Simultaneous Voltammetric Determination of Three Herbicides in Food and Water Samples with the Aid o Simultaneous Voltammetric Determination of Three Herbicides in Food and Water Samples with the Aid o

Simultaneous Voltammetric Determination of Three Herbicides in Food and Water Samples with the Aid o

  • 期刊名字:高等学校化学研究(英文版)
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  • 论文作者:NI Yong-nian,WANG Lin,KOKOT Se
  • 作者单位:State,Department of Chemistry,School of Physical and Chemical Sciences
  • 更新时间:2020-07-08
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论文简介

CHEM. RES. CHINESE UNIVERSITES 2009, 25(2), 151- -154Simultaneous Voltammetric Determination of Three Herbicidesin Food and Water Samples with the Aid of ChemometricsNI Yong-nian'2*, WANG Lin2 and KOKOT Serge'1. State Key Laboratory of Food Science and Technology,2. Department of Chemistry, Nanchang Universil, Nanchang 330047, P. R China;3. School of Physical and Chemical Sciences, Queensland University of Technology. Brisbane 4001, AustraliaAbstract Differential pulse stipping volammetry method(DPSV) was applied to the determination of three herbi-cides, ametryn, cyanatryn, and dimethametryn. It was found that their voltammograms overlapped strongly, and it isdificult to determine these compounds individually from their mixtures. With the aid of chemometrics, classical leastsquares(CLS), principal component regression(PCR) and partial least squares(PLS), voltammogram resolution andquantitative analysis of the synthetic mixtures of the three compounds were sccessfully performed. The proposedmethod was also applied to the analysis of some real samples with satisfactory results.Keywords Herbicidal analysis; Chemometrics; Diferential pulse stripping voltammetryArticle ID 1005-9040(2009)-02-151-041 Introductioncomponents may pass through the soil and subsoil andpollute surface and ground water. Thousands of suchHerbicides are a group of artificially synthesizedcases, including several fatalities, are attributed to thesubstances used to fight weeds and improve agricul-normal agricultural use of pesticides. Ametryn, cyana-tural production. However, they are generally toxic fortryn, and dimethametryn(Table 1) are three commonliving organisms and are difficult to degrade as toxicweed-killers, which were quantitatively analyzed byagents with persistent bioaccumulative efects". Thedifferential pulse stripping voltammetry(DPSV) me-use of pesticides also constitutes a risk for water qua-thod in this study.lity in agricultural areas owing to the fact that theseTable 1 Chemical structures of three herbicidesHerbicidesMolecular formulaMassStructureAmetrynCHnNsS227.2$CH(CH)HCHN--NHCH2CH,CyanatrynCHpN,Cl226.5CH,HN- tw上-NHC(CH)2C=NDimchanetrynCnHnINsS255.2SCH,CH,CH,HN- t上-NHCH(CH)CH(CH)Various methods have been developed in the lastthods have not been satisfactory, in general, owing tofew years for the determination of pesticides. Most ofthe thermal instability of the molecules of these com-these are based on a separation by gas'2l and liquidpounds', and S- or P-detectors are generally required,chromatography5), and capillary electrochromatogra-for high performance liquid chromatography(HPLC);phyl4. The classical gas chromatographic(GC) me-UV or electrochemical detectors are utilized in the*Corresponding author. E-mail: ynni@ncu.cdu.cn中国煤化工Received Apirl 7, 2008; accepted May 9, 2008.Supported by the National Natural Science Foundation of China(NqMHC N M H GFoundation of JiangxiProvince, China(No. 0620041), the State Key Laboratory of the Chemo/Biosensing and Chemometrics of Hunan University, Chi-na(No. 2005-22) and the Program for Changjiang Scholars and Innovative Research Team in Uniersities of China(No. IRT0540).152CHEM. RES. CHINESE UNIVERSITIESVo1.25analyses of water samples from different origins asvoltammetric measurement; the three-electrode cellwell as that of samples from soils and oils. However,contained a hanging mercury drop electrode(HMDE)the usual detectors cannot provide enough sensitivityas the working electrode, an Ag-AgC(BAS MF2020)to analyze the herbicidal compounds in these samples.reference electrode, and a platinum wire auxiliaryThus, it is an appropriate objective to strive for theelectrode. pH measurements were performed on andevelopment of reliable and fit-for-purpose methodsOrion SA 720 pH meter equipped with an Ag-AgClof analysis for mixtures. Differential pulse strippingglass combination pH electrode. All experiments werevoltammetry(DPSV) provides high sensitivity to thecarried out at 25 °C.analysis, and application of chemometrics facilitatesthe resolution of overlapping signals from similar3.2 