Application of new high-performance liquid chromatography and solid-phase extraction materials to the analysis of pesticides in human urine

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1 Journl of Chromtogrphy A, 987 (2003) locte/ chrom Appliction of new high-performnce liquid chromtogrphy nd solid-phse extrction mterils to the nlysis of pesticides in humn urine Isbel C.S.F. Jrdim, * Deprtment of Anlyticl Chemistry, Chemistry Institute, Stte University of Cmpins, P.O. Box 6154, , b Josene M. Pozzebon, Soni C.N. Queiroz, Lucio F.C. Melo, Mrcos A. Kpor, Cmpins, SP, Brzil Embrp Environment, P.O. Box 69, , Jguriun, SP, Brzil b Abstrct A method for the simultneous determintion of diuron nd linuron pesticides in humn urine ws developed, using both solid-phse extrction (SPE) nd high-performnce liquid chromtogrphy (HPLC) phses mde in our own lbortory. These mterils were prepred by sorption of polysiloxnes onto silic surfce, followed by immobiliztion. The HPLC columns were prepred from poly(methyloctylsiloxne), PMOS, immobilized onto silic with microwve rdition while the SPE crtridges where mde with poly(methyloctdecylsiloxne), immobilized thermlly. Method vlidtion ws performed for diuron nd linuron for three fortifiction levels. The recoveries obtined were %, the inter- nd intr-ssy precisions were less thn 1.6 nd 1.8%, respectively. The limits of quntittion nd detection for diuron were 2.4 nd 8.0 mg/l nd for linuron were 5.0 nd 12 mg/l, respectively Elsevier Science B.V. All rights reserved. Keywords: Sttionry phses, LC; Sorbents; Pesticides; Siloxnes 1. Introduction effective nd vlidted methods for determintion of pesticides in biologicl fluids re more necessry Exposure to pesticides is concern of the generl ech yer to monitor pesticides in the humn body. popultion, especilly for residents in contminted Urine, very complex nd multicomponent mixsites. Public helth officils re frequently sked to ture, is one of the biologicl fluids of most interest. evlute n individul s risk of developing helth Lrge numbers of compounds ingested or formed in problems from possible exposure to pesticides in the the body by metbolism re excreted in urine. environment. Although most people re not occup- Severl clsses of pesticides re metbolized or tionlly exposed to pesticides, nerly everyone hs degrded to ures or nilines [3 5]. The nlysis of some level of exposure resulting from food, ir, ures in urine cn thus provide n index of exposure wter, or derml contct [1,2]. Thus, fst, esy, to mny of the pesticides in the environment. Selective isoltion of the nlytes from the smples using preconcentrtion procedure is often *Corresponding uthor. Tel.: ; fx: necessry prior to seprtion nd mesurement [6]. E-mil ddress: icsfj@iqm.unicmp.br (I.C.S.F. Jrdim). Mny methods described in the literture for the /02/$ see front mtter 2002 Elsevier Science B.V. All rights reserved. PII: S (02)

