Development of dispersive liquid–liquid microextraction method for the analysis of organophosphorus pesticides in tea

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<ul><li><p>Journal of Hazardous Materials 169 (2009) 907911</p><p>Contents lists available at ScienceDirect</p><p>Journal of Hazardous Materials</p><p>journa l homepage: www.e lsev ier .com</p><p>Develo exthe ana te</p><p>Soleymaa Department o , Tehrab Electroanalyt</p><p>a r t i c l</p><p>Article history:Received 2 FebReceived in reAccepted 8 ApAvailable onlin</p><p>Keywords:OrganophosphGC-FPDTea sample anDispersive liqu</p><p>deterliquxturempleter; trform3 andetwe</p><p>g/kg fosedlow c</p><p>1. Introduction</p><p>Pesticides including organochlorine pesticides (OCPs), organo-phosphorusare types opesticides pbut by bioaally becomeof their highhealth, OCPdeveloped cin many coronment mmost toxic pwater, fruitconsumed ttherapeuticals used forpesticides uble risks toin the worlimportant s</p><p> Corresponistry, Iran Univfax: +98 21 77</p><p>E-mail add</p><p>countries have set their own maximum residue limits (MRLs) ofpesticides for tea and other plants consumed as infusions. Thus,for example, the European Community legislation established the</p><p>0304-3894/$ doi:10.1016/j.jpesticides (OPPs), and nitrogen-containing herbicidesf well-known environmental contaminants. The use ofrovides benets for increasing agricultural production,ccumulation through the food web they can eventu-a risk or threat to both animals and humans. Becausely persistent properties and potential threat to human</p><p>s have been prohibited to be produced and used in mostountries. Instead OPPs are used as a substitute for OCPsuntries nowadays because they can degrade the envi-ore easily [1]. Although OPPs as a whole are not theollutants, they can be traced in a wide range of surface</p><p>, vegetable and foodstuff [2]. Many types of plants arehroughout the world as infusions for both pleasure andpurposes. Like other agricultural products, the materi-infusions must be subjected to control because of thesed for their cultivation, in order to minimise possi-human health. Tea is one of the most popular drinksd, so that such water-based drinks could represent anhare of total human exposure to pesticides [3]. Several</p><p>ding author at: Department of Analytical Chemistry, Faculty of Chem-ersity of Science and Technology, Tehran, Iran. Tel.: +98 21 73912750;491204.ress: (M.-R.M. Hosseini).</p><p>MRLs for the pesticides considered in the present study at between0.02g/g for tetradifon and 5g/g for deltamethrin [4] in a widevariety of vegetables, although no MRL is specied in the case ofothers such as coumaphos. Different analytical procedures wereused for the determination of pesticides in medicinal plants andtea [3,511]. Owing to low concentration, the compounds of inter-est have to be separated from the matrix and concentrated to reachthe minimum level required for the particular detector used. Solid-phase extraction (SPE) [12], liquidliquid extraction (LLE) [13], stirbar sorptive extraction (SBSE) [14] and solid-phasemicroextraction(SPME) [11,15] have been used for the separation and preconcentra-tionofpesticides fromthe infusionmatrices.Actually, thereareonlyfew studies based on modern sample preparation methods such asSPME, SBSE (stirring bar sorptive extraction) and SFE (supercriticaluid extraction) focusing on the determination of pesticides in phy-tomedicines (herbal drugs, infusions, tinctures, dried extracts, etc.)[8,9,11,1416]. Plant infusions are complex samples, containing sev-eral endogenous compounds extracted from the leaves by the hotwater during their preparation. Also, it is possible to nd a widerange of different pesticide residues on these infusions, depend-ing on the precedence of a particular sample; when present, theseanalytes are usually found on extremely low levels (g/L or less).