Ionic liquid based dispersive liquid–liquid microextraction for the extraction of pesticides from bananas

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<ul><li><p>Journal of Chromatography A, 1216 (2009) 73367345</p><p>Contents lists available at ScienceDirect</p><p>Journal of Chromatography A</p><p>journa l homepage: www.e lsev ier .com</p><p>Ionic li roefor the</p><p>Lidia M. nsioMiguel Departamento a LaguAvenida Astrof</p><p>a r t i c l</p><p>Article history:Available onlin</p><p>Keywords:Room temperature ionic liquidsDispersive liquidliquid microextractionPesticidesBananasHigh-performExperimental</p><p>dliqgh-peof eihexy</p><p>homogenizedandextracted (1 g)with acetonitrile andafter suitable evaporationand reconstitutionof theextract in 10mL of water, a DLLME procedure using 1-hexyl-3-methylimidazolium hexauorophosphate</p><p>1. Introdu</p><p>In recening and minof alternathigh quantmicroextrato conventphase micrsingle-dropsive liquidRezaee etpretreatmeof operatiofactors, lowduction, D</p><p> CorrespoE-mail add</p><p>0021-9673/$doi:10.1016/jance liquid chromatographydesign</p><p>([C6MIM][PF6]) as extraction solvent was used. Experimental conditions affecting the DLLME procedure(sample pH, sodium chloride percentage, ionic liquid amount and volume of disperser solvent) wereoptimized by means of an experimental design. In order to determine the presence of a matrix effect,calibration curves for standards and fortied banana extracts (matrix matched calibration) were stud-ied. Mean recovery values of the extraction of the pesticides from banana samples were in the range of6997% (except for thiophanate-methyl and carbofuran, which were 5363%) with a relative standarddeviation lower than 8.7% in all cases. Limits of detection achieved (0.3204.66g/kg) were below theharmonized maximum residue limits established by the European Union (EU). The proposed method,was also applied to the analysis of this group of pesticides in nine banana samples taken from the localmarkets of the Canary Islands (Spain). To the best of our knowledge, this is the rst application of RTILsas extraction solvents for DLLME of pesticides from samples different than water.</p><p> 2009 Elsevier B.V. All rights reserved.</p><p>ction</p><p>t years there has been a growing interest in simplify-iaturizing sample pretreatment steps, the introduction</p><p>ive non-contaminant solvents and in decreasing theities of organic solvents used. In this sense, differentction techniques have been explored as alternativesional sample preparation procedures, such as solid-oextraction (SPME), stir-bar sorptive extraction (SBSE),microextraction (SDME), etc. Among them, disper-</p><p>liquid microextraction (DLLME) rstly developed byal. in 2006 [1], has been reported as a useful samplent procedure due to its main advantages: simplicityn, low time and cost, high recoveries and enrichmentconsumption of organic solvents, etc. Since its intro-</p><p>LLME has been applied for the extraction of several</p><p>nding author. Tel.: +34 922 31 80 46; fax: +34 922 31 80 03.ress: mrguez@ull.es (M.. Rodrguez-Delgado).</p><p>organic and inorganic compounds mainly from water samples[19].</p><p>Concerning pesticide analysis, DLLME has been mainly usedfor the extraction of these compounds from waters [1012] andin a much lower extent for their analysis in foods. In fact, tothe best of our knowledge there only exist ve works in the lit-erature concerning the DLLME of pesticides from food matrices[1317]. In these studies, 2 insecticides (carbaryl and triazophos)have been determined in peach, grape and apple juices [16],10 insecticides (phorate, diazinon, disolfotane, parathion-methyl,sumithion, malathion, fenthion, profenophos, ethion and phos-alone) in tea [17], 3 fungicides (captan, folpet and captafol) inapples [15], 6 insecticides (malathion, chlorpyrifos, buprofezin,triazophos, carbosulfan and pyridaben) in tea [14] and other 6insecticides (ethoprophos, parathion-methyl, fenitrothion, mala-tion, chlorpyrifos and profenophos) in watermelon and cucumber[13]. In all these works, conventional solvents, in general, chlo-rinated solvents (tetrachloroethane [16], chlorobenzene [13,15],carbon tetrachloride [14] and n-hexane [17]) were used.