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[.]

Current trends in solid-phase-based extraction techniques for the

determination of pesticides in food and environment

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

1 Introduction 117

2 Solid-phase-based extraction techniques 118

2.1 Solid-phase extraction 118

2.2 Solid-phase micro-extraction 119

2.3 In-tube solid-phase micro-extraction 121

2.4 Matrix solid-phase dispersion 121

2.5 Stir-bar sorptive extraction 122

3 Applications 128

4 Conclusions 129

Acknowledgments 129

References 129

1 Introduction

The analysis of pesticide residues in food and environmental

samples has received increasing attention in the last few

de-cades, as can be deduced from the great number of papers

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

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

J Biochem Biophys Methods 70 (2007) 117 – 131

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⁎ Corresponding author Tel.: +34 96 3544295; fax: +34 96 3544954

E-mail address:guillermina.font@uv.es(G Font)

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doi:10.1016/j.jbbm.2006.10.010

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

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

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

pesti-cides 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

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)

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-phase-based 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] More-over, 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 proce-dures developed to isolate and pre-concentrate pesticide resi-dues as well as the principles and relative merits of each procedure are summarized and discussed Isolation and pre-treatment 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.

2 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 Con-ventional 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 1 GC/MS chromatogram of pesticide-spiked lemon essential oil (from Barrek et al.[43])

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

carbohy-drates 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

im-munosorbents [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

car-ried 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

N-methylcarbamates and their metabolites in soil and food [61]

sample of lemon essential oil, previously extracted with a

Florisil cartridge The temperature ramp is an important step,

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 co-workers and has been marketed by Supelco since 1993 Sub-sequently, 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(acri-late) (PA) coated fibers, namely: PDMS/divinylbenzene (DVB), Carbowax/DVB, Carbowax/template resin (TR), Carboxen/ PDMS, and DVB/Carboxen/PDMS-coated fibers Extraction of

Fig 2 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 1 = 100 ng/g chlordimeform, 2 = 150 ng/g dimethoate, 3 = 2 ng/g aldrin, 4 = 20 ng/g parathion-ethyl, 5 = 80 ng/g captan,

6 = 20 ng/g chlorfenvinphos, 7 = 3 ng/g dieldrin, 8 = 2 ng/g p,p'-DDE, 9 = 0.5 ng/g p,p'-DDD, 10 = 1 ng/g p,p'-DDT, 11 = 10 ng/g bromopropylate, 12 =

3 ng/g tetradifon, 13 = 60 ng/g azinphos-methyl, 14 = 20 ng/g λ-cyalothrin, 15 =

5 ng/g cumaphos, 16 = 100 ng/g deltamethrin (from Campillo et al.[67])

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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

char-acteristics 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, do 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

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 satisfac-tory quantification of the analytes [66,69,70,83]

Fig 3 Chromatogram obtained by using a proposed procedure for the new SPME fiber on the spiked samples of 10 ng ml− 1of each organophosphorus pesticide (A) water and (B) apple juice Peak identification: 1 = dichlorvos, 2 = phorate, 3 = diazinon, 4 = methyl parathion, 5 = fenitrotion, 6 = malathion, 7 = parathion, 8 = ethion (from Linghsuang et al.[62])

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 2 illustrates the elution profiles

obtained at different channels from fortified honey, using a

non-polar (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 3

shows the chromatogram of apple juice compared with that of

pure water containing the same concentration of

organophos-phorus 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

pre-concentration technique, which can be easily coupled on-line

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 injec-tion with an autosampler, is commonly used in combinainjec-tion 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 disper-sion 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 size-exclusion 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 4 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])

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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 stir-bar sorptive extraction (SBSE), a magnetic stir 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 5 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 1 = monocrotophos, 2 = phorate, 3 = dimethoate, 4 = parathion-methyl, 5 = malathion, 6 = fenitrothion, 7 = fenthion, 8 = chlorpyrifos, 9 = parathion, 10 = methidathion, 11 = triazophos, 12 = ethion (from Liu et al.[96])

SPE methods for pesticides

Analyte Matrices Pre-treatment Characteristics Elution Recovery (%) Detection LOD's (μg/l) LOQ's (mg/kg) Reference Azole (1), insect growth

regulator (1), pyrethroid (1),

pyrrole (1), triazole (4)

Fruits and vegetables Aqueous sample extract passed through

the C 18 column

MFE C 18 solid phase (45- to 55-μm particle diameter and 60 Å pore diameter)

Pesticides eluted with DCM.

