supernatant Added HCl and passed to C18 SPE cartridge Water samples containing hydrochloric acid were pre-concentrated through C18 SPE cartridges Samples extracted by vortex gyrator a full speed for Centrifuged at 3000 rpm for Supernatant layers were extracted Samples homogenized in an ultrasonic bath for 15 Extract passed through a Florisil cartridge Samples homogenized in an ultrasonic bath for 15 Extract passed through a Florisil cartridge Samples passed through C18 cartridge Urea (3), 2,4-D and amitrine Triazines (6) Triazines, phenylureas, organophosphorus, anilines, acidic, propnil, molinate Organophosphorus (4) Water Water Water Samples passed through C18 cartridge Samples passed through C18 cartridge None 1.0 g C18 bonded silica phase Backerbond SPE C-18 polar On-line trace enrichment Olives Filtering of the olive oil Benzoylureas (5) Water Filtering LC/GC on-line LC column C4,Chromasil C-18 short column Sep-Pak Plus C18 cartridges Florisil column preconditioned with n-hexane FL-PR extraction cartridge FL-PR extraction cartridge SPE-LVI MeOH/water Mobile phase (MeOH/water gradient program) 7–91 98–104 88–95 – – 92–109 Y Picó et al / J Biochem Biophys Methods 70 (2007) 117–131 Analyte Azole (1), insect growth regulator (1), pyrethroid (1), pyrrole (1), triazole (4) Azole (1), insect growth regulator (1), pyrethroid (1), pyrrole (1), triazole (4) Carbamates (7) [29] [30] [31] [44] 0.04–0.05 (μg/l) [32] MIP: molecularly imprinted polymer; °f: French degrees; LiChrolut EN: polymeric sorbent of styrene divinylbenzene; DCM: dichloromethane; LVI: large volume injection; MeCN: acetonitrile; TLC: thin layer chromatography 123 124 Table SPME methods for pesticides Analyte Matrices Pre-treatment Characteristics Elution Molinate Rice field and water Water Direct SPME: ml stirred sample with 200 g/l sodium sulfate and internal standard for 30 HS-SPME: ml sample with ml HOAc/NaOAc buffer and internal standard solution added In situ derivation with 300 μl of 1% NaBEt4 sol Vigorously shaken in ultrasonic bath for 10 and extracted for 30 at 80 °C Direct SPME: ml stirred sample with 30% NaCl 30 at 25 °C DVB/CAR/PDMS Fenbutatin oxide Detection LOD Reference Desorption at 220 °C for 79–97 GC/FPD 0.48–5.2 μg/l [70] 100 μm PDMS Desorption at 250 °C for – GC/MS 16 ng/l [99] 85 μm PA Desorption at 175 °C for – 0.5 μg/l [66] 85 μm PA Desorption at 175 °C for – 0.001 mg/kg [66] 100 μm PDMS Desorption at 240 °C for – 20–100 ng/l [68] 100 μm PDMS – GC/ECD/ NPD GC/ECD/ NPD GC/MS GC/FID LC/UV (254 nm) LC/DAD LC/DCAD GC/MS 1–10 ng/ml [69] 1.2–11.8 μg/l [83] 1.3–15 ng/l [77] 1,3-dichloropropene methyl isothiocyanate 1,3-dichloropropene methyl isothiocyanate Irganrol-1051 related s-triazine degradation products (M1 and M2) Nabam thiram azamethiphos Water Tap water HS-SPME:2 g of soil with 400 ml of distilled water 30 at 50 °C Direct SPME: ml stirred sample with 53 ppt of NaCl in the dark for 90 Direct SPME: Sample with g NaCl for 30 Fenitrothion fenitrooxon 3-methyl-4-nitrophenol Monobutyltin dibutyltin tributyltin monophenyltin diphenyltin triphenyltin River water Direct SPME: ml of stirred sample with 15% Na2SO4 60 PDMS/DVB Desorption by dynamic mode during Desorption by dynamic mode during Water HS-SPME: ml stirred sample with ml buffer, ml EtOH and deuterate internal standards, derivatized with 300 μl 1% NaBEt4 sol and extracted at 80 °C for 90 0.5 g sample with ml MeOH and ml acetic acid, placed in ultrasonic bath for h Deuterate internal