2 382 J.M. Pozzebon et l. / J. Chromtogr. A 987 (2003) determintion of ures nd their metbolites mterils were prepred in our lbortory by im- (nilines) in urine require derivtiztion, silic gel mobiliztion of polysiloxnes onto silic surfce. clen-up nd gs chromtogrphy [5,7]. Recently, the use of high-performnce liquid chromtogrphy (HPLC) in this type of nlysis hs been developed, mking possible the determintion of new clsses of 2. Experimentl pesticides. However, the use of solid-phse extrction (SPE) hs not been reported in the literture for 2.1. Chemicls nd mterils determintion of neutrl pesticides in urine by HPLC. Diuron nd linuron stndrds were obtined from New mterils for use s HPLC sttionry phses DuPont nd Hoescht, respectively. Stock solutions of nd s SPE sorbents hve been developed in recent ech herbicide were prepred in methnol t con- yers. These new mterils consist of polysiloxnes centrtions of mg/ml (diuron) nd mg/ sorbed nd immobilized onto n pproprite silic ml (linuron). The solutions used to construct the support. This promising lterntive method, insted clibrtion curves nd to spike the smples were of chemicl rection, uses wide vriety of prepred in mobile phse t concentrtion of 2000 immobiliztion techniques nd hs been successfully mg/l for ech herbicide nd stored in the refrigertor pplied to prepre severl HPLC sttionry phses, t 4 8C. such s poly(methyloctylsiloxne) (PMOS) on zirconcentrtions: 20, 40, 80, 160, 320, 600, 800 nd The clibrtion curves involved eight different conized silic [8,9], titnium-grfted silic [10] nd pure silic [11 15]. A SPE sorbent bsed on poly mg/l for diuron nd 30, 60, 120, 240, 500, 800, (methyloctdecylsiloxne) (PMODS) immobilized 1200 nd 1500 mg/l for linuron. The injections were by g-rdition onto silic hs lso been described mde in three replictes. [16]. The min dvntges of these procedures re Acetonitrile nd dichloromethne were Mllinckgood performnce, lower cost, simplicity nd reducsolvents were nlyticl grde. Purified wter ws rodt chromtogrphic grde. Other regents nd tion of toxic residues. Another method for polymer immobiliztion is obtined from Millipore Milli-Q Plus system. The microwve rdition. This immobiliztion procedure following solvents were used in the preprtion of hs been used to prepre the sttionry phse for the SPE sorbents: n-hexne (Mllinckrodt, HPLC- HPLC columns, using PMOS nd silic. Microwve grde), methnol (Mllinckrodt, HPLC-grde) nd rdition is type of nonionizing energy tht cuses n-pentne (Merck, nlyticl-regent grde). moleculr movement from the phenomen of ionic The silic for SPE ws from Fluk, irregulr migrtion nd dipolr rottion [17 19]. The min prticles, ( mm, mesh), pore dvntge of the use of microwve irrdition is the size 10 nm nd for the HPLC sttionry phses it high-speed heting, since it cn ccomplish therml ws from Phse Seprtions (Spherisorb 5 mm 2 immobiliztion more rpidly thn oven heting. In sphericl prticles, 8.0 nm pore size, 186 m / g ddition, the cost nd the precutions re minimized specific surfce re). PMODS nd PMOS were from if compred with g rdition nd severl other Petrrch Silnes nd Silicones. immobiliztion methods. Vlidtion is one of the most importnt steps in 2.2. Equipment method development for nlyticl determintions. The min prmeters involved re precision (intr- The HPLC system consisted of Rheodyne 7725i nd inter-ssy), recovery, limit of detection (LOD), injector with 10-ml loop, Wters 510 pump nd limit of quntittion (LOQ) nd linerity [20]. Wters UV Vis bsorbnce detector (Model 486). This pper describes the vlidtion of method The dt cquisition nd tretment were performed using SPE nd HPLC for determintion nd quntifi- by CHROMPERFECT softwre, version The mobile ction of the pesticides diuron nd linuron (substi- phse (cetonitrile wter, 40:60, v/ v) flow-rte ws tuted ures) in humn urine. Both the HPLC nd SPE set t 0.8 ml/min nd UV detection ws t 254 nm.