</p><p>In the last decade, the use of room temperature ionic liquids(RTILs) as extractants has been found to be especially important</p><p> see front matter 2009 Elsevier B.V. All rights reserved..chroma.2009.08.012quid based dispersive liquidliquid micextraction of pesticides from bananas</p><p>Ravelo-Prez, Javier Hernndez-Borges, Mara Asengel Rodrguez-Delgado </p><p>de Qumica Analtica, Nutricin y Bromatologa, Facultad de Qumica, Universidad de Lsico Francisco Snchez s/n, 38206 La Laguna, Tenerife, Spain</p><p>e i n f o</p><p>e 13 August 2009</p><p>a b s t r a c t</p><p>This paper describes a dispersive liquiture ionic liquids (RTILs) coupled to hicapable of quantifying trace amountstebuconazole, iprodione, oxyuorfen,/ locate /chroma</p><p>xtraction</p><p>-Ramos,</p><p>na (ULL),</p><p>uid microextraction (DLLME) procedure using room tempera-rformance liquid chromatographywith diode array detectionght pesticides (i.e. thiophanate-methyl, carbofuran, carbaryl,thiazox and fenazaquin) in bananas. Fruit samples were rst</p></li><li><p>L.M. Ravelo-Prez et al. / J. Chromatogr. A 1216 (2009) 73367345 7337</p><p>in analytical chemistry (in order to replace the volatile onesused during sample preparation procedures) because of theirnegligible vapor pressure, good solubility for organic and inorganiccompounds, non-ammability, high thermal stability, wide tem-perature rauseful in lithis case aand costly.or DLLME bthe use ofsolvents, usinto HPLC s</p><p>To date,poses. In facmajority ofsamples [20for the extral. [20] inwandhexythor theworkmethyl andriver waterinsecticidesand biphennow, otherby IL-DLLMcomplexitytics of the ILcompatibilifore, extendpreconcentgreat interetechnique.</p><p>The aimmethod forbananas usicides (i.e. thiprodione, oto differentwidespreaddesignmethparametersamount andmethod forcial bananaof the EU pour knowlesolvents inwaters (fruthe highest</p><p>2. Experim</p><p>2.1. Chemic</p><p>Pesticidefuran, carbfrom Riedehigher than(SigmaAldvidual stockwere prepaand storedprepared byworking sotures with A</p><p>Methanol and ACN of HPLC grade were from Scharlau(Barcelona, Spain). Acetone of analytical reagent grade wasfrom Merck (Darmstadt, Germany). Anhydrous magnesium sul-phate, sodiumchloride, sodiumhydrogencitrate sesquihydrate and</p><p>cithlorlimid-merovid</p><p>para</p><p>C anilforsam</p><p>e andal co-Pak-colrforCN awasic forcurvmintionn waThelway0nmA10Sta</p><p>cs (Rdata</p><p>nana</p><p>anal mane gmLroprarefutemp. Theakend penhydiumateiatelxturemin./25and(Bced wCl)ribe</p><p>LLME</p><p>soluuget) aninjenge as a liquid phase, etc. [18,19]. They are thereforequidliquid extraction (LLE) applications, although inlarge volume of RTILs is required making it tediousThus, microextraction techniques like SDME, SPMEased on RTILs are preferred. With respect to DLLME,RTILs can replace the use of highly toxic chlorinatedually employed as extractants, with a simple injectionystems after dilution [20].IL-DLLME has hardly been explored for extraction pur-t, only six applications havebeenproposed [2025], thethem dealing, once more, with the extraction of water24]. Only in three of these works, IL-DLLME was used</p><p>action of pesticides. This is the case of the work of Liu ethich four insecticides (pronil, chlorfenapyr, buprofeziniazox)weredetermined in tap, lakeand fountainwaters,of Zhou et al. [21] inwhich two insecticides (parathion-phoxim) were analyzed in rain, ground, reservoir ands and the work of Zhou et al. [22] who analyzed ve(cyhalothrin, deltamethrin, fenvalerate, tauuvalinate</p><p>thrin) in tap, ground, river and reservoir waters. Up tosamples different than waters have not been