standard and ml buffer solution were added, derivatized with 500 μL 1% NaBEt4 soln and extracted at 80 °C for 90 Direct SPME: ml of stirred sample with 31% NaCl (w/v) at pH extracted for 150 100 μm PDMS Desorption at 250 °C for – 100 μm PDMS Desorption at 250 °C for 116–98 GC/MS 1–6.3 μg/kg [77] 60 μm PDMS/DVB Desorption with 200 μl MeOH by stirring for 16 and added 200 μl acetic acid 0.4 M before CE injection Desorption at 300 °C for 6.5 5–46 CE/UV 2.5–47 μg/l [75] 64–85% GC/MS 0.6–19 μg/l – [24] 0.02–0.038 μg/l 100 μm PDMS Vinyl crown ether polar fiber: 80 μm B15C5 Desorption at 250 °C for 7.5 Desorption at 270 °C for 76–121 55–105 GC/ECD GC/FPD 0.1–0.5 ng/g 0.003–0.09 ng/g [80] [62] 85 μm PA Desorption at 280 °C for 87–110 GC/MS LOQ 0.004– 0.03 ng/ml [64] 100 μm PDMS Desorption at 240 °C for – GC/NPD 0.05–8.37 μg/l [76] 100 μm PDMS Desorption at 270 °C for 71–121 GC/ECD 0.029– 0.301 ng/g 0.8–13 ng/l 0.8–504 0.09– 143 ng/l 0.02–3.6 ng/g [82] Soil Coastal water Sediments Cyprodinil cyromazine pyrifenox pirimicarb pyrimethanil Water apple and orange juice Aldicarb Carbetamide Propoxur Carbofuran Carbaryl Methiocarb Pirimicarb (7 Carbamates) Organochlorines (8) Organophosphorus (8) Brine water Phenoxy acid herbicides Dicamba (8) Treated urban wastewater Organophosphorus (9) Organochlorines (11) Organophosphorus (11) Fish water potatoes guava coffee Estuarine surface sediments Lake water River water Organochlorines (11) Soil Pesticides (8) Triazine metabolites (3) Organochlorines and metabolites (12) Rain water Radish Organochlorines organophosphorus Pyrethrins (16 pesticides) Pesticides (20) Honey Organochlorines (10) Soil Apple juice Apple Tomato Rain water – Direct SPME: ml sample and ml of water for 120 at 25°C SPE-SPME: 250 ml sample passed through tC-18 SPE cartridge and eluted with ml of MeCN, evaporated and redisolved in ml aqueous solution with 60% (v/v) of brine HS-SPME: 0.5 ml of sample and ml of water are stirred for 60 at 60 °C HS-SPME (Apple juice) 15 ml of diluted juice (1:30) with g NaCl, extracted for 45 at 70 °C Direct SPME: 15 ml apple (1:50) and tomato (1:70) dilution with g NaCl, for 60 at 30 °C Direct SPME: 20 ml stirred Milli-Q water pH 2, HCl 0.1 M extracted for 40 Postderivatization on the fiber exposing it to the headspace of a vial containing 1.5 ml with 50 μl of MBTSTFA for 10 Direct SPME (Solid sample): 0.5 g stirred sample with 16 ml water and for 40 at 30 °C Direct SPME (water): 16 ml sample 40 at 30 °C HS-SPME: 0.5 g stirred sample in ml water and Tween 80, 60 at 70 °C HS-SPME: ml of stirred sample 30 at 80 °C Direct SPME: 10 ml stirred Milli-Q water with 10% NaCl for 45 at 25 °C 85 μm PA PMPVS/OH-TSO 100 μm PDMS Desorption at 270 °C for Desorption at 240 °C for 71–115 71–114 MAE: g sample with 20 ml hexane:acetone (115 °C, 10 min, 200 psi), 15 ml filtered and evaporated to dryness, and redissolved by 720 μl of ethanol and 40 ml of water HS-SPME: 60 65 °C Direct SPME: ml stirred sample 40 50 °C pH and 70% NaCl HS-SPME (water): ml stirred radish matrix solution and g K2SO4 30 at 70 °C Direct SPME: 1.5 g stirred sample with 10 ml phosphate buffer solution at 75 °C for 20 Direct SPME: ml of stirred sample with 50% NaCl, extracted at 40 °C for 45 100 μm PDMS Desorption at 260 °C for 16 8–51 GC/ECD GC/MS GC/ICP/ MS GC/MS/ MS 85 μm PA C[100]/OH-TSO Desorption at 290 °C for Desorption at 270 °C for – 79–119 GC/MS/MS GC/ECD 0.01–0.05 μg/l 1.27–174 ng/kg [71] [78] 100 μm PDMS Desorption at 280 °C for 91 