Optimization of enrichment processes of pentachlorophenol (PCP) from water samples

Journal of Entirormental Sciences Vol. 16,No.l.pp. I7- 20 ,2004IS 101-0742CNI- 2629/%Artice D: 1001-0742( 20010017-0CLC number: X703 Document code: AOptimization of enrichment processes of pentachlorophenol (PCP) from watersamplesLI Ping，LIU Jun-xin(Reserch Center for From- Eninmnental Sciences. Chincse Acadermy of Sciences, Bejing 100850. E mail: lipinglSen@o yahoo . ceom .en)Abstract: The method of enriching PCP< pentachlorophenol) from aquatic environment by solid phase extraction( SPE) was studied.Several factors afeting the recoveries of PCP. including sample pH, eluting solvent, eluting volume and flow rate of water sample, wereoptimized by orthogonal array design( OAD) . The optimized results were sample pH 4; eluting solvent, 100% methanol; eluting solventvolume. 2 ml and flow rate of water sample. 4 ml/min. A comparison is made between SPE and liquid- iquid extraction(LLE) method. Therecoveries of PCP were in the range of87.6%- 133.6% and 79% - 120.3% for SPE and LLE, respectively. Important advantages of theSPE compared with the LLE include the short extraction time and reduced consumption of organic solvents. SPE can replace LLE torisolting and concentrating PCP from water samples.Keywords: pentachlorophenol( PCP); solid phase extraction; liquida. lquid extractionand holistie sysem. For each individual compound, the ficieney of theIntroductionrecovery diflere from each other， which depends on it' s chemiealPCP is acutely loxie to variely of microorganism and marumals as itstrueture and the condition of SPE. A detailed optimization of SPEis an inhibiter of oxidative phosphorylation und is thought to be mutageniecundition would, therefore, help to search for the optimurm condition toor at least cormutugenic. Human exposure to PCP is coasidered to poseget the highest recovery percentage for the special constituents of thesignifcanl health hazards ( Volker,2001 ). In China， sodiumsample .pentachlorophenate( Na- PCP) has been sprayed widely since the 1960s toFor PCP, the development of SPE method involves the investigationcontrol the spread of snailborme scisosomiasis. Although Na-PCP hasof many variables infueneing the efrciencey of extraction. Therefore, howbeen replaced by some new mollusacides since 1990s, the persistence ofto decided these variables and their levels is critical. In this research,PCP resuled in the accumulation in soil and sediments. The remains ofthe selection of the variable scopes was based on the previous informationPCP also proride a source leading to continuous contamination in aquaticrorm SPE ( Giuseppina, 2001; Curini, 2001; Silvia, 1997). In thisenvironment(Zheng. 2000). PCP is also one of by-products generatedprocedure, the scopes should be broad ernough l0 include the possibleoptimum, but not to cause inconvenience in the experment. The levelsresin production, oil rfining. pesticide, paint, solven, wood preseringwere set close 1o the possible optimum 10 get the mosl accuratechemicals，and paper and pulp industries. Most of then flow into aquaticinformation.environment with industil efluents( Wan, 2000).The theory and methodology of orhogonal aray design(OAD). as aTo ases the posible impact of PCP on ecosyslems and support thechemometrie method for the optimization of the analytical proeedure, hasimprovement of remediation lechniques, sficienty selective and highlyben described in detail. In this paper, sevenl factors, which havesensitive analytical procedures are highly desirable for the routine monitorefects on the recovery of the PCP, were studied and optimized by OAD.ofPCP in water. Due to the complexity of wastewater, especially inThe final resuls were employed for the SPE of PCP from aquatiesewage system, for routine monitoring of PCP in waslewaler, the gasenvironment.chromatngraphy and high performance liquid chromatography areA comparative study between LLE and SPE is also crried out in theimportant and efcive methods ( Vriendt, 2001; Michela， 