Reagentsanalytes and enables one to predict the desired pro-Ametryn, cyanatryn, and dimethametryn wereperty of the compounds.obtained from Shanghai Reagent Co., China. Stocksolutions of each of the herbicides(100 ug/mL) were2 Chemometrics Methodsprepared by dissolving the crystal of the compound inIn electrochemical techniques such as DPSV, the50 mL ethanol and were diluted to 100 mL with dis-measured current ij at a given potential is proportionaltilled water. Standard solutions(5.0 μg/mL) of theseto the analyte concentration over a given concentra-herbicides or their mixtures were then diluted to thetion range. Thus, in the absence of interactions be-required concentrations with distilled water. Atween the different components of a mixture of n elec-Briton-Robinson(B-R) buffer of pH 6.72 was pre-troactive species,pared by adding 80.0 mL of 0.2 mol/L sodium hy-droxide solution into 100 mL of a mixed acid, con-ij=koy+2 kyc;+ey (=I, 2,“",s)(1)taining 0.04 mol/L of each of boric, orho-phosphoric,and acetic acids. All chemicals were of analytical-where, ky is the proportional cofficient for compo-reagent grade and distilled water was used throughoutnent i at potential point j(total s points are selected)the experiments.and koy is the corresponding background. Let Co= 1and merge koy into the main term; Eq.(1) can further be3.3 Proceduresimply written as:A suitable amount of each herbicidal solution orkycite, (=1, 2, .,s)(2)their mixture, together with 2.0 mL pH 6.72 B-R buf-fer were transferred to an electrochemical cell andIf m standard samples are prepared, Eq.(2) can bediluted to 10.0 mL with distilled water. This solutionextended and expressed in matrix form:was purged by purified nitrogen gas for 400 s. After a(3)deposition time of 50 s and a stand period of 5 s,where, the first row in matrix K represents the back-DPSV scan was run from - -500 to- -850 mV at theground vector. According to this equation, it is possi-HMDE with a scan rate of 20 mV/s. Voltammetricble to determine the cormponents individually by sui-curves of each herbicidal compound and their mix-table chemometrics methods. In this study, the elec-tures(Fig.1) show the peak potentials for ametryn,trochemical data were treated by multivariate calibra-Misturetion methods, such as classical least squares(CLS),partial least squares(PLS), and principal component50DimehametrynCyanatynregression(PCR). The theory and application of allthese methods are well documented in the literatures[6- -9].3 Experimental0中国煤化工800 8503.1 ApparatusCNMHGvoltammograns ofer of pH 6.72A BAS 100 B/W electroanalyser(BAS) equippedp(Ametrym)=0.02 ug/mL, p(dimethametrym)-0.04 ug/mL,with a PAR 303A cell stand(EG&G) was used forp(cyanatryn)=0.03 ug/mL.No.2NI Yong-nian et al.153cyanatryn, dimethametryn at about - 655, -742, anddetermine ametryn, cyanatryn, and dimethametryn in-700 mV, respectively, as well as the heavily over-mixtures, a calibration set for multicomponent analy-lapped nature of the composite voltammogram of thesis was prepared according to a four-level orthogonalmixture.design array, denoted by 0A16(45)"0. The voltammo-grams of these samples were measured and processed4 Results and Discussionby CLS, PCR, and PLS, and three chemometrics4.1 Chemometrics Calibration Modelsmodels were established. To verify the ability of theseThe calibration plots for each herbicide based onmodels, a prediction set of sixteen mixtures was pre-pared and submitted to these models to estimate thethe linear dependence of peak current on concentra-concentration of each herbicide. The results weretion are shown in Fig.2, and the parameters are sum-evaluated by total relative prediction error(RPEr) andmarized in Table 2. The results clearly indicate thatsingle relative prediction error(RPEs) criterion'. Thethe proposed DPSV method is reliable for the deter-prediction results are summarized in Table 3. PCR andmination of mixtural herbicides. It can be found thatPLS models are known to accommodate some degreethe linear concentration ranges for ametryn, cyanatryn,of non-linearity of the analytical responses, therefore,and dimethametryn are 0.01- -0.10, 0.01- -0.10, andit is general that they reflect more excellent accuracy0.01- -0.16 μg/mL, respectively, and the LOD valuesand precision than CLS.for these compounds are 0.003, 0.004, and 0.004μg/mL, respectively. Moreover, to simultaneously[(A)600[(B)80[(C)400tE 5o莒30E 402010500 600 700 800600 700 800 900500 600 700 800 900-E/mVFig.2 Voltammograms of herbicidal compounds as a function of concentration(ug/mL)(A)Ametryn; (B) dimethametry; (C) cyanaty. p/(ugmL"): (A) and (B)a. 0; b.0.01; c.0.02; d.0.03; e.0.04:;f. 0.05;g.0.06; h.0.07; i. 0.08;J.0.09; k.0.10.