GC/AED 0.02–10 ng/g [67] 100 μm PDMS Desorption at 250 °C for GC/ITD/ MS/MS 5–500 ng/l [65] – [79] [73] [81] M1: 2-methylthio-4-tert-butylamino-6-amino-s-triazine; M2: 3-[4-tert-butylamino-6-methylthiol-s-triazin-2-ylamino]-propionaldehyde; DCAD: Direct current amperometric; MBTSTFA N-methyl-N-(tert-butyldimethylsilyl)-trifluoroacetamide; PMPVS/OH-TSO: poly(methylphenylvinylsiloxane)/hydroxyl-terminated silicone oil;C[4]/OH-TSO : sol/gel calyx[4] arene/hydroxy-terminated silicone oil; AED: atomic-emission detection; MAE: microwave-assisted extraction Y Picó et al / J Biochem Biophys Methods 70 (2007) 117–131 Mean recovery Table In-tube SPME methods for pesticides Matrices Pre-treatment Phenylurea (6) and carbamate (6) pesticides Water and wine Samples extracted with 15 draw/eject cycles 60-cm-long capillary, no buffer solutions or salts were used Characteristics PPY coated on inner surface of a fused-silica capillary (60 cm, 0.25 mm i.d.) Capillary cleaned with acetone and MeOH, dried with N2, and coupled to LC Phenylurea (6) Water and Samples extracted with 15 draw/eject PPY coated on inner surface of a and carbamate wine cycles 60-cm-long capillary, fused-silica capillary (60 cm, 0.25 mm (6) pesticides no buffer solutions or salts were used i.d.) Capillary cleaned with acetone and MeOH, dried with N2, and coupled to LC Carbamates (6) Water Extraction by moving the sample Coated GC capillary (SPB-1, SPB-5, in and out of the extraction capillary PTE-5, Supelcowax, Omegawax 250) (25 aspirate/dispense steps at a and retention gap capillary flow-rate of 63 μl/min) (fused-silica without coating) were used in the in-tube SPME PC-HFME Polymer-coated Water 1.2 cm of fiber, coated with g/l of Organochlorine PH-PPP in toluene Extraction at 23 °C hollow fiber 600 μm of i.d., pesticides for 30 in 30% NaCl and at pH 10 200 μm wall; 0.2 μm pore size (15 OCP) HFM-SPME Polypropylene 65 μm PDMS/DVB fiber Extraction Triazine herbicides Bovine milk hollow fiber 600 μm (i.d.), at 80 °C for 40 in 30% NaCl (6 triazines) and sewage 200 μm wall; 0.2 μm pore size sludge samples and at pH 10 Elution Recovery (%) Detection LOD (ng/l) LOQ (ng/l) Reference SPME, coupled 95–104 (water) automated in-tube to 89–97 (wine) LC desorption with mobile phases LC/UV – [86] 95–104 (water) SPME, coupled automated in-tube to 89–97 (wine) LC desorption with mobile phases L C / E S I / 10–1200 MS – [86] Desorption in-tube SPME procedure with MeOH 97–100 LC/UV 1000– 15,000 – [87] Sonication with hexane for 10 85–106 GC/MS 1–8 – [89] Desorptions in splitless mode 88–107 (milk) GC/MS 93–113 (sludge) 380–8200 3–13 (milk) 6–21 (milk) – [88] 1–9 (sludge) (sludge) Y Picó et al / J Biochem Biophys Methods 70 (2007) 117–131 Analytes i.d.: inner diameter; HF: hollow fiber; HFM: hollow-fiber membrane; PC-HFME: polymer-coated hollow-fiber micro-extraction; HFM-SPME: hollow-fiber membrane protected solid phase-micro-extraction; FTD: flame-thermoionic detector; PH-PPP: polyhydroxylated polyparaphenylene; PDMS/DVB: polydimethylsiloxane/divinylbenzene; PPY: polypyrrole; PMPY: poly-N-methylpyrrole 125 126 Table MSPD methods for pesticides Analyte Matrices Pre-treatment Characteristics Elution Recovery (%) Detection LOD's LOQ's (μg/kg) (mg/kg) Carbamate (1), organophosphate (3), organochlorine (1), imidazole (1), triazole (2), insecticide growth regulator (1), mouse growth regulator (1) Insecticide growth regulators (3), pyrimidine insecticide (1), pyrazole insecticide (1) and