Concentrated to dryness and redisolved

in 0.5 ml of buffer

31–106 CE – 0.2–0.5 [97]

Azole (1), insect growth

regulator (1), pyrethroid (1),

pyrrole (1), triazole (4)

Peach and nectarine Samples homogenized with water:MeCN

(50:50) for 15 min acetone was evaporated.

Extract passed through the C 18 column

C 18 solid phase Pesticides eluted with DCM.

Concentrated to dryness and redisolved in 0.5 ml of buffer

58–99 CE/MS 50–200 (CE–MS) – [40]

Carbamates (7) Water Samples passed through tC 18 cartridge Sep-Pak tC 18 cartridges Carbamates eluted with 2 ml MeCN.

Concentrated to dryness and redisolved in 0.5 ml of MeCN

64–85 GC/MS 0.02–0.038 – [24]

Triazines (6) and metabolites (5) River and tap water 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

Selective MIP cartridges for triazines and related metabolites Metabolites extracted by SPE with a mixture of propazine-MIP and LiChrolut EN

Triazines eluted with MeCN:acetic acid (9:1).

Concentrated to dryness and redisolved

in 0.5 ml of water: MeCN (9:1)

7–91 LC/DAD UV 0.03–0.2 – [25]

Organochlorine pesticides (13) Surface water Water samples containing 1% MeCN were

pre-concentrated through C 18 E cartridges

Strata C 18 E cartridges 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

72–119 LC/MS/MS 0.0008–

0.083

– [26]

Neonicotinoid pesticides (4) Apricot, celery,

courgette, peach, pear

Samples homogenized with acetone for

2 min in mixer at 9500 rpm

Extrelut-NT20 cartridge Pesticides eluted with DCM.

Evaporated at 40 °C under vacuum and redissolved in 1 ml of MeOH

75–105 LC/ESI/MS – 0.1–0.5 [41]

Triazolopyrimidine pesticides (5) Soils Soil samples extracted with water and

0.1 M NaOH in ultrasonic bath for 20 min.

Centrifuged at 4000 rpm for 10 min to separate the supernatant Added HCl and passed to C 18 SPE cartridge

Sep-Pak Plus C 18 cartridges Pesticides eluted with MeCN Evaporated

to dryness under vacuum and redissolved

in 1 ml MECN and 200 μl of 16 mM ammonium carbonate solution

50–84 CE/UV 18–34 (μg/kg) – [42]

Triazolopyrimidine

pesticides (5)

Water Water samples containing hydrochloric

acid were pre-concentrated through C 18

SPE cartridges

Sep-Pak Plus C 18 cartridges Pesticides eluted with MeCN.

Evaporated to dryness at 40 °C and redissolved in 1 ml MeCN

55–110 CE/UV 0.13–0.34 – [27]

Organochlorines (11),

pyretroids (5)

Tea Samples extracted by vortex gyrator a full speed

for 2 min Centrifuged at 3000 rpm for 5 min.

Supernatant layers were extracted

Florisil column preconditioned with n-hexane

n-hexane:DCM (1:1, v/v), concentrated

to dryness and redissolved in 0.5 ml n-hexane

69–96 GC/ECD;

GC/MS

– 0.004–0.09 [98]

Pesticides (12) Oils of citrus fruit Samples homogenized in an ultrasonic bath for

15 min Extract passed through a Florisil cartridge

FL-PR extraction cartridge Pesticides eluted with DCM.

Extracts concentrated at 30 °C

67–107 GC/MS 30–400 – [43]

Pesticides (12) Oils of citrus fruit Samples homogenized in an ultrasonic bath for

15 min Extract passed through a Florisil cartridge

FL-PR extraction cartridge Pesticides eluted with DCM.

Extracts concentrated at 30 °C.

50–115 LC/MS 20–60 – [43]

Organochlorine pesticides Drinking water Samples passed through C 18 cartridge SPE-LVI Pesticides desorbed with 0.5 ml

of ethyl acetate.