2000).research.During the analysis procedures, PCP must be isolated and1 Materials and methodspreconcentrated from the water sample before chromatographicmeasurements. In general. LLE and SPE are adopted. The forner is.1 Chemicalsbased on solvent partitioning in separating funnels. LE is frequenlyused for the isolation of pesticides from water sample ( Christian, 2000;Dislled deionized water was used throughout the experiment . PotassiumPrilla，1997). Dichloromethane is the commonest solvent because it ishydrogenophosphate and phosphorie acid with analytical grade were usedcapable of extracting cormpounds with a wide Trang of polarities and easyfor the preparation of buffer solutions and 8s part of the mobile phase.10 evaporate. However, IE produces emulsion compounds, requiresStock solution was prepared hy dissolving PCP 10 mg in 10 ml methanol,large mounts of solvent, and is laborious and difcult to automate .Working standards solutions were prepared by approprate dilution ofSPE, has been widely used to isolate the unalytes from the waterstock solution with deionized water. When not in use, all the solutionswere stored at 4C in a refrigerator .line. there are many factors, which an analyst has t0 take into中国煤化工。consideration in extraction process. Aquatie environment is a complex0.45 pum porous nylon0HCNMH GFoundution iten: The" Hundred Talent" Progran, and thr Knowledge lnovation of the Chinese hcacerny orsar18LI Ping etal.Vol.I6menmbrane filer of 50 mm diameter to remove all the pricles that wouldB.=(79.5+73.7obstnuct the cartrige . The samples were driven through the catridges hy+91.3)13 = 81.5%，similar. B, = (76.3 + 89.5 + 82.5)/3 =means of negative pesure from water pump. For the reovery82.7% . The diferent means at the two levels of a factor reveal how therescareches, walter samplea were forifed with knowamnountsof thereovery change with the change of the factor level. The average recoverystandard slution and agitaled vigroualy for apoximate 1 min, thenof each factor at dferet levels was calculaed and is sumnarized inpoured intoglass reservnir, respectively. which connec1ed to theTable 2 and Fig. 1.adsortbent eartridge. The sample pH was adjusted to corresponding valueTable 1with phosphoric acid or potassium hydroxide. The extracion cartridgeswere rinsed by driving 5 ml of methano through the cartridge. and then.using an 0AD,(3*) matrix and the resuts of the efets of selected varlablesfllowedby 10 ml of water adjusted to the same pH as the sample.o the recoveryFactorResultTellon tuhes were coneeted between sample reservoir and carridges.(A)Supple. (B)Eluing (C)Fluing (D)Flow Recovery.Sarmple loading was performed at a designation flow rate under vacum.numbersolvent volume. ml rate of water%The sorbent was never alwed to dry during the rinsing and samplemethanol,sample,loading procedures. After extraction, most of the waler was renoved fromm/minthe cartridges by forcing the room air through them for 10 min. Elution(1) 7(1) 100(1)4(1) 1276.3was performed by gravity, but a litle pressure was put on at the end of(2) 90(2) 2(2) 879.5《1) 7(3) 803) 1elution. Dfferet elution solvents and elution volumes were tested. Th(2)52) 2(3)489.5eluate was analyzed by HPLC.(2) 573.71.3 LLE procedure1)484.0w ater samples were flered hrough millipore membrane filer(0.45(3)3(3) 182.5pm) before this procedure, and then frified with known amounts of the(3)3.91.3standard solution. After agiation, 200 ml of water sample was acidifed(3) 3(2)280.8to pH = 4 ly adding of phosphorie aeid and extracted twice withdichloromethane(50 ml + 25 ml) in a 500 m! separatory funnel andTable2 The average recovery of every level and the rang of each variablesvigorous shaking. The combined extractes were concentrated to(%)(A) Sample(B)Eluting(C)Ehuting (D)Sample walerapproximately 2 ml by K-D concentrator，and then evaporated to drynessHsolvent,呢volune.ml low rate, m/minunder the condition of gentle nitrogen stream . The residue was dissolvedLevel 176.182.783.876.9in 2 ml mehanl and anualyzed by HPIC.level2 82.481.583.282.01.4 Mensuration procedureLevel 384.879.176.2The concentration of PCP was analyzed by HPLC system. TheRange.7_3.7.67.analytical column: iregular.HC18 mieron 4.6 id x 25 cm; columntermperature: 40C. the UV detector operated al 248 nm，mobile phaseThe importance of each variable on the recovery was presented bycmpment: methanl : bffer= 85:15(v/v). Bufter of0.01 mol/L range(R). The R equal to the dferere betwen the maxinum andpasum hydngnphasphale was adjused to pH= 4 wih phosporie minimum level mean of rovery in the sanme factor. The resulh is shownacid, flow rate, I ml/min.in Table 2. Visual relationship between the level mean of averageThe concentrations of the PCP in the waler samples were caleulatedrecoveries and the level of different factors are shown in Fig. 1.by measuring the PCP preak and compared with those obtained frormstandard solutions.. AlI solvents and samples were filtered throughmillipore memhrane filters before injcction into the columt.8oF 士D2 Results and discussion2.1 Optimization of SPE procedureIn this experimenl, four major facors that may elet the SPE之eficiencey were studied. These factors are as fllows: the pH of sample,Lovel7.5 and 3( factor A), eluting solvents, methanol, 100%， 90% and80% (actor B). eluting solvent volume, 4 ml, 2 ml and 1 m( faclor C)Fig. 1 Relationship belwen the level means of avenagrand sample flow- rate, 12 m/min, 8 ml/min and 4 ml/min(factor D). Inrecoreries and the faetor leelthis work， because a teelevel and four-facor variable will beTable 2 and Fig.1 show that water sample pH have significantoplimized, an 0AD。(3* ) malrix is employed to assign the factors. Thecfectes on the average recovery of PCP( range = 8.7. the largest in fourassignment of the faclos and the levels in this design and lhe resuls offactors). PCP is a hydrophobic ioniable oganic compound with a pK.the experiment are summarized in Table 1 .of4.75. When the pH value of waler sample was higher than5 most ofThe average level means of the recoweries of each factor werePCP中国煤化工st PCP exist in neural form.calculated acording to he asignnent of the experinents. For examople,二%，when the pH was loweredto oblain the level mean of factor B at level 2 in this experiment, therom |IYHCN M H Gei icee hom 82.4%0recovery data of three trials in level2 of B (rials2, 5, and 8, Table 1)No.lOptimization of enichnent proceses of pentaclorophenol (PCP) from water samples84.8%，whrn the H was lowered from 5 to 3(fom level 2 1o level 3) .velority 0! SPE is faster than LE，especially when water samplesThe dferet roveres for PCP at various pH water samples pethapscomprise high concentration of dissolved onganic carhon, which thehave dely rlations with he existing form of PCP. Subsequentexperiments were crried out, the sample pH was designed by4, 3. 2,is more practical to extract many saumples using SPE al the same time.and I, and other conditions are similar to trial 8. The curves were madeThird, less time and less organie solvents are necded for clening of glassfor sample pH and the recovery of PCP. The result is that the range ofequipment，because disposable SPE eartridges are used for extraction.them was not more than I. Because pH =4 are more closed to normal3 ConclusionspH value of aquatic environment.So pH=4 was chosen lor furtherexperiments .A SPE method to analyze the concentration of PCP in various waterIn this research, three elution solvents chosen were lested, 100%samples have been developed and valdated in this experimentalmethanol, 90% methanol, and 80% methanol. The average recoveryresearch. Compared with IIF, SPE has udvantages, e.g. rapid. lessderrased from 82.7% tn 79.1%，for diferent elution sovents. Thelabor inteusity and reducing the need of solvent, which is hazardous andexpensive.So SPE can replacc LLE for isolating and concentrating PCPthe elution solvent was not a major faclor that aetis the recovery offrom aquatic environment .PCP. PCP could almost be eluted by either of these eluin solvents. butReferences :using 100% methanol can obtain a litle higher recovery for PCP.The variation in PCP recovery as a function of elution solventChistian W T, Olav L, Agnetbhe L. 20000 Derelopment ol a solid-phase1 this work. The range of factor(C) was7.6. Soelution solvent volume had also significant efect on the recovery of PCP.a liquid-liquid extruetion method[J]. J Agnie Foord Chen，48: 5829- -5833.However. Fig. 2 shows that the recovery of the facto(C) between levelCurini R, Cenili A. Marechese S e al..2001. Monioring of pesticides in surftce| and level 2 apprnached a plateau region of the curve. ht showed that 2waten of-line SPE fllowld by HPLC with Uv deteetion and confirmnatoryanalysis by nass spectronetryl J]. Chromatognophia. 53: 244- 250.ml and 4 ml elution solvent has almost the sirnilar eficiencey of elution.But for the sarme water samples, the limit of detection for 2 ml elutionDivincenzo JP, Sparks D L. 2001. Sorpion of the neutal and cherged forms ofpentachlophenol on soil: eridenre for dfferet mechanisms [J]. Areisolvent was 1/2 for 4 ml, and the methanol used for elution is alsoEnvion Contam Toxicol, 40: 44- 450.reduced . Therefore ，2 ml methanol was chosen for funher experiments.Divincen2o0 J P. Spurks D L, 2001. Sorption of the neutral and changed forms ofThe ee of 0ow rate on recovery was investigated at three diferentpentachorophenod on soil: eridence for dilereet mechanisms:J]. Archflow rates4, 8 and 12 ml/min. The average recovery for PCP drop fromEniron Contam Torxieol, 43: 445- -450.84.4% to 76.7% when the flow rates increuse lo 12 ml/min from 4 mUGiusepina M, JHobert T, Marta A a al. .2001 . Determinaion ol 5-aurouacilmin, and the range = 7.5. The experiment results showed that the f1owin enionmental samnples by solid-phase extaction and hiheforormanre liquidrale is also the major variableelecting the recovery for PCP. The lowerchomatgaply with ultaviolet detertiolJJ. Journal of Chronalograpbhy B.low rale is, the higher recovery will get. However, lower flow rales will750: 25- -32.Lawrence M，199. Can adsopion isotherms prediet sediment bioawailability?sample volumes are ued. So in this experiment 4 m/min was echosen asChensphere. 41: 1091- 1100.ptimum sample flow rate.Michael Gs, Donald LS, Stevren K D.1994. Sorpion of pentachopherol toIIDTMA-lay as a function of ionie mtter[JI. Environ Sei Technol, 28:2.2 Validation and comparison of SPE and LLEThe SPE method was ppied in routine analysis and empared withMichela P. Gianluca B. Fabio C, 2000. Dermination of phenoxalkanoiec acidsand other herbicides at the ng/ml level in wster by solid-phase extrortion withwater sample at two PCP concentrations, which were divided in 200 mlpoly ( dvinylbenzene cr syvnlyrlidone) sorbentportions and extracted by SPE and LLE methods, respectively. T1liquid chromatography- diode aroy deleetion[Jj. Journal of Chromstngraphyresults are surunarized as Table 3.A.867: 169-175.Table 3 The recovery of diferent water sample in comparison study of SPEParill P, Martiner J L V.19979. Delermination of pesticide residues in waterand LLE (%)using LLE or SPE and HPLCIDAD detection[J]. Anlytieal ltters. 30:1719-1738.Concn.= 20 148/LConen.= 200 rug/LWater sampleRaikeC，Preusnit J M，1972. Adorption of onpanie solues from diluteSPE.ueSPELEaqueous solution on GACJ]. Ind Engin (hem Fund. |1: 445- -451 。Distiled water87.67S93.8Silria L, Daniel F. Damia B, 1999 Elicient solid-phase extraction proeduresMunicipal wostewater119.58100.4107.8for trace enrichment of prioity phenols from industial eMuents with bigh totlIndustrial waslewater133.67.698.5organic carbon contentU!. Joumnal of Chromatography A. 857: 97- 106.The rcesults sthowed that there was no significant difTerence betweenVriendt CA de. Srspabroeck DK van, Rossrel M T et al.2001. Developonentand validaion of a high-perfomance liquid chromatographic nethod for thethe two extructin methods. Al the concentration level of 200 pug/I. thedeterminaion of y-hydroxybulyrir arid in ratl plasma [J ]. Joumal ofrecoveries were of 93.8% -117.6%nd 94.7%- 107.8% ,repetively, by he SPE and LLE methods. At the concentration level ofVolul中国煤化工x0 Anucoo ad de20 pug/1. the rcveres of the SPE and the LIE were 87.6% - 133.6%HC N M H Gwith clular mnd humonland 79%一120.3% , respectively.inmundeiciencieslJI. Archives of Eavironnental Health. 