pyrethroid insecticide Oranges Unwashed and unpeeled samples were chopped and homogenized for at high speed 0.5 g of C8 bonded silica Elution was made with DCM/MeOH (80:20, v/v) and vacuum Eluate was concentrated to 0.5 ml MeOH 47–96 LC/MS – Unwashed and unpeeled samples were chopped and homogenized Sample was blended with C18 bonded silica for 0.5 g of C18 bonded silica Elution was made with DCM/MeOH (80:20, v/v) and vacuum Eluate was concentrated to 0.5 ml MeOH 51–92 LC/MS/ MS 5–1000 0.2–4 (μg/l) Organochlorine pesticides (18) Citrus fruit (oranges, tangerines, grape fruits and lemons) Tobacco g of pretreated and deactivated Florisil Extract was concentrated to 1.0 mL 52–99 GC/ECD – – [100] 0.02 Pesticides (226) Apple juice 43–117 GC/MS 3–18 – Organophosphates (3), organochlorines (3), pyrethroids (2), triazines (3), urea (1) Glyphosate and aminomethylphosphonic acid (AMPA) Olive and olive oil MSPD-SSEC Florisil was heated at 550 °C overnight and homogenized in water in a rotary evaporator for h Samples were extracted in Soxhlet with heat n-hexane for h Juice was homogenized with diatomaceous earth Sample was blended with C18 bonded silica for before MSPD procedure samples were kept for h in darkness at °C Preliminary LLE in olive oil samples with petroleum ether saturated with MeCN Separation of MeCN phase and applying MSPD Two aqueous samples were obtained after MSPD homogenized Clean-up with SAX anion exchange silica 81–111 (LC–MS) 73–130 (GC–MS) 86–93 GC/MS; LC/MS/ MS 0.2–80 – [92] LC/FD 30–50 – [102] Organochlorine (11), pyretroids (5) Tea GC/ ECD; GC/MS LC/ESI/ MS/MS – 0 – [98] 0.06 0.03 (μg/l) 0.1 (μg/l) Homogeneous mixture (sample and Florisil) was transferred in a glass cartridge, connected to vacuum and eluted Juice was adjusted a pH and sonified in Fruit juice ultrasonic bath for 15 before MSPD (apple, peach, cherry, raspberry, procedure and orange) g of diatomaceous earth DCM 80–96 82–102 SSEC:Soxhlet simultaneous extraction clean-up; LLE: liquid/liquid extraction; FD: fluorescence detection; FMOC-Cl: 9-fluorenylmethylchloroformate; DCM: dichloromethane 0 – [91] 0.3 [93] [101] [103] Y Picó et al / J Biochem Biophys Methods 70 (2007) 117–131 Carbendazim Tomato fruit Elution was made with DCM/MeOH (1/1) and evaporated to dryness in a rotary vacuum Eluate was concentrated to ml Elution with MeCN, evaporated Aminopropyl (Bondesil-NH2, until dryness and dissolved with 40 μm particle MeCN/water (1:1) Clean-up step size) with Florisil HNO3 M and Elution with HNO3 0.01 M NH2-silica extract were evaporated at 40 °C and pH adjusted to 7–9 for the derivatization reaction with FMOC-Cl 2.0 g Florisil n-hexane/DCM (1:1, v/v) 20 g of diatomaceous earth Reference Table SBSE methods for pesticides Matrices Pre-treatment Characteristics Elution Carbamate (1), organophosphates (3), organochlorine (1), imidazole (1), triazoles (2), insecticide growth regulator (1), mouse growth regulator (1) Azole (1), insect growth regulation (1), pyrethroid (1), pyrrole (1), triazole (4) Oranges Samples homogenized with MeOH and water by sonication for 15 min, filtered and washed with water and extracted with stir bar for h Stir bar was filled with MeCN and conditioned with MeCN for by sonication Samples were homogenized with acetone and water by sonication for 15 min, filtered and washed with acetone and extracted with stir bar for h at 900 rpm Stir bar was filled and conditioned with MeOH for by sonication Extraction with n-tetradecane, stirring