– GC/MS 10–50 (ng/l) 33–166

(ng/l)

[28]

Urea (3), 2,4-D and amitrine Water Samples passed through C 18 cartridge 1.0 g C 18 bonded silica phase MeCN 98–104 LC/UV 10–30 35–100 (μg/l) [29]

Triazines (6) Water Samples passed through C 18 cartridge Backerbond SPE C-18 polar MeOH 88–95 TLC plates 10 30 (μg/l) [30]

Triazines, phenylureas,

organophosphorus, anilines,

acidic, propnil, molinate

Water None On-line trace enrichment Mobile phase of LC – LC/ESI–

MS/MS

0.011–7.4 (ng/l) 0.004–2.8 (ng/l) [31]

Organophosphorus (4) Olives Filtering of the olive oil LC/GC on-line LC

column C4,Chromasil

MeOH/water – GC/FID 0.18–0.38 mg/l [44]

Benzoylureas (5) Water Filtering C-18 short column Mobile phase

(MeOH/water gradient program)

92–109 LC/

Fluorescence

0.01–0.02 (μg/l) 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.

Table 2

SPME methods for pesticides

Analyte Matrices Pre-treatment Characteristics Elution Mean

recovery Detection LOD Reference Molinate Rice field and

water

Direct SPME: 5 ml stirred sample with 200 g/l sodium sulfate and internal standard for 30 min.

DVB/CAR/PDMS Desorption at 220 °C for 5 min 79–97 GC/FPD 0.48–5.2 μg/l [70]

Fenbutatin oxide Water HS-SPME: 5 ml sample with 5 ml HOAc/NaOAc buffer

and internal standard solution added In situ derivation with

300 μl of 1% NaBEt 4 sol Vigorously shaken in ultrasonic bath for 10 min and extracted for 30 min at 80 °C

100 μm PDMS Desorption at 250 °C for 1 min. – GC/MS 16 ng/l [99]

1,3-dichloropropene

methyl isothiocyanate

Water Direct SPME: 3 ml stirred sample with 30% NaCl 30 min at 25 °C 85 μm PA Desorption at 175 °C for 5 min. – GC/ECD/

NPD

0.5 μg/l [66]

1,3-dichloropropene

methyl isothiocyanate

Soil HS-SPME:2 g of soil with 400 ml of distilled

water 30 min at 50 °C

85 μm PA Desorption at 175 °C for 5 min. – GC/ECD/

NPD

0.001 mg/kg [66]

Irganrol-1051 related s-triazine

degradation products (M1 and M2)

Coastal water Direct SPME: 5 ml stirred sample with 53 ppt of NaCl

in the dark for 90 min.

100 μm PDMS Desorption at 240 °C for 5 min – GC/MS

GC/FID

20–100 ng/l [68]

Nabam thiram azamethiphos Tap water Direct SPME: Sample with 5 g NaCl for 30 min 100 μm PDMS Desorption by dynamic mode during

5 min.

– LC/UV (254 nm)

1–10 ng/ml [69]

Fenitrothion fenitrooxon

3-methyl-4-nitrophenol

River water Direct SPME: 3 ml of stirred sample with 15% Na 2 SO 4 60 min PDMS/DVB Desorption by dynamic mode during 5 min – LC/DAD

LC/DCAD

1.2–11.8 μg/l [83]

Monobutyltin dibutyltin

tributyltin monophenyltin

diphenyltin triphenyltin

Water HS-SPME: 5 ml stirred sample with 5 ml buffer,

1 ml EtOH and 6 deuterate internal standards, derivatized with 300 μl 1% NaBEt 4 sol and extracted at 80 °C for 90 min.

100 μm PDMS Desorption at 250 °C for 1 min – GC/MS 1.3–15 ng/l [77]

Sediments 0.5 g sample with 1 ml MeOH and 1 ml acetic acid,

placed in ultrasonic bath for 3 h Deuterate internal standard and 8 ml buffer solution were added, derivatized with 500 μL 1% NaBEt 4 soln and extracted at 80 °C for 90 min.

100 μm PDMS Desorption at 250 °C for 1 min 116–98 GC/MS 1–6.3 μg/kg [77]

Cyprodinil cyromazine pyrifenox

pirimicarb pyrimethanil

Water apple and orange juice

Direct SPME: 6 ml of stirred sample with 31% NaCl (w/v)

at pH 6 extracted for 150 min.