extractedE for the analysis of pesticides, probably, because of theof the matrices and also, because of the characteris-s required: extremely low solubility in the sample andty with the subsequent separation technique. There-ing the application of IL-DLLME for the extraction andration of pesticides from non-aqueous matrices is ofst in order to fully demonstrate the potential of this</p><p>of this work is the development of a selective IL-DLLMEthe determination of trace levels of eight pesticides inng HPLC with diode array detection (DAD). These pesti-iophanate-methyl, carbofuran, carbaryl, tebuconazole,xyuorfen, hexythiazox and fenazaquin),which belongchemical families, have been selected because of theiruse in the treatment of banana pests. Experimentalodologywasused for theoptimizationof theextraction(sample pH, sodium chloride percentage, ionic liquidvolume of disperser solvent). The application of the</p><p>the analysis of these pesticides in different commer-samples from the Canary Islands (rst banana producerroduction regions) was also carried out. To the best ofdge, this is the rst application of RTILs as extractionthe DLLME of pesticides from matrices different thanits) and also the rst application of IL-DLLME in whichnumber of pesticides has been extracted.</p><p>ental</p><p>als and reagents</p><p>analytical standards of thiophanate-methyl, carbo-aryl, iprodione, hexythiazox and fenazaquin werel-de-Han (SigmaAldrich, Madrid, Spain); purity was98.0%. Tebuconazole and oxyuorfen were from Flukarich,Madrid, Spain); puritywas higher than99.6%. Indi-solutions of each pesticide of approximately 500mg/L</p><p>red by dissolving each compound in acetonitrile (ACN)at 4 C. Mixtures of appropriate concentration wereappropriate combination and dilution with ACN. The</p><p>lutions were prepared daily by dilution of these mix-CN.</p><p>sodiumhydrocmethybutyl-3were p</p><p>2.2. Ap</p><p>HPLtem (Man autostoragpersona NovaC18 prewas pe100% Aditionisocrat4min (over 5theelupositiomore.ume aand 22system</p><p>TheGraphisis and</p><p>2.3. Ba</p><p>Banin location). Othe 50an appwere croomcedureand shtion an2g of aof sodgencitrimmedthe mifor 10PET-45many)R-200dissolv1.0M Has desc</p><p>2.4. D</p><p>Thecentrifsolvendiatelyrate tribasic dihydrate were for SigmaAldrich whileic acid was from Merck. The ionic liquids 1-hexyl-3-azolium hexauorophosphate ([C6MIM][PF6]) and 1-thylimidazolium hexauorophosphate ([C4MIM][PF6])ed by Fluka; purity was higher than 97.0%.</p><p>tus and software</p><p>alyses were performed on a Waters Alliance HPLC sys-d, MA, USA), equipped with two pumps (model 1525),pler (model 717 plus) and a DAD (model 2996). For dataevaluation Empower 2 software from Waters and a</p><p>mputer were used. Separations were carried out usingC18 column (150mm3.9mm, 4m) and a Guard-Pakumn (4m), both from Waters. Gradient HPLC elutionmed with 100% Milli-Q water as mobile phase A andsmobile phase B. The initialmobile phase gradient con-75:25 of solvents A and B, respectively. The elution wasthe rst 3min and was altered gradually to 45:55 over</p><p>e 3). Then, the eluent compositionwas changed to 40:60(curve 7) and later to 100% B for 10min (curve 5). Then,was isocratic for5minandnally, the initial eluent com-s restored in 5min (curve 6) and maintained for 5minow rate was set at 1.0mL/min and the injection vol-s was 20L. The working wavelengths were 205, 215. Milli-Q water was obtained from a Milli-Q gradientfrom Millipore (Bedford, MA, USA).</p><p>tGraphics Plus Software Version 5.1 from Statisticalockville, USA) was used for experimental design analy-processing.</p><p>samples</p><p>samples (ecological and non-ecological) were boughtrkets and supermarkets of Tenerife (regional produc-ram of homogenized bananas (1 kg) was weighed intocentrifuge tube and spiked with a small volume ofiate standard mixture solution. Samples and standardslly mixed (with the help of ultrasounds) and left aterature for at least 30min before the extraction pro-n, 5mL of ACN were added and the tube was closedvigorously by hand for 1min. To induce phase separa-sticide partitioning, a buffer-salt mixture (consisting ofrous magnesium sulfate, 0.5 g of sodium chloride, 0.5 g</p><p>citrate tribasic dehydrate and 0.25g of sodium hydro-sesquihydrate) was added. The tube was closed andy shaken vigorously on a Vortex mixer for 1min. Then,was sonicated for 5min and centrifuged at 4000 rpm</p><p>The supernatant was ltered through a Chromal Xtralter (pore size 0.45m, Macherey-Nagel, Dren, Ger-evaporated at 40 C and 205mbar using a Rotavaporhi Labortechnik, Flawil, Switzerland). The residue wasith 10mL of Milli-Q water at pH 2.7 (adjusted with</p><p>containing 28.9% NaCl (w/v) and subjected to DLLME,d below.</p><p>procedure</p><p>tion previously obtained was placed in a 15mL glasstube. A mixture of 88mg of [C6MIM][PF6] (extractiond 714L of methanol (disperser solvent) was imme-cted into the sample solution in order to induce the</p></li><li><p>7338 L.M. Ravelo-Prez et al. / J. Chromatogr. A 1216 (2009) 73367345</p><p>formation of a cloudy solution, which consisted in ne droplets ofIL dispersed in the aqueous sample. The mixture was subsequentlycentrifuged for 20min at 4000 rpm and the upper aqueous phasewas removed with a syringe (dispersive particles of IL were sed-imented at the bottom of the centrifuge tube). After this process,the IL phase (20L) was dissolved in ACN (the nal volume was125L) and 20L was injected into the HPLC system for analysis.</p><p>3. Results and discussion</p><p>3.1. HPLCDAD method</p><p>The group of pesticides selected in this work consists of eightpesticides (thiophanate-methyl, carbofuran, carbaryl, tebucona-zole, iprodione, oxyuorfen, hexythiazox and fenazaquin) thathave been widely used in the Canary Islands (Spain), especiallyfor banana production. Bananas represent nearly the 30% ofthe regional agricultural production, being the most importantcrop of the islands in economic terms and the second in cul-tivated area (after wine grapes). It should be mentioned thatvery recently (at the end of 2008) the use of both carbofuranand carbaryl was forbidden in Europe for agricultural pur-poses sinceDirective 9http://ec.eu .seleApril). Evencorroboratemonths.</p><p>In orderticides, sevecarried out.A) and 100these experprovided apin terms ofusing the ghand, the sferent waveof maximumcarbaryl anthus, furtheshows the oby HPLCDit can be seeobtained. Twhich highall disappea</p><p>Fig. 1. HPLCabsorbance w100% ACN. Flotion volume: 2(2) carbofuraniprodione (2.3fenazaquin (2.</p><p>to eliminate them by suitable changes of the quality of the solventsormobile phase composition, changes in the gradient program, etc.these chromatographic peaks could not be completely eliminated.Even though, they do not have at all any inuence in the correctdetection a</p><p>Under thstudy at thrthree conseent days (nobtained fotration of 1acceptablewere belowwhile interdand retentiocarried outobtained bydard in tripit can be sewere in thefor tebucon</p><p>and</p><p>liminng thlventity, gtha</p><p>s [26][PF</p><p>]. Moheiro selL of e00ferensing</p><p>imentionntlyut ob</p><p>was cC4M100m6cPlectetheruencime apHthedupesticrentn ofhanoen, t</p><p>phasshoestic(spethe. Asults fd ththey were excluded from Annex I of Commission1/414/CEE (EU Pesticides Database, 2009. Available atropa.eu/sanco pesticides/public/index.cfm?event=activesubstancethough, their analysis is of special interest in order tothepresenceof their residues in bananas in subsequent</p><p>to optimize the HPLCDAD separation of the eight pes-ral experiments with isocratic or gradient elution wereFor this purpose, 100% Milli-Q water (as mobile phase% ACN (as mobile phase B) were used. The results ofiments showed that only the use of gradient elutionpropriate peak resolution. Moreover, the best resultsseparation capacity and retention time were obtain...</p></li></ul>