</p><p>Therefore, the procedures for the chromatographic detectionand quantitation of organochlorine (OCP) and organophosphorus(OPP) on Passiora infusionsmust incorporate selective, robust and</p><p>see front matter 2009 Elsevier B.V. All rights reserved.hazmat.2009.04.030pment of dispersive liquidliquid microlysis of organophosphorus pesticides in</p><p>n Moinfara, Mohammad-Reza Milani Hosseinia,b,</p><p>f Analytical Chemistry, Faculty of Chemistry, Iran University of Science and Technologyical Chemistry Research Center, Iran University of Science and Technology, Tehran, Iran</p><p>e i n f o</p><p>ruary 2009vised form 8 April 2009ril 2009e 16 April 2009</p><p>orus pesticides</p><p>alysisidliquid microextraction</p><p>a b s t r a c t</p><p>In this article, a new method for thedeveloped by using dispersive liquidphotometric detection (GC-FPD). Amifor the extraction of OPPs from tea sasolvents was rapidly dispersed in wausing DLLME. Recovery tests were peanalyte was in the range between relative standard deviation, varied bwas found ranging from 0.030 to 1sample preparation method, the propand has high-enrichment factors and/ locate / jhazmat</p><p>traction method fora</p><p>n, Iran</p><p>mination of organophosphorus pesticides (OPPs) in tea wasid microextraction (DLLME) and gas chromatographyameof acetonitrile andn-hexanewas used as an extraction solvents. When the extraction process was nished, the mixture ofarget analyte was extracted to a small volume of n-hexane,ed for concentration 5.0g/kg. The recovery for each target117.4%. The repeatability of the proposed method, expresseden 3 and 7.8% (n=3). The detection limit of the method for teaor all the target pesticides. Compared with the conventionalmethod has the advantage of being quick and easy to operate,onsumption of organic solvent.</p><p> 2009 Elsevier B.V. All rights reserved.</p></li><li><p>908 S. Moinfar, M.-R.M. Hosseini / Journal of Hazardous Materials 169 (2009) 907911</p><p>effective clean-up and extraction steps [17]. Gas chromatography(GC) is a suitable technique for such a purpose [1115] but, dueto low concentration, the compounds of interest have to be sepa-rated from thematrix and concentrated to reach theminimum levelrequired foa new micrpersive liquDLLME are srecovery anthe determiOPPs [19], ctrihalomethphenyltin [2nortriptylin[29], three pphorus and[34] andhalhas been ucides [36] in</p><p>Becauseapplied inwe selectedorganophoslished papeOPPs in teaDLLME suitGC-FPD. Thyield of themized.</p><p>In this stnation of OPand n-hexaThis changeextraction a</p><p>2. Experim</p><p>2.1. Reagen</p><p>All OPPsithion, malapurchasedfrom Mercktimes and was a solventMerck. Alsostandard) wused for thewas dissolva concentradard solutio4 C. The tea</p><p>2.2. Instrum</p><p>A gas chinjector systhe separa(99.9999%,sieve trap aUSA) was u35 cm/s. Thless modewas used iseparationcolumn wit</p><p>dimethyl polysiloxane (Phenomenex, USA). The oven temperaturewas programmed as follows: initial 100 C, from100 C (held 2min)to 150 C at the rate of 25 C/min, from 150 to 175 C at the rateof 5 C/min, from 175 to 195 C at the rate of 2 C/min, from 195</p><p>C aC runC, h-220air</p><p>c cuginraturntroL scrwerK) fotion</p><p>mple</p><p>his stas stem</p><p>g off aceh ratpm)ents,r it oof th(ga</p><p>cap g-distloudyt tubfact,tion2 (DmaOPP</p><p>ltratratep oft ond on(380</p><p>ts ofuse thconichexaing tare</p><p>onsur ceide dat coeadvC. Thtubeyringrecoof ag/Ln levtes wr the particular detector used. In the previous research,oextraction technique was demonstrated named dis-idliquid microextraction (DLLME). The advantages ofimplicity of operation, rapidity, low time and cost, highd enrichment factor [18]. Thismethod has been used fornation of polycyclic aromatic hydrocarbons (PAHs) [18],hlorobenzenes [20], chlorophenols [21], phenols [22],anes [23], polychlorinated biphenyls [24], butyl and5] ionizable organic compounds [26], amitriptyline ande [27], polybrominated diphenyl ethers [28], anilineshthalate esters [30], phthalate esters [31], organophos-plastizicers [32], triazine herbicides [33], antioxidantsogenatedorganic compounds [35] in liquid samples andsed for the determination of organophosphorus pesti-</p><p>watermelon and cucumber samples.organophosphorus pesticides are the most widelymainland Iran to control agricultural crops insects,10 types of OPPs as the representative species of</p><p>phorus pesticides. However, to date, none of the pub-rs have reported the use of DLLME for the analysis ofsample by GC-FPD. The aim of this study is to assess</p><p>ability for the determination of OPPs in tea sample bye effects of different experimental parameters on thesample preparation step were also studied and opti-</p><p>udy, we have developed a new method for the determi-Ps in tea after extraction with a mixture of acetonitrilene concentration with the developed DLLME DLLME method was done to use any solvents in</p><p>nd decrease detection limit.</p><p>ental</p><p>ts and standards</p><p>(phorate, diazinon, disolfotane,methyl parathion, sum-thion, fenthion, profenphose, ethion, phosalone) were</p><p>from polyscience (Niles, USA). n-Hexane was obtained(Germany). This solvent was distillated at least twoas used as an extraction solvent. Acetone, acetonitrile(suprasolv or gas chromatography) were obtained fromsodium chloride and triphenylphosphate (as internalere purchased from Merck. Doubly-distilled water waspreparation of aqueous solution. Each OPP (0.01000g)</p><p>ed in 10.0mL acetone to obtain a standard solution withtion of 1000mg/L. A tea from 20.0mg/L of OPPs stan-n was prepared in acetone every week and stored atsample was obtained from local supermarkets.</p><p>entation</p><p>romatograph (Shimadzu GC 2010) with a split/splitlesstem, and a ame photometric detector was used fortion and determination of OPPs. Ultra pure heliumAir Products, UK), which passes through a molecularnd oxygen trap, (Chromatography Research Supplies,sed as the carrier gas at constant linear velocity of</p><p>e injection port was held at 250 C and used in the split-with splitless time 0.5min. A deactivated glass linern order to decrease the degradation of products. Thewas carried out on a BP-5, 28.5m0.22mm capillaryh a 0.25-m stationary lm thickness, 5% phenyl/95%</p><p>to 275one Gat 300(OPGUof zeroscienticentriftempeture coAll 5mvessel)1200, Uimentastep.</p><p>2.3. Sa</p><p>In tGilan,wat roomand 1.02mL ople wit(1000 rof solvto lte0.5mLsyringescrewdoubly</p><p>A cthe tes</p><p>In(extracin stepa goodextractsity ofconcenThe cawas pufastenetrifugedrople becaat theinto n-</p><p>SavDLLMEwere c</p><p>Aftean upslected(zerodinto Gof testmicros</p><p>For200Lto 200catioreplicat the rate of 10 C/min (held 5min). The total time forwas 32min. The FPD temperature was maintained</p><p>ydrogen gas was generated with hydrogen generator0s, Shimadzu) for FPD at a ow of 80mL/min. The ow(99.999%, Air Products) for FPD was 120mL/min. Theenturion centrifuge (model 2010D, UK) was used forg. In order to investigate the temperature effect, lowe incubator (LTI-601SD,EYELA, Japan)andalso tempera-lling centrifuge (K240R, Centurion Scientic)were used.ew cap glass test tubes with conic bottom (extractionemaintained at 500 C in furnace (Carbolite,model CWFr the cleaning of any organic compounds and good sed-of ne droplets of extraction solvent in the centrifuging</p><p>s preparation and method development</p><p>udy, 2.0 g of green tea which is produced on the elds ofprayedwith 200L of standard solutionOPPs and driedperature. After 24h, the spiked sample was powderedthe powder sample was weighed in a capped vial. Thentonitrile and n-hexane mixture was added to the sam-ios of 250 and 3, respectively, and magnetically stirredfor 45min at 42 C. Therefore, by adding the mixturethe OPPs were extracted from tea. So there is no needr change the solvents ratio. After the tea being settled,e mixture of