sn - 出口粮谷、蔬菜中百草枯残留量检验方法 紫外分光光度法

'SN0340-1995出口粮谷、蔬菜中百草枯残留量检验方法紫外分光光度法r~F1SiN1)0;;中华人民共和国进出口商品检验行业标准SN0340-95出口粮谷、蔬菜中百草枯残留量检验方法紫外分光光度法Methodforthedeterminationofparaquatresiduesincereals,vegetablesforexport-uv-spectrophotometricmethod1995-05-29发布1995-11-01实施中华人民共和国国家进出口商品检验局发布. 「、、ht二E生中华人民共和国进出口商品检验行业标准出口粮谷、蔬菜中百草枯残留量检验方法紫外分光光度法Methodforthedeterminationofparaquatresiduesincereals,vegetablesforexport-UV-spectrophotometricmethod1主题内容与适用范围SN0340-95本标准规定了出口粮谷、蔬菜中百草枯残留量检验的抽样、制样和紫外分光光度测定方法。 本标准适用于出口大米、白菜中百草柑残留量的检验。2抽样和制样2.1大米抽样2.1.'检验批以不超过4000袋为一检验批。同一检验批的商品应具有相同的特征，如包装、标记、产地、规格和等级等。2.'.2抽样数量按一批总袋数的平方根抽取:式中a一一抽样袋数;N一一全批袋数。注:a值取整数，小数部分向前进位为整数。2.,.3抽样工具a=.f万…(1)2.1.3.,单管取样器z不锈钢管，全长55cm(包括手柄)，直径1.5cm，沟槽长度应超过袋对角线长度的一半。 2.1.3.2取样铲。2.1.3.3分样板。2.1.3.4样品筒(袋):可密封。2.1.3.5分样布〈分样〉。2.1.4抽样方法2.1.4.1袋内抽样:按2.1.2规定计算抽样袋数(扣除倒包抽样袋数)，在堆垛四周上、中、下各部位以曲线形走向，随机抽取。将抨槽朝下，从每袋一角依斜对角方向插入皱内，将抨槽朝上旋转1800，抽出抨样器立即倒入盛样容器内。每袋抨取样品数量应基本一致。2.1.4.2倒包抽样z从堆垛的各部位随机抽取2.1.2规定的应抽样件数的10%(每批不少于3袋)，将袋口缝线全部拆开，平置于分样布或其他洁净的铺垫物上，双手紧握袋底两角提起约成45。倾斜角，倒拖1m以上，使袋内货物全部倒出后，用取样铲在各部位抨取样品约100g，立即倒入盛样容器内。中华人民共和国国家进出口商品检验局1995-05-29.批准1995-11-01实施SN0340-952.1.4.3 大样缩分:集中袋内和倒包所取样品，倒于清洁分样布上，使用分样板，按四分法缩分样品不少于4峙，加封后，标明标记并及时送实验室。2.1.5试样制备将样品缩分至1kg，全部磨碎，通过20日筛，混匀，均分成两份，装入洁净容器内，标明标记。2.1.6试样保存将试样于一5.C以下避光保存。2.2蔬菜抽样2.2.1检验批以不超过1000件为一个检验批。同一检验批内商品应具有同一特征，如包装、标记、产地、规格、等级等。2.2.2抽样数量2.2.3抽样工具2.2.3.1取样刀:不锈钢菜刀。批量，件1-2526-100101,-..,250 251-10002.2.3.2样品袋:聚乙烯塑料食品袋。2.2.4抽样方法最低抽样数，件按2.2.2规定的抽样件数，在不同部位随机抽取，逐件开启。每件抽取样品不少于500g为原始样品，原始样品总量不得少于2kg，将所取样品装入样品袋内，加封后，标明标记，及时送实验室。2.2.5试样制备将所取原始样品混匀，取可食部分，切碎，按四分法缩分出500g，经组织匀浆机匀浆成均匀的样品，均分成两份，装入洁净的广口瓶中，密封，标明标记，作为实验室样品。对于不易均匀的莱类样品，先将缩分过的样品切碎精确称重。然后将切碎的样品倒入组织匀浆机内，按样品重量的20%<m/m)加入蒸馆水，匀浆。注意z后加入的水分在称样时要扣除。上述操作的每一步都应详细记录。2.2.6试样保存将试样于一18.C冷冻保存，备用。 注z在抽样和制样的操作过程中，必须防止样品受到污染或发生残留物含量变化。3测定方法3.1方法提要试样中百草枯用硫酸溶液煮拂回流加以提取，提取液经阳离子交换树脂柱净化，百草枯被吸附在树脂上，然后，以饱和氯化锻溶液洗脱。于流出液中加入连二亚硫酸铀溶液，百草枯被还原为蓝色化合物，用紫外分光光度计进行定量。3.2试剂和材料除特殊规定外，试剂为分析纯，水为蒸馆水或相应的去离于水。3.2.1硫酸(比重1.84)。3.2.2氢氧化锅。3.2.3氯化铀。3.2.4盐酸(比重1.18)。2~ 、‘:~..>.3.2.5氯化镀。3.'2.6乙二股四乙酸二铀(EDTA)。3.2.8><#004699">7苯。3.2.8连二亚硫酸锅。3.2.9硫酸溶液:9mol/L。3.2.10盐酸溶液:2mol/L。3.2.11氢氧化铀溶液:12.5mol/L。3.2.12氢氧化锅溶液:10mol/L。3.2,13氢氧化铀溶液:0.3mol/L。SN0340-953.2.14饱和氯化铀溶液z溶解360g氯化铀于1L水中，搅拌溶解，澄清备用。3.2.15饱和氯化镀潜液:溶解3<#004699">70g氯化镀于1L於中，搅拌榕解，过滤备用。3.2.16稀氯化锻溶液:1/10饱和溶液。量取1份饱和氯化镀溶液加入9份水，混匀。3.2.1<#004699">7连二亚硫酸销溶液:0.2%于0.3mol/L氢氧化纳溶液中。溶解0.20g连二亚硫酸纳于少量 0.3mol/L的氢氧化锅潜液中，于棕色容量瓶内以该氢氧化纳榕液定容至100mL.海匀。此溶液必须在临使用前新鲜配制，超过1.5h后不宜使用。3.2.18离子交换树脂:AG50WX-6，1()0~200目，在水中浸泡。3..2.19百草枯标准品:百草枯二氧化物含量大于99%。