speed of 600 rpm for 30 at 25 °C Stir bar, 10 mm in length and coated with a 1-mm PDMS layer Desorption with MeCN in an ultrasonic device for 10 8–84 Stir bar, 10 mm in length and coated with a 1-mm PDMS layer Desorption with MeOH, concentrated to dryness and redissolved with 0.5 ml of buffer 12–47 SBME/HFM impregnated with n-tetradecane The ends of the fiber were sealed, forming a bar that extracts pesticide by a magnetic stirrer 20 mm long PDMS stir bar 93–101 Organic extracting solvent is withdrawn into a micro-syringe for injection into the gas chromatograph TSD at 280 °C – for Organochlorine pesticides (6) Fruits and vegetables Wine Organochlorine pesticides (17), Tap water, ground organophosphorus water and surface water pesticides (4), triazines (8) Organophosphorus pesticides (12) Pesticides (68) Pesticides (85) Pyrethroid pesticides (8) Samples were added with 20% NaCl Stir bar at 900 rpm for 14 h at ambient temperature Na2S2O3·5H2O was added to tap water to eliminate chlorine stir bar conditioned in a thermodesorption tube at 300 °C for h with He flow Water, cucumber, potato Samples were immersed for 30 with stirring at 600 rpm at 30 °C with 30% NaCl Vegetable samples were extracted with acetone prior to SBSE Extracts were concentrated at ml and diluted to 20 ml with water River water Samples were added with 30% NaCl Stir bar was stirred at 1000 rpm for 60 at room temperature Samples were extracted with Grape, tomato, cucumber, green beans, soybeans, spinach, MeOH and diluted with water prior to SBSE green tea SBSE performed at 24 °C, for 60 min., stirring at 1000 rpm Stir bar thermally conditioned at 300 °C for 30 with He flow Water SBSE performed with 5% MeOH as organic modifier, at 20 °C for 60 stirring at 750 rpm, and MeCN as back-extraction solvent 10-mm stir bar, coated with PDMS Dual SBSE Stir bar coated with PDMS Reference – 0.001–0.05 [91] CE – [97] GC/MS/ MS 0.3–17.3 – [104] GC/MS 0.1–10.7 0.4–36.1 (ng/l) [105] – GC/TSD 0.06–1.22 (water) – 4–15 (ng/kg; cucumber) 1.2–98 (ng/kg; potato) [96] TSD by programming from 20 °C (0.5 min) to 300 °C (5 min.) TSD by programming from 20 °C (1 min.) to 280 °C (5 min.) 59–132 GC/MS 0.2–2 [106] – GC/MS 0.63–26 (μg/kg) – LD with MeCN 67–103 GC/MS 1–2.5 3–7.5 (ng/l) [108] [107] 127 PDMS: polydimethylsiloxane; ACN: acetonitrile; CE: capillary electrophoresis; TSD: Thermal desorption; LD: liquid desorption LOQ's (mg/kg) LC/MS A sol/gel PDMS was used to TSD at 260 °C coated bars consisting of an iron for bar inside a glass tube Stir bar coated with PDMS Recovery Detection LOD's (%) (ng/l) Y Picó et al / J Biochem Biophys Methods 70 (2007) 117–131 Analyte 128 Y Picó et al / J Biochem Biophys Methods 70 (2007) 117–131 Fig LC/MS chromatograms of an orange sample containing 0.02 mg/kg carbendazim, 0.07 mg/kg hexythiazox, 0.1 mg/kg methidathion, and 0.07 mg/kg pyriproxyfen after (A) ethyl acetate extraction (B) SBSE, and (C) MSPD Peak identification: = carbendazim, = methidathion, = pyriproxyfen, 10 = hexythiazox (from Blasco et al [91]) Typical chromatograms of organophosphorus pesticides in standard solution and a spiked cucumber sample, obtained by SBSE/GC/TSD, are shown in Fig Applications Selecting a suitable method of residue analysis will depend on the problem at hand as well as on the final goal To quote two widely different situations, when large sample series have to be monitored for a group of pesticides, such as organophosphorus pesticides, sample throughput will