3 J.M. Pozzebon et l. / J. Chromtogr. A 987 (2003) All mesurements were crried out t room temper- sorbent pcked in 5-ml polypropylene syringe. The ture. mteril ws retined by two polyethylene frits (20 The urine smples were centrifuged in n Excels mm pore size). centrifuge, model MP, from Fnem (So Pulo, Brzil). The sttionry phses were irrdited in CCE M-34 microwve oven or heted in ME27F 2.5. Preprtion of the HPLC sttionry phse model oven from Electrolux. A model Hskel pump ws used to pck the A sufficient quntity of silic ws dded to internlly polished [21] HPLC columns. solution of PMOS dissolved in dichloromethne to give mteril with 40% (w/ w) of PMOS. This mixture ws stirred for 3 h before slow evportion 2.3. Urine collection nd storge of the solvent t room temperture. The sttionry phses were irrdited in microwve oven t 495 Urine smples (blnks) from humn volunteers W for 900 s nd then extrcted with chloroform nd were collected nd kept frozen t 220 8C until use. methnol t pressure of 34.5 MP to eliminte After the urine smples hd been thwed, they were excess polymer. Columns were downwrd pcked t shken for homogeniztion. The required volume 34.5 MP in Hskel pump using 10% (w/ v) ws then smpled s quickly s possible to void slurry of the pcking mteril in chloroform with sedimenttion of ny solids. methnol s propulsion solvent Preprtion of SPE crtridges 2.6. Smple preprtion The silic support ws dried t 120 8C for 24 h. A sufficient quntity of support ws dded to solution of PMODS dissolved in n-pentne to give mteril with 40% (w/ w) of PMODS. The mixture ws stirred gently for 3 h t room temperture, fter which the solvent ws evported slowly t room temperture. For therml immobiliztion, n mount of the C18 loded support ws plced in 120 8C oven for 4 h, t tmospheric pressure. After immobiliztion the mteril ws plced in stinless steel tube. This tube ws connected to Wters 510 pump for extrction of ll remining soluble PMODS by pssing pproximtely 25 ml of n-hexne per grm of sorbent, t flow-rte of 2 ml/min. Then, 15 ml of methnol for ech grm of mteril ws pssed through the tube, t flow-rte of 3 ml/ min. To mke sure tht ll soluble residues were removed, n extr extrction step ws mde using high-pressure pcking pump (Hskel), t 1000 p.s.i. (6.9 MP), in proportion of 20 ml of methnol per grm of sorbent. After extrction, the solid-phse ws removed from the tube nd ws kept t room temperture for 48 h for the solvent evportion. The crtridges were prepred using 0.5 g of A 2-ml volume of urine ws fortified by ddition of predetermined volume of the 1000 mg/l of solution contining the herbicides, resulting in three levels of fortifiction, 40, 80 nd 160 mg/ l for diuron, nd 60, 120 nd 240 mg/ l for linuron. The smple ws bsified by ddition of 200 ml of NH4OH (ph 9) nd diluted with 4 ml of cetonitrile. Deproteiniztion ws crried out by centrifugtion (5 min, 3000 g). A 3-ml liquot of the supern- tnt contining urine cetonitrile (1:2, v/ v) ws seprted nd diluted with 20 ml of Milli-Q wter for the extrction procedure. The smple ws percolted through the SPE crtridges under vcuum t flow-rte of 3 ml/min. Before smple ppliction, the SPE crtridges were conditioned with 10 ml of methnol nd equilibrted with 5 ml of Milli-Q wter. After the smple hd pssed through the crtridge by vcuum, the cr- tridge ws wshed with 5 ml of Milli-Q wter. This elute ws discrded nd the sorbent bed ws dried under vcuum for 3 min. The nlytes were then eluted with 3 ml of dichloromethne. The solvent ws evported to dryness under strem of nitrogen nd the residue ws dissolved in 200 ml of cetonitrile. The injection volume ws 10 ml.