3.2.20百草枯标准溶液z准确溶解0.0250士0.0001g百草枯标准品于少量饱和氯化镀溶液中，转移至250mL棕色容量瓶中并以饱和氯化锻溶液准确定容，摇匀，作为标准贮备液，此溶液百草枯二氯化物的浓度为100问/mLo根据需要再配成造用浓度的标准工作准。3.3仪器和设备3.3.1紫外分光光度计:具有连续波长与吸收扫描功能，配备7><5cm比色皿。3.3.2粮谷粉碎机z筛板孔径1mmo3.3.3组织匀浆机。3.3.4减压'抽滤装置:配备1000mL抽滤瓶及归Ocm平底漏斗。3.3.5加热回流装置:1000mL圆底烧瓶及配套的球形冷凝管。3.3.6净化柱:50mL酸式滴定管。在玻璃柱的下部塞入一小团玻璃棉，高度约O.5~1cm.垂直固定好柱子，加入10mL在水中浸泡并沉降的树脂，分别用50mL饱和氯化锅溶液和50mL水洗柱。注意保持液面略高于树脂层。每个试样测定均须使用一根新制备的柱子。3.4测定步骤3.4.1提取 称取粮谷试样约50.0g或蔬菜试样200.0g(精确至0.1g)置于1000mL圆底烧瓶中，根据试样.的含水量加入造量的水和9mol/L的硫酸溶液，使瓶内溶液的总体积约为200~300mL(包括试样的含水量〉、硫酸的浓度为2.5mol/L。加入数粒小玻璃珠，连接回流冷凝管。加热至沸(如产生大量气泡可加入几滴正辛醇)并使之回流5h以上。取下烧瓶，冷却，加入500mL水。将提取液倒入已铺垫好双层快速滤纸〈含油试样可多垫几层滤纸〉的平底漏斗上，用抽滤装置过滤，用少量水分数次洗涤。对非油类试样，将滤液倒入1000mL的烧杯中。对含油试样可将滤液倒入1000mL分液漏斗中，然后用100mL苯分三次萃取，收集水相于1000mL烧杯中。于烧杯中的溶液中加入12，5mol/L的氢氧化纳溶攘，其体积相当于回流前所加9mol/L硫酸溶液的量，加入5gEDTA.搅拌至完全溶解，加水至溶液总体积约900mL.然后再用10mol/L的氢氧化铺溶液调节.pH至9。冷却至室温，将溶液全部倒入1000mL的分液漏斗中备用。3.4.2净化和洗脱3.4.2.1净化3 SN0340-95将盛有提取液的分液漏斗固定在净化柱的上方(可用宿净的胶管将二者连接)，调节活塞，使溶液以10-12mL/min的速度过柱。过柱后移开分液漏斗。然后以5mL/min的速度依次用50mL水、50mL2mol/L的盐酸溶液、50mL水和50mL稀氧化锻溶液淋洗柱子，弃去所有流出液。3.4.2.2洗脱将上述处理后的柱子用饱和氧化锻溶液洗脱柱上百草枯，洗脱速度为0.5-1mL/min，收集50mL洗脱液于50mL容量瓶中。注2洗脱时柱温(环境温度〕不应低于20'C03.4.3测定3.4.3.1测定波长的选择吸取10mL含百草枯二氯化物为1.0μg/mL的百草枯标准工作液于50mL比色管中，加入2rnL连二亚硫酸铀溶液，摇匀后立即倒入<5cm比色皿中，置于紫外分光光度计比色皿中进行测定，设定波长 从410至380nm进行吸光度扫描，选择最大吸收峰处为测定波长A田，然后分别选择??m士4nm处为校正波长人和人。3.4.3.2工作曲线的绘制分别吸取百草枯标准贮备溶液0.00mL、0.05mL、0.10mL、0.25mL、0.50mL、O.<#004699">75mL、1.00mL和1.50mL于8只100mL容量瓶中，各加入饱和氯化镀溶液至刻度a此工作液百草枯的椒度分别为O.00μg/mL、0.05μg/mL、O.10μg/mL、0.25μg/mL、0.50μg/mL、O.<#004699">75μg/mL、1.00μg/m.L和1.50吨/mL。分别吸取上述工作液10mL于8支50mL比色管中，各加入2mL连二亚硫酸铀溶液，海匀后立即用紫外分光光度计，在??m处以空白液对照测定各工作液的吸光度，以吸光度为纵坐标，相应浓度为横坐标绘制标准曲线。同时于??h和λi处(与空白液对照)分别测定1.00μg/mL百草枯工作液的吸光度。3.4.3.3样品测定吸取10mL洗脱液于50mL比色管中，加入2mL连二亚硫酸铀溶液，混匀后立即于儿、儿和λl处 以空白液对照分别测定吸光度。3.4.4空白试验除不称取样品外，按上述测定步骤进行。3.5结果计算和表述按下式计算试样中百草枯(以百草枯二氯化物计)的残留量:xc.V一??m…(2)式中:X一一试样中百草枯二氧化物的残留量.mg/kg;C一一从标准曲线中以样品的校正吸:Jt度值(Ar<)查出对应的百草枯二氧化物的浓度，μg/mL;V一一洗脱液最终定容体积.mL;m一一称取的试样量.g。试样的校正吸光度值按下式计算:LP=υ.n,.n,[2A一(Ah+A1)]………........……........(3)校2A::'一(Ah+Af)L;;m式中A校一一试样的校正吸光度; 4A::'一-??m处百草枯二氯化物浓度为1μg/mL时测得的吸光度;A~一一九处百草枯二氧化物浓度为1μg/mL时测得的吸光度;Af一一λl处百草枯二氧化物浓度为1μg/mL时测得的吸光度;Am一-??m处测得试样的吸光度;Ah一-??h处测得试样的吸光度;..r:;or,,-AI一一λl处测得试样的吸光度。注2计算结果需扣除空白值。4方法的测定低限、回收率 4.1测定低限本方法测定低限为0.02mg/kg。4.2回收率SN0340-95回收率实验数据，百草枯添加浓度在0.02---10mg/kg范围内，回收率为<#004699">70.2%---108.0%。附加说明:本标准由中华人民共和国国家进出口商品检验局提出。本标准由中华人民共和国海南进出口商品检验局负责起草。本标准主要起草人欧伟、陈如娅、卓海华、张惠。