60 μm PDMS/DVB Desorption with 200 μl MeOH by stirring

for 16 min and added 200 μl acetic acid 0.4 M before CE injection

5–46 CE/UV 2.5–47 μg/l [75]

Aldicarb Carbetamide Propoxur

Carbofuran Carbaryl Methiocarb

Pirimicarb (7 Carbamates)

Brine water Direct SPME: 6 ml sample and 4 ml of water for 120 min at 25°C SPE-SPME:

250 ml sample passed through tC-18 SPE cartridge and eluted with 2 ml

of MeCN, evaporated and redisolved in 8 ml aqueous solution with 60% (v/v) of brine

85 μm PA Desorption at 300 °C for 6.5 min 64–85% GC/MS 0.6–19 μg/l –

0.02–0.038 μg/l

[24]

Organochlorines (8) Soil HS-SPME: 0.5 ml of sample and 5 ml of water are stirred for 60 min at 60 °C 100 μm PDMS Desorption at 250 °C for 7.5 min 76–121 GC/ECD 0.1–0.5 ng/g [80]

Organophosphorus (8) Apple juice

Apple Tomato

HS-SPME (Apple juice) 15 ml of diluted juice (1:30) with 5 g NaCl, extracted for 45 min at 70 °C Direct SPME: 15 ml apple (1:50) and tomato (1:70) dilution with 5 g NaCl, for 60 min at 30 °C

Vinyl crown ether polar fiber:

80 μm B15C5

Desorption at 270 °C for 5 min 55–105 GC/FPD 0.003–0.09

ng/g

[62]

Phenoxy acid herbicides Dicamba (8) Treated urban

wastewater

Direct SPME: 20 ml stirred Milli-Q water pH 2, HCl 0.1 M extracted for 40 min Postderivatization on the fiber exposing it to the headspace of a vial containing 1.5 ml with 50 μl of MBTSTFA for 10 min.

85 μm PA Desorption at 280 °C for 3 min 87–110 GC/MS LOQ 0.004–

0.03 ng/ml

[64]

Organophosphorus (9) Fish water

potatoes guava coffee

Direct SPME (Solid sample): 0.5 g stirred sample with

16 ml water and for 40 min at 30 °C Direct SPME (water):

16 ml sample 40 min at 30 °C

100 μm PDMS Desorption at 240 °C for 5 min – GC/NPD 0.05–8.37 μg/l [76]

Organochlorines (10) Estuarine surface

sediments

HS-SPME: 0.5 g stirred sample in 5 ml water and Tween 80,

60 min at 70 °C.

100 μm PDMS Desorption at 270 °C for 5 min 71–121 GC/ECD 0.029–

0.301 ng/g

[82]

Organochlorines (11) Lake water HS-SPME: 4 ml of stirred sample 30 min at 80 °C PMPVS/OH-TSO Desorption at 270 °C for 2 min 71–115 GC/ECD 0.8–13 ng/l [79]

Organophosphorus (11) River water Direct SPME: 10 ml stirred Milli-Q water with 10% NaCl for 45 min at 25 °C 100 μm PDMS Desorption at 240 °C for 5 min 71–114 GC/MS

GC/ICP/ MS

0.8–504 0.09–

143 ng/l

[73]

Organochlorines (11) Soil MAE: 5 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 min 65 °C.

100 μm PDMS Desorption at 260 °C for 16 min 8–51 GC/MS/ MS 0.02–3.6 ng/g [81]

Pesticides (8) Triazine metabolites (3) Rain water Direct SPME: 3 ml stirred sample 40 min 50 °C pH 6 and 70% NaCl 85 μm PA Desorption at 290 °C for 5 min – GC/MS/MS 0.01–0.05 μg/l [71]

Organochlorines and metabolites (12) Radish HS-SPME (water): 4 ml stirred radish matrix solution and

1 g K 2 SO 4 30 min at 70 °C

C[100]/OH-TSO Desorption at 270 °C for 2 min 79–119 GC/ECD 1.27–174 ng/kg [78]

Organochlorines organophosphorus

Pyrethrins (16 pesticides)

Honey Direct SPME: 1.5 g stirred sample with 10 ml phosphate buffer

solution at 75 °C for 20 min

100 μm PDMS Desorption at 280 °C for 5 min 91 GC/AED 0.02–10 ng/g [67]

Pesticides (20) Rain water Direct SPME: 3 ml of stirred sample with 50% NaCl, extracted

at 40 °C for 45 min.

100 μm PDMS Desorption at 250 °C for 5 min. – GC/ITD/

MS/MS

5–500 ng/l [65]

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(methylphenylvi-nylsiloxane)/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.

Table 3

In-tube SPME methods for pesticides

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

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

SPME, coupled automated in-tube to

LC desorption with mobile phases

95–104 (water) 89–97 (wine)

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

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

SPME, coupled automated in-tube to

LC desorption with mobile phases

95–104 (water) 89–97 (wine)

L C / E S I / MS

Carbamates (6) Water Extraction by moving the sample

in and out of the extraction capillary (25 aspirate/dispense steps at a flow-rate of 63 μl/min)

Coated GC capillary (SPB-1, SPB-5, PTE-5, Supelcowax, Omegawax 250) and retention gap capillary

(fused-silica without coating) were used in the in-tube SPME

Desorption in-tube SPME procedure with MeOH

15,000

Organochlorine

pesticides

(15 OCP)

Water 1.2 cm of fiber, coated with 1 g/l of

PH-PPP in toluene Extraction at 23 °C for 30 min in 30% NaCl and at pH 10

PC-HFME Polymer-coated hollow fiber 600 μm of i.d.,

200 μm wall; 0.2 μm pore size

Sonication with hexane for 10 min

Triazine herbicides

(6 triazines)

Bovine milk and sewage sludge samples

65 μm PDMS/DVB fiber Extraction

at 80 °C for 40 min in 30% NaCl and at pH 10

HFM-SPME Polypropylene hollow fiber 600 μm (i.d.),

200 μm wall; 0.2 μm pore size

Desorptions in splitless mode

88–107 (milk) 93–113 (sludge)

GC/MS 3–13 (milk)

1–9 (sludge)

6–21 (milk) – (sludge)

[88]

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

Table 4

MSPD methods for pesticides

(%)

Detection LOD's

(μg/kg)

LOQ's (mg/kg)

Reference

Carbamate (1), organophosphate (3),

organochlorine (1), imidazole (1),

triazole (2), insecticide growth

regulator (1), mouse growth

regulator (1)

Oranges Unwashed and unpeeled samples

were chopped and homogenized for 3 min 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

0.3

[91]

Insecticide growth regulators (3),

pyrimidine insecticide (1),

pyrazole insecticide (1) and 1

pyrethroid insecticide

Citrus fruit (oranges, tangerines, grape fruits and lemons)

Unwashed and unpeeled samples were chopped and homogenized

Sample was blended with C18 bonded silica for 5 min

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

MS

5–1000 (μg/l) 0.2–4 [93]

Organochlorine pesticides (18) Tobacco MSPD-SSEC Florisil was heated at

550 °C overnight and homogenized

in water in a rotary evaporator for 1 h

Samples were extracted in Soxhlet with heat n-hexane for 6 h

5 g of pre-treated and deactivated Florisil

Extract was concentrated to 1.0 mL

0.02

[100]

earth Sample was blended with C18bonded silica for 5 min before MSPD procedure samples were kept for 3 h in darkness at 4 °C

20 g of diatomaceous earth

Elution was made with DCM/MeOH (1/1) and evaporated

to dryness in a rotary vacuum

Eluate was concentrated to 1 ml

Organophosphates (3),

organochlorines (3),

pyrethroids (2),

triazines (3), urea (1)

Olive and olive oil

Preliminary LLE in olive oil samples with petroleum ether saturated with MeCN

Separation of MeCN phase and applying MSPD

Aminopropyl (Bondesil-NH2,

40 μm particle size)

Elution with MeCN, evaporated until dryness and dissolved with MeCN/water (1:1) Clean-up step with Florisil

81–111 (LC–MS) 73–130 (GC–MS)

GC/MS;

LC/MS/

MS

Glyphosate and

aminomethylphosphonic

acid (AMPA)

Tomato fruit Two aqueous samples were obtained

after MSPD homogenized

Clean-up with SAX anion exchange silica

HNO31 M and

NH2-silica

Elution with HNO30.01 M extract were evaporated at 40 °C and pH adjusted to 7–9 for the derivatization reaction with FMOC-Cl

Organochlorine (11), pyretroids (5) Tea Homogeneous mixture (sample and

Florisil) was transferred in a glass cartridge, connected to vacuum and eluted

ECD;

GC/MS

– 0 0 0 5 – 0.06

[98]

(apple, peach, cherry, raspberry, and orange)

Juice was adjusted a pH 6 and sonified in ultrasonic bath for 15 min before MSPD procedure

1 g of diatomaceous earth

MS/MS

0.03 (μg/l)

0.1 (μg/l)

[103]

SSEC:Soxhlet simultaneous extraction clean-up; LLE: liquid/liquid extraction; FD: fluorescence detection; FMOC-Cl: 9-fluorenylmethylchloroformate; DCM: dichloromethane