4 384 J.M. Pozzebon et l. / J. Chromtogr. A 987 (2003) Method vlidtion the concentrtion of nlyte in smple. For this nlyticl chromtogrphic technique, liner rel- The LOD is the lowest pesticide concentrtion tht tionship is observed between the detector response cn be detected but not necessrily quntified in ( y) nd concentrtion (x) of the nlyte in the smple [22]. The LOD is expressed s concen- smples in the form of liner clibrtion curve trtion in terms of signl-to-noise rtio (S/N). In this obtined by lest-squres liner regression procestudy LOD ws clculted using three times the dures [25] y 5 1 bx where is the intercept of the noise level. clibrtion curve nd b is the slope. The LOQ is the lowest pesticide concentrtion The precision determines the nlyticl devition, which cn be determined or quntified in smple nd is the most importnt criteri for evluting with cceptble precision under the stted opertion- nlyticl method performnce. Precision reflects the l conditions of the method [23]. A S/N rtio of ten vrition in results when repetitive nlysis re mde times the noise level ws used to determine the on the sme smple. The intr-ssy precision ws LOQ. determined on the sme dy nd consisted of three After defining the nlyticl conditions, tests were series nd three replictes t ech of three conmde on the recovery of herbicides fter SPE nd centrtion levels. Inter-ssy precision ws clcu- HPLC. The recovery ws mesured s the response lted in three series nd three replictes t one fter processing mtrix mtched stndrd, ex- concentrtion on three different dys. pressed s percentge of the response of pure The numericl vlue used ws the reltive stnstndrd which hs not been subjected to smple drd devition (RSD) of triplicte mesurements of pretretment. It indictes whether the method pro- the nlytes, using the eqution: vides response for the entire mount of nlyte tht is present in the smple. It is best estblished by RSD s/x m compring the replicte responses of extrcted smwhere s 5 [o (x 2 1/2 i2 x m)/n21], xm5 o x i/n, n is ples t mtrix concentrtions with those of nonexthe totl number of mesurements, nd xi is number trcted stndrds which represent 100% recovery. of the individul mesurements. The recovery ws clculted [24] using the eqution: mss of nlyte fter extrction Recovery 5]]]]]]]]] 3100 mss of nlyte dded 3. Results nd discussion The linerity of method is mesure of rnge within which the results re directly, or by well defined mthemticl trnsformtion, proportionl to 3.1. SPE crtridges Tble 1 shows the results of chrcteriztion tests Tble 1 Chrcteristics of some commercilly vilble C 18 sorbents nd the sorbents obtined by therml immobiliztion of PMODS onto silic Commercil Compny Type of % C End- Pore size Prticle size nme bonding cpped (nm) (mm) Supelclen LC-18 Supelco Si(CH 3) 2C18H37 10 Yes (monofunctionl silne) Bond Elut Vrin SiC18H37 17 Yes (trifunctionl silne) Sep-Pk C18 Wters Si(CH 3) 2C18H37 12 Yes (monofunctionl silne) Sep-Pk C18 Wters SiC18H37 17 Yes (trifunctionl silne) Sorbent from this work C 18 (thermlly immobilized nd extrcted) 15 No

5 J.M. Pozzebon et l. / J. Chromtogr. A 987 (2003) Tble 2 Effect of microwve immobiliztion (495 W, 900 s) on PMOS sorbed on 5-mm Spherisorb silic b Sttionry phse N/m As k R s %C (pltes/ meter) Without microwve tretment With microwve tretment Clculted for the nphthlene pek. b Clculted for the toluene nphthlene pir. of the solid-phse obtined fter therml immobiliztion of polymer nd fter extrction of the excess polymer. These results re compred with some commercil sorbents. For commercil sorbents, the %C rnged from 10 to 17% nd for the sorbent obtined in this work the vlue ws 15%. Thus, the proposed method to obtin PMODS-loded silic, immobilizted by therml tretment, produces mteril with similr fetures to commercil sorbents, especilly with respect to the %C, with the dvntge of being much esier, cheper, less time consuming synthesis process, which uses less toxic solvent thn the trditionl chemicl rection methods HPLC columns Tble 2 presents vlues of chromtogrphic performnce prmeters for HPLC columns prepred by microwve irrdition. The silic ws not previously dried, becuse the wter sorbed on it contributes to fst microwve heting. The results indicte tht microwve irrdition produces n improvement in the efficiency of the sttionry phse nd n immobiliztion of the polymer on the support. The increment in the vlues of %C obtined with immobiliztion, s well s the decrese of the symmetry fctor, re indictive of good coverge of the chromtogrphic support by PMOS through microwve rdition. The prmeters were obtined for test mixture contining cetone, benzonitrile, benzene, toluene nd nphthlene. Chromtogrphic seprtions using columns immobilized by microwve irrdition were utilized to investigte fortified humn urine smples to test the pplicbility of the described nlyticl procedure. A good seprtion of the nlytes ws obtined from spiked urine smples, when compred with blnk smple. Representtive chromtogrms re shown in Fig. 1. Chromtogrms: () blnk urine, (b) urine spiked with Fig. 1. pesticides. Sttionry phse: lbortory-mde poly(methyloctylsiloxne), microwve-immobilized on 5-mm silic; mobile phse MeCN wter (40:60, v/ v); flow-rte 0.8 ml/ min; detection 3.3. Method vlidtion UV t 254 nm; injection volume 10 ml. Elution order: (1) diuron, (2) linuron. The liner regression prmeters with correltion

6 386 J.M. Pozzebon et l. / J. Chromtogr. A 987 (2003) Tble 3 Clibrtion curve nd linerity for the herbicides Herbicide Clibrtion curve Liner intervl b r (mg/l) Diuron Linuron y 5 1 bx, 5liner coefficient, b5ngulr coefficient, r5 correltion coefficient. Tble 5 Limits of detection (LOD) nd quntittion (LOQ) for the herbicides in mtrix mtched stndrds (n53) Herbicide LOD LOQ LOD LOQ (mg/l) (mg/l) (mg/l) (mg/l) Diuron Linuron LOD nd LOQ fter 5-fold preconcentrtion; n53 for ll mesurements. Tble 4 Precision (intr nd inter-ssy) nd recovery for the SPE HPLC determintion of herbicides Herbicide Addition Recovery Intr-ssy Inter-ssy (mg/ l) (%) precision (n53) precision (3 dys) RSD (%) RSD (%) Diuron Linuron n, number of replictes. coefficients (r) nd prmeters of the clibrtion prepred SPE nd HPLC phses ws developed for curves constructed for detection of the herbicide t determintion of diuron nd linuron compounds in 254 nm re presented in Tble 3. urine, with recoveries, precisions nd limits of Tble 4 shows the recovery nd the intr- nd detection nd quntifiction (Tbles 4 nd 5) in inter-ssy precisions of the method. Recoveries greement with the vlues suggested in the literture. were obtined by triplicte nlysis of urine spiked Fst, esy nd effective procedures to obtin with ech compound t three levels of fortifiction silic-bsed C18-type sorbents for use in SPE nd for ech herbicide. C8-type reversed sttionry phses for HPLC ppli- The verge results obtined for herbicide re- ctions re described. Good recoveries were obtined coveries (Tble 4) re very good, 60 10% below with SPE sorbents prepred by therml immobiliz- 100 mg/l nd % bove 