主要参考文献z'FDA-PesticideAnalyticalManual,Vol.n,PesticideReg,Sec.180.205,1985.5 Prof.essionalStandardofthePeople'sRepublicofChinaforImpòrtandExportCommodityInspectionMethodforthedeterminationofparaquatresiduesincereals,vegetablesforexport-UV-spectrophotometricmethod1ScopeandfieldofapplicationSN0340-95Thisstandardspecifiesthemethodofsamp1ing,samplepreparationanddeterminationbyUV-spectrophotometryofparaquatresiduesincerealsandvegetablesforexport.ThisstandardisapplicabletothedeterminationofparaquatresiduesinriceandChinesecabbageforexport.2Samplingandsamlpepreparation 2.1Samplingofrice2.1.1InspectionlotEachinspectionlotshouldnotexceed4000bags.Thecharacteristicsofthecargowithinthesameinspectionlot,suchaspacking,mark,origin,specificationandgrade,shouldbethe'same.2.1.2QuantityofsampletakenThesquarerootofthetotalnumberofbagsinalotshallbetakenasthenumberofb??gstobesampled:wherea-Numberofbagstobetaken;N-Totalnumberofbagsinalot.a=.(万……(1)Note:Ifvalueaiswithdecimal,roundoffthedecimalpart,whichisaddedasunitytotheintegralpartofa.2.1.3Samplingtools2.1.3.1Sampler:Stainlesssteeltube.Length(inclur:linghandle)55 cm;diameter1.5cm;groovelengthismorethanhalfofthebag'sdiagonallength.2.1.3.2Samplingshovel.2.1.3.3Plateforquartering.2.1.3.4Samplecan(bag):Whichcanbesealed.2.1.3.5Clothsheet:.Forsampledividing(quartering).2.1.4Samplingprocedure2.1.4.1SamplingfromthebagApprovedbytheStateAdministrationofImportandExportCommodityInspectionofthePeople恒RepublicofChinaonMay.29,19956ImplementedfromNOV.1,199'5SN0340-95Drawthesamplesfromanumberofbagsspecifiedin2.1.2(minusthenumberofsampledbagsbyemptyingout)asfollows:Along.thesinewaveofthepile,drawsamplesfromthebagsoftheup-per,middleandlowerpartsofthepileatrandom.Insert.thesampler ,withitsgroovefacingdownward,diagonallyintoeachbag,thenturnthesamplerby1800,drawoutthesampler,andpromptlypourthesampleintoacontainer.Thequantityofthesampledrawnfromeachbagshallbebasicallythesame.2.,.4.2SamplingbyemptyingoutDraw10%ofthenumberofbagsspecifiedin2.1.2(notlessthan3bags)atanypartofthepileatrandom.Unseamandopenthebag,andlaythebagonacleanclothsheetorothercleansheet.Grasptighttwocornersofthebagbottomandraiseuptoanangleof450,tugbackwardforca1muntilallcontentofthebagisemptiedout.Scoopupthesamplefromdifferentpartsoftheout-pouredcontentwithashovel,totallingca100g,andplaceinsamplecontainerpromptly.Mixallthesamplesfromdif-ferentbagstoformagrosssample.2.,.4.3ReductionofgrosssamplePoural1thesamples(fromboth2.1.4.1and2.1.4.2)ónacleansheetforquartering,reducetonotlessthan4kgwithaplatebyquartering,placeinasamplecontainer,seal,labelandsendtothelaboratoryintime. 