solvents in the capped vial using a 1.00mLstight, Hamilton, USA) was injected rapidly into a 5mLlass test tube with conic bottom containing 5.00mL ofilled water. Then the mixture was gently shaken.solution (water/acetonitrile/n-hexane) was formed in</p><p>e.acetonitrile and n-hexane that were used in step 1) acted respectively as disperser and extraction solventsLLME). These two steps were coupled together in suchnner that makes this method a suitable procedure tos from the tea without changing solvents and neces-tion. After the extraction of OPPs (step 1), analytes wered in the second step and ready to use for GC analysis.screw cap glass test tube was punched and a septumthe test tube to seal it, then the punched screw cap wasthe test tube. Next it was put upside down into cen-0 rpm) for 3min. After this process the ne dispersed</p><p>n-hexanewere collected at the conic bottomof test tubee dense of n-hexane is less than that ofwater, it collectsbottom of the test tube and OPPs were concentratedne and the tiny particles of tea were precipitated.ime and energy and eliminating ltration step beforethe advantages of using n-hexane. Besides, less OPPsmed compared with conventional methods.ntrifugal process, the test tube was xed by a clip inown position. Then 0.50L of n-hexane, which is col-nic bottom, was removed using 1.00L microsyringeolume, cone tipneedle, SGE, Australia) andwas injectede volume of n-hexane collected at the conic bottomwas about 5.0mL which was determined by a 10Le.very studies, 2.0 g of tea sample was spiked withworking solution containing the pesticides from 100</p><p>, depending on the compound, corresponding to forti-els of approximately 0.0120.0ng/g, respectively. Threeere analyzed in each case.</p></li><li><p>S. Moinfar, M.-R.M. Hosseini / Journal of Hazardous Materials 169 (2009) 907911 909</p><p>3. Results and discussion</p><p>Since, in this study, acetonitrilewasusedas anextraction solventfrom tea in step 1 and as a disperser solvent in the DLLME (step 2),it should have some properties such as: miscibility in water, goodextractor and high boiling point. Among four solvents (acetonitrile,acetone, methanol and ethanol) which have the property of misci-bility in organic and aqueous phase, acetonitrile is chosen becauseit has the highest boiling point as an extraction solvent from teaand as a disperser solvent in DLLME. In developed DLLME the den-sity of the concentration solvent should be less than water, becausein DLLME step (step 2), concentration solvent is collected in theconic bottom of the test tube. Among solvents which have less den-sity than water, n-hexane is mostly used to extract OPPs and othercompounds [37].</p><p>3.1. The optimization of the DLLME method (step 2)</p><p>In order to evaluate the effect of concentration solvent volume(n-hexane), solutions containing different volumes of n-hexanewere examined by the same DLLME procedures. The experimen-tal conditions are xed and include the use of 2.00mL acetonitrile(as extraction solvent from tea) containing different volumes of n-hexane (20.0, 24.0, 28.0, 32.0, 36.0, 44.0 and 48.0L), when addedto1g tea. This shown inof the concevolume of tthe conic bof n-hexanesolvent in s</p><p>From2mvent remainarea decrearesult, theFrom 2mL0.5mL whito conic botsyringe.</p><p>3.2. The effefrom tea</p><p>The varivent in the</p><p>Fig. 1. The efffrom DLLME. Event (acetonitin tea, 2g/kg</p><p>Fig. 2. The effect of a volume of acetonitrile on the peak area of OPPs obtained fromtea. The extraction conditions: as shown in Fig. 1 in 45min.</p><p>causes change in the volume of upper residual phase. To avoidthis change and to achieve an optimum volume of the collectedn-hexane at the conic bottom the volume of acetonitrile waschanged. T</p><p>cond 4.0e of a, 2.0m</p><p>e eff</p><p>his mtactstar0.5md warangeshowing t</p><p>follacco</p><p>lt eff</p><p>he effect of the extraction time on the peak a...</p></li></ul>