100 mg/l, recoveries tion of PMODS on silic (Tble 4), which cn be which re considered cceptble [22]. The results of ttributed to PMODS chin crosslinking, giving n the intr- nd inter-ssy runs show very good extrction phse with excellent retention for these precision, with RSD vlues between 0.4 nd 1.8%, pesticides. The PMOS immobilized on silic by since for biologicl smples RSD up to 15% is microwve irrdition results in high efficiency cceptble [22,26]. HPLC columns (Tble 2) with good seprtion of The results of LOD nd LOQ, before nd fter the herbicides (Fig. 1). The min dvntges of the preconcentrtion, re presented in Tble 5. All these results re for nlysis of urine. procedures to obtin new SPE nd HPLC mterils re good performnce, lower cost, simplicity nd reduction of toxic residues. 4. Conclusions The results presented in this pper show tht vlid, precise, nd specific method using lbortory Acknowledgements The uthors cknowledge finncil support nd

7 J.M. Pozzebon et l. / J. Chromtogr. A 987 (2003) fellowships from the Fundço de Ampro ` Pes- [10] R.B. Silv, C.H. Collins, J. Chromtogr. A 845 (1999) 417. quis do Estdo de So Pulo (FAPESP), Conselho [11] I.C.S.F. Jrdim, K.E. Collins, T.A. Anzw, J. Chromtogr. A 849 (1999) 299. Ncionl de Desenvolvimento Cientıfico e Tecnol- [12] S. Bchmnn, L.F.C. Melo, R.B. Silv, T.A. Anzw, ógico (CNPq) nd trvel support from the Fundo de I.C.S.F. Jrdim, K.E. Collins, C.H. Collins, K. Albert, Chem. Apoio o Ensino e Pesquis (FAEP) of UNICAMP. Mter. 13 (2001) The uthors lso thnk C.H. Collins for helpful [13] E. Tonhi, S. Bchmnn, K. Albert, I.C.S.F. Jrdim, K.E. discussions nd suggestions. Collins, C.H. Collins, J. Chromtogr. A 948 (2002) 97. [14] E. Tonhi, K.E. Collins, C.H. Collins, J. Chromtogr. A 948 (2002) 109. References [15] E. Tonhi, K.E. Collins, I.C.S.F. Jrdim, C.H. Collins, Quim. Nov 25 (2002) 616. [16] S.C.N. Queiroz, L.F.C. Melo, I.C.S.F. Jrdim, J. Chromtogr. [1] R.H. Hill, D.B. Shely, S.L. Hed, C.C. Willims, S.L. A 948 (2002) 171. Biley, M. Gregg, S.E. Bker, L.L. Needhm, J. Anl. [17] H.M. Kingston, L.B. Jessie, in: Introduction to Microwve Toxicol. 19 (1995) 323. Smple Preprtion (ACS Professionl Reference Book), Vol. [2] M.D. Beeson, W.J. Driskell, D.B. Brr, Anl. Chem , Americn Chemicl Society, Wshington, DC, (1999) [18] S.L. Cresswell, S.J. Hswell, J. Chem. Educ. 78 (2001) 900. [3] M. vn Boven, L. Lruelle, P. Denens, J. Anl. Toxicol. 14 [19] A. Zlotorzynski, Crit. Rev. Anl. Chem. 25 (1995) 43. (1990) 231. [20] R. Cuson, J. Chromtogr. B 689 (1997) 175. [4] E.R. Verheij, J. vn der Greef, G.F. L Vos, W. vn der Pol, [21] K.E. Collins, B.C. Frnchon, I.C.S.F. Jrdim, E. W.M.A. Niessen, J. Anl. Toxicol. 13 (1989) 8. Rdovnovic, M.C. Gonçlves, LC?GC 18 (2000) 106. [5] K. Wittke, H. Hjimirgh, L. Dunemnn, J. Begerow, J. [22] D.R. Jenke, Instr. Sci. Technol. 26 (1998) 1. Chromtog. B 755 (2001) 215. [23] I. Krull, M. Swrtz, LC?GC 15 (1997) 534. [6] S.C.N. Queiroz, C.H. Collins, I.C.S.F. Jrdim, Quim. Nov [24] A.A.M. Chsin, E.S. Nscimento, L.M.R. Neto, M.E.P.B. 24 (2001) 68. Siqueir, M.H. Andrus, M.C. Slvdor, N.A.G. Fernıcol, [7] E.M. Lores, F.C. Meekins, R.F. Mosemn, J. Chromtogr. R. Gorni, S. Slcedo, Rev. Brs. Toxicol. 11 (1998) (1980) 412. [25] G.W. Peng, W.L. Chiou, J. Chromtogr. 531 (1990) 3. [8] L.F.C. Melo, I.C.S.F. Jrdim, J. Chromtogr. A 845 (1999) [26] A.A.M. Chsin, M. Chsin, M.C. Slvdor, Rev. Frm Bioquim. 30 (1994) 49. [9] L.F.C. Melo, C.H. Collins, K.E. Collins, I.C.S.F. Jrdim, J. Chromtogr. A 869 (2000) 129.