2.,.5PreparationoftestsampleReducethesampletoca1kg,grindthoroughlyandletpassthrougha20meshsieve,mix,divideinto2tqualportions,placeincleancontainers,sealandlabel.2.,.6-StorageoftestsampleThetestsampleshal1bestoredbelow一5.Candkeptawayfromlight.2.2Samplingofvegetables2.2.'Inspectionlot'Thequantityofaninspectionlotshouldnotbemorethan1000packages.Thecharacteristicsofthecargowithinthesameinspectionlot,suchaspacking,mark,origin,specificationandgrade,shouldbethesame.2.2.2QuantityofsampletakenNumberofpackagesineachinspectionlot1-2526-100 101-250251-1000Minimumnumberofpackagestobetaken1510152.2.3Samplingtools2.2.3.'Samplingknife:Stainlesssteelknife.2.2.3.2Samplebag:Polyethylenebagforfoodstuff.2.2.4SampleprocedureAnumberofpackagesspecifiedin2.2.2aretakenatrandomandopenedonebyone.Thesampleweighttakenastheprimarysamplefromeachpackageshouldbeatleast500g.Thetotalweightofallprimarysamplesshouldbenotlessthan2kg,whichshallbesealed,labeledandsenttolaboratoryintlme. 2.2.5PreparationoftestsampleTheedibleportionsofthecombinedprimarysampleischoppedandreducedto500gbyquarter-<#004699">7h骂一SN0340-95ing,thenblendedwith'atissueblenderanddividedintotwoequalportions.Eachportionisplacedinacleancontainerastestsample,whichisthensealedandlabeled.Forthevegetablesamplewhichishardtoblend,chopthesamplefirst,thenweighaccuratly.Transferthechoppedsamples~oablenderandaccordingtotheweightofsample,add20%(m/m)dis-tilledwater.Blenditathighspeed.Theaddedwatermustbedeductedfromtheweightofthesamplefordetermination.Eachstepmentio,nedabovemustberecordedindetail. 2.2.6StorageoftestsampleThetestsamplesshouldbestoredat-180C.Note:Inthecoutseofsamplingandsamplepreparation.precautionmustbetakentoavoidcontaminationoranyfac-torswhichmaycausethechangeofresiduecontent.3Methodofdetermination3.1PrincipleThepar,aquattestsampleisextractedwithsulfuricacidbyreflux,theextractispurifiedwithcationic'exchangeresin,thentheparaquatiselutedwithsaturatedammoniumchloridesolution.Addsodiumdithionitesolutiontotheelua旬，theparaquatisreducedresultinginacompoundofbluecol-oration,whichisdeterminedbytheUV-spectrophotometer.3.2ReagentsandmaterialsUnlessotherwisespecified,a11thereagentsshouldbeanalyticalpure,waterisdistilledwaterorcorrespondingde-ionizedwater.3.2.1Sulfllricacid(specificgravity1.84). 3.2.2Sodiumhydroxide.3.2.3Sodiumchloride.3.2.4Hydrochloricaód(specificgravityL18).3.2.5Ammoniumchloride.3.2.6Ethylenediaminetetraceticaciddisodiumsalt(EDTA).3.2.