be an important criterion since speed is of the essence In this situation, a screening method is selected, because high sample throughput and speed are the characteristics of such a method When, on the other hand, samples are suspected to contain a prohibited pesticide, such as, e.g., methylparathion in oranges, method selectivity will no doubt be the main criterion, because avoiding false noncompliant results is now of overriding importance In this situation, a confirmatory method is of interest, because it provides full or complementary information, enabling confirmation of the identity of the substance Here our discussion will be limited to method selection and a few comments on SPE that can be considered relevant in light of recent trends in pesticide residue analysis The applications of the different SPE methods since 2003 for pesticide residues in food and environmental analysis are compiled in Table (SPE methods), Table (SPME methods), Table (in-tube SPME methods), Table (MSPD methods), and Table (SBSE methods) An evaluation of the scientific literature of the years 2003–2006 shows that some 100 papers on pesticide/ drug residue analysis have been published With regard to sample treatment, SPE and SPME were found to be very popular, being used in, respectively, 17 and 25% of all studies The application of MSPD, in-tube SPME, and SBSE is reported in only a few papers In several instances, SPE and SPME were used in combination: after analyte isolation by means of SPE, the pesticides were enriched by using a suitable SPME procedure Fig displays the LC/MS chromatogram of an orange sample, extracted by different procedures: solvent extraction (ethyl acetate), MSPD, and SBSE This figure shows differences in sensitivity between the three extraction methods as well as the absence of a carbendazim signal when SBSE was used [96] Y Picó et al / J Biochem Biophys Methods 70 (2007) 117–131 Conclusions Comparison of the above procedures applied to the SPE of pesticide residues indicates: • Conventional off- and on-line SPE is already a wellestablished and routine technique • SPME and SBSE in combination with GC/MS or LC are solvent-free or almost solvent-free procedures, obviating the need for further preparation steps • One advantage of SPME is the possibility of full automation; SBSE cannot yet be completely automated • SPME is now a widely accepted and reliable technique for the determination of several organic compounds In the headspace mode, it allows attainment of satisfactory LODs and cleaner chromatograms for volatile analytes • SPME has been widely used in recent years, 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stir-bar-sorptive extractionliquid desorption-large-volume injection capillary gas chromatographic– mass spectrometric method for pyrethroid pesticides in water samples Anal Bioanal Chem 2005;382:1141–51  ... can integrate sampling, extraction, pre-concentration, and sample introduction into a single uninterrupted process resulting in high sample throughput A large number of fiber coatings based on solid. .. is given for SPE, SPME, in- tube SPME, MSPD, and SBSE methods Solid- phase- based extraction techniques 2.1 Solid- phase extraction The SPE technique was first introduced in the mid-1970s [16] It... pesticide determination in drinking water The use of fully automated on-line RP–LC/GC has also been reported, mainly for the determination of pesticide residues in olive oil This procedure, in conjunction