56: 77- - 83.Compared with ILE, SPE has several advanlages. First， thWangJ L, Qian Y, Nige! H e al.. 2000. Binadeorption of pentachlorophenol20u Ping et al.val. 16fromaqueous solution by aclivated sludge bionass[J]. Bioreoure Technology,Contain Toricol, 64: 16-19.75: 157-161.Zheug M H, Zhang B. Bao zC et al..200.0 Analysis of petclerophenol from(Reeived for reviw September 24. 2002. lccepted Oewober 11. 2002)water. sedinents,and fish hile of Dongting Lake in China!小. Bull EnvironThe Research Center for Eco-Environmental Sciences ，Chinese Academy of SciencesEnvironmental Aquatic Quality) and two CASAcademy of Sciences( RCEES/CAS), frmely Insiute of Environmental key lbarators(Key Laboralory of Environmenlal Chemisury andChemistry. Chinese Academy of Sciences, was founded in 1975. InEcotoxicology, and Key Laboralory of Systems Eecology). Research1986, it was amalgamaled with Research Center of Ecology, CAS, and Center for National Status, CAS is also at RCEES .was renamed $ Research Center for Eco- Environmental Sciences,RCEES ofers theee year M. Se. programs in environmentalChinese Academy of Sciences. Since 1996， RCEES was under thesciences, ecology ，environmental engineering. organie chemistiry andjurisdiction of both Chinese Academy of Sciences and State analytical chemistiy ,hree year Ph. D programs are ofered inEnvironmental Protetion Administration. The main research areas of enironnental sciences， environmental engineering. and ecology. andRCEES include cnvironmental chemistly ，environnental enginering. two year postdoetoral programs are ofered in cnvironmental sciences.and systems ecology. Aiming to realie the intepenetrationRCEES has established acadermic exchanges, cooperation and jointenvironmental chemistry, environnental engineering， ecology, .student training intiatives with Germany, USA. Japan, UK. Canada,geoscience and other disciplines, RCEES is taking the advanlage of theSwitzerland. Sweden, the Netherlands ，Australia and other countries.multidisciplinany research to solve the major environmental and ecological RCEES has coopernted with national universities in ofering jointproblems alt the local, regional, national as well as gobal levels.postgraduate programs and carrying out joint research projects. The jointSince 1975，RCEES hus earried out a large nunber of nesearchonganizations established by RCEES and obher units are Sino Australiaprojects granted by the central govemnent, CAS, and loceul govemunents Soil Envitonment Jaint Laboratory, Joint Insitute of Envronmentalas well amanyinternational cllaborative projects， obtaining both Sciences of RCEES and Hong Kong Bapism University. and RCEES-nationally und intemationally recognized achievements. RCEES has also Aglient Environmental Analytical Lab of Asian-Pacific Region. RCEESacted as a training center in environmental sciences and ecology in has organized many important international conferences on ecoChina. RCEES has significanly contibuted to the establishmnent and environmental sciences and pronoted the cooperation and exchangedevelopment of eco-environmental sciences and tcchnology, especially anong frign and Chinese scienists.the environmental chemisury and systems ecology in China. and ltoAdd: 18 Shuangqing Road，Haidian Districtenvironmental pollulion control and eco- environmental protection andP.0. Box 2871sustainable development in China and become a nationally leading andBeijing 100085 , Chinaintermalionally recognizred research institute in the field of eco- Tel; 86 10 62923549environmental sciences and technology .Fax: 86 10-62923563There are 308 salls in RCEES, including 3 academicians, 48esearch pfesrs. There are 8 research laboratories and one center for Website: htp://ww . rees . ac .cninformation and publication, in which there are one state key laboralory中国煤化工MYHCNMHG