<#004699">7Benzene.3.2.8So.diumdithionite.3.2.9Sulfuricacid:9mol/L.3.2.10Hydrochloricacid:2mol/L.3.2.11Sodiumhydroxidesolution:12.5mol/L.3.2.12Sodiumhydroxidesolution:10mol/L.3.2.13Sodiumhydroxidesolution:O.3mol/L.3.2.14Saturatedsodiumchloridesolution:Dissolve360gsodiumchloridein1litreofwater,stirtodissolveandtheclearsolutionis,!;3dyforuse.3.2.15Saturatedammoniumchloridesolution:Diss??lve3<#004699">70gammoniumchloridein11itreofwater,stirtodissolveanduseafterfiltration.3.2.16Di1uteammoniumchloridesolution:1/10saturatedsolution.Add1portionoftnesaturatedammoniumchloridesolutionto9portionsofwaterandmixwell.3.,2.1<#004699">7Sodiumdithionitesolution:0.2%ino.3mol/Lsodiumhydroxidesolution.Dissolve0.20gofsodiumdithioniteinasmallpartionofo.3mol/Lsodiumhydroxidesolutionandtransfertoa100mL brownvo)umetricflask,dilutetomarkwiththeiì.8mesodiumhydroxidesolution,mixthoroughly.Pre-parejustpriortouseandnouseispermissibleafterkeepingmorethan1.5h.8-;_r.、.;-SN0340-953.2.18Cationicexchangeresin:AG50WX-8,100-200mesh,soakedinwater.3.2.19Paraquatstandard:Purityofparaquatdichlorideismorethan99%.3.2.20Paraquatstandardsolution:Dissolveo.0250士O.0001gofparaquatstandardinasmallpor-tionofsaturatedammoniumchloridesolution,transferintoa250mLbrownvolumetricflask,dilutetomarkwiththesamesolution,mixthoroughlytobeusedasastandard stocksolution,whichcontains100μg/mLofparaquatdichloride.Thendilutethesolutiontotherequiredconcentrationsasthestan-dardworkingsolutions.3.3Apparatusandequipment3.3.1UV-spectrophotometer:Withcontinuousscanfunctionforwavelengthandabsorption,e-quippedwith5cmcolorimetriccells.3.3.2Pulverizer:Thediameterofsieveapertureis1mm.3.3.3High-speedblender.3.3.4Vacuumfilterdevice:With1000mLvacuumfilterflaskand??10cmBuchnerfunnel.3.3.5Heatingandrefluxdevice:With1000mLboilingflasksandrefluxcondenser.3.3.6Cleanupcolumn:50mLburet.Putaplugofglasswoolatthebottomofcolumn,aboutO.5-1cminheight,fixthecolumnvertically,thenadd10mLofresinsoakedandsettledinwater,pass50mLofsaturatedsodiumchloridesolutionandthen50mLofwaterthroughthecolumnforwash-ing,keepthesurfaceofsolutionalittlehigherthanthesurfaceofresin.Useafreshlypreparedcolumnforeachsample.3.4Procedure 3.4.1ExtractionWeigharepresentativesampleof50.0gofthecerèalor200.0gofvegetable(allaccurateto0.1g)intoa1000mLboilingflask.Inaccordancewith.thewatercontentofthesample,addadeguateamountofwaterand9mol/LH2S04tomakeupthetotalvolumeofsolutionintheflasktoabout200-300mL(includingthecontentofsamplewater),concentrationofH2S04solutionbeing2.5mol/L.Heatunderreflux(withglassbeadsadded)toboiling(ifexcessivefoamingoccurs,addafewdropsofn-caprylalcohoDandkeepboilingforrnorethan5hours,thenremovetheflaskandletcool.thendilutewith500mLH20.FilterthesolutionthroughaBuchnerfunnelwithdoublelayersoffastfilterpaper(morelayerforoilysample)byvacunmfilterdevice,thenwashthefunnelwithwaterseveraltimes.Transferthefiltrateofthenon-oilysampletoa1000mLbeaker.Foroilsample,trans-ferthefiltratetoa1000mLseparatoryfunnel,extractthreetimeswith100mLintotalofbenzene,thentransfertheaqueousphasetoa9 