(C)a. 0: b. 0.01:c.0.02; d.0.04; e.0.06:f.0.08; g 0.10; h.0.12; i.0.14;j.0.16.Table2 Parameters of linear models for eachherbicidal compound4.2 Determination of three compounds in vegeta-CompoundAmetryn Dimethametryn Cyanatrynble and water samplesSample number, nVegetable and lake water samples at differentLinear range (μgmL-)0.01- -0.10 0.01- -0.10 0.01- -0.16sites were taken for analysis. A fresh commercial ve-Correlation coficient0.99900.99950.999Intercept0.940.31getable sample(mean weight 10 g) was pulverised bySlope /(nA^mL:ug')14.640.329.8a blender and was placed in a 250 mL flask. Since theSD of intercept0.030.05concentration of herbicides in vegetable samples is tooSD of slope0.540.34low for direct detection, the standard addition me-SD of equation0.04thod(spiked) was used here and each of the standardLimit of detio/ugmL'y" 0.0030.004solution of the herbicides was transferred with●Limit of detection was calculated according to the method describedin reference [1150.0 mL ethanol, and 5 g anhydrous sodium sul-Table 3 Prediction results of herbicides in mixtures withphate(to remove any water) was added to the flask.different chemometrics methods(ug/mL)Activated charcoal of 0.5 g was then added to facili-RPES(%)MethodRPE/(%)tate the removal of interfering coloring matter. TheAmetrynCyanatym DimechametrmPCR (4)F5.5(103)49(101).7104)5.mixture was shaken for 30 min(Model HY-4 oscilla-PLS(4)°5.7(97)4.3(102)4.9(103)5.:samples were ex-CLS7.3(107)3.8(98)10.31108)8.tracte中国煤化工n, 25.0mL of thea Rclative prediction error(RPE) for single component; b. RPE fortotal samples; c. values in the parentheses corespond to the number ofethan:ITH.C N M H Gn evaporating dish,factors used; d the values in parentheses correspond to the mean reco-and reduced by flowing nitrogen gas in a draughtvery(%). Recovery(%)F 100x(Cromor cisesCcAueal.chamber to 5 mL. This aliquot was diluted to 10 mL154CHEM. RES. CHINESE UNIVERSITIESVol.25with ditilled water. Then, 0.1 mL of the extract was Table 4 shows the contents of the herbicides found intransferred to the electrochemical cell for analysis.the vegetable and water samples. The procedure wasThe PLS calibration model was selected for the analy-further validated by standard addition of the three her-sis of the vegetable extracts and water samples be-bicides.cause this method was clearly superior to the others.Table 4 Determination of three herbicides in commercial vegetable and water samples by PLSFound(ug')Added(ugg~)Found ater added/(ug')Recovery(%)SamplesAM"DI_AMCY_DIDI_CSpinach'0.031 0.022 ND 0.030 0.0300.0300.062 0.053 0.03210210Celery'0.025ND0.061 0.0300.054 0.029 0.092989Cabbage'NI0.0220.0290.0280.053Sample-1"0.0500.0870.048 .Sample-2eND 0.021 0.050 0.0500.047 0.049 0.072Sample-380.0650.043 0.0320.0940.081__ 0.11291a. AM, CY. and DI represent ametryn, cyanatryn, and dimehametryn, respectively; b. purchased from Mall of Rianbow, Nanchang: c. water samplessampled from Qingshan Lake, Yaohu Lake, and Qianhu Lake, respectively.mixtures,5 ConclusionsIn this study, a DPSV method was developed forReferencesthe simultaneous analysis of the herbicides of ametryn,[川] Diaz M. C, Grrido s, Hidalgo R, Contamination Difusa, MOPU,Madrid, 1988cyanatryn, and dimethametryn. Since the voltammo-2] Maria Dolores H, Ana A, Amadeo R F. A.. et al, Analysr, 2001,gram of the mixture was a composite of the heavily126, 46overlapping voltammograms from the individual her-3] WangJ. H, Wang G. T, Yuan s. M. Chin J Anal. lab, 1999. 18,bicides, it was necessary to use chemometrics me-thods, such as CLS, PCR, and PLS. PLS calibration4] WuX. P. Wang L, Xie Z. H, et al, Chem. Res. Chinese Universities,2007, 23(1), 109models significantly improved the prediction results5] MagllonaE. D. Res. Rev, 1975. s6.1for the temary mixtures, and yielded good RPE valuesI6] Oto M.. Wegecheider W, Anal. Chem. 1985. s7, 63within 10% for both the individual and overall esti-[7] Becbe K. R., Kowalski B. R, Anal. Chem, 1987. 59. 1007Amates as well as good recoveries. The DPSV method8] Thomas E. V. Haaland D. M. Anal. Chem, 1990, 62. 1091was applied sucessfully to the analysis of the herbi-[9| Gcladi P. Kowalski B. R., Anal. Chim. Acta, 1986. 185,1cidal residues from farm vegetables and water samples;[10] Lan W. G, Wong M. K, Chen N,, et al, Analyst, 1995. 120, 111[川] Miler J. N, Miller J. C, Salistis and Chemometrics for Anabyticalthe reliability of the method was supported by goodChemistiy, 4th Ed, Pearson Education Limited, London, 2000, 122recoveries from standard additions of herbicides中国煤化工MYHCNMHG

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