SN0340-95Elutetheparaquatori.thecolumnwithsaturatedNH4ClwithaflowrateofO.5-1rnL/rnin.col-lect50rnLoftheeluateina50rnLvolurnetricflask.Note,'Columntemper.ature(roomtemperature)shouldbenotlessthan20'Cduringelution.3.4.3Deterrnination3.4.3.1Selectionofrneasuringwa:velengthPipet10rnLofthestandardsolutioncontaining1.0μg/rnLparaquatdichlorideintoa50rnLcol-orirnetrictube.add2rnLofsodiurndithionitesolution.shakewellandirnmediatelytransferthetestso-lutionintoa5cmcolorimetriccell,placeitintheUV-spectrophotometer,scanforabsorbances.atthewavelengthrangefrom410nmto380nm.Selectthewavelengthofmaximumabsorba:nceformeasur-ing(??;.)thenselectthe儿士4nmascorrectedwavelengths(..1'hand??1)respectively.3.4.3.2Preparationoftheworkingcurve Respectivelypipet0.00mL,O.05mL,0.10mL.O.25mL,O.50mL,O.<#004699">75mL,1.00mL,1.50mLofparaquatstandardstocksolutionintoeight100mLvolumetricflasks,anddilutetothemarkwithsatu'I;atedammoniumchloridesolution,mixwell.Theconcentrationoftheseparaquatstandardwork-ingsolutionareO.00μg/mL.0.05μg/mL，0.10μg/mL，0.25μg/rnL，O.50μg/mL.0.<#004699">75μg/mL.1.00μg/mL，1.50μg/mL.Respective'lypipet10mLstandardworkingsolutionsintoeight5'0mLcol-eorimetr??ctubes,add2mLofsodiumdithionitesolutionintoeachtubeandshake.Irnmediatelymeasuretheabsorbanceat??magainsttheblanksolution.Plotaworkingcurveofabsorbances(??m)(ordinateversusconcentrationsofparaquatdichloride(abscissa).Thenmeasuretheabsorbanceof1.00μg/rnLparaquatworkingsolutionat??hand??Iagainsttheblanksolution.3.4.3.3DeterminationofthetestsamplePipet10mLoftheeluatealiquotintoacolorimetrictube,add2mLofsodiumdithionitesolution,mixandimmediatelyreadtheabsorbancesat??m,??hand??Iagainst theblanksolution.3.4.4BlanktestTheoperationoftheblanktestisthesameasthatdescribedinthemethodofdetermination,butwithomissionofsampleaddition.3.5CalculationandexpressionofresultThecontentofparaquat(calculatedasparaquatdichloride)intestthesampleiscalculatedac-cordingtothefollowingformula:whereX一二主-mX-theresiduecontentofparaquatdichlorideintestsample,mg/kgI????????????.,.(2)c-theconcentrationofparaquatdichlorideintestsampleobtainedversuscorrectedabsorbance(A∞π.)fromthecalib:htioncurve，μg/mL; V-thefinalvolumeofthel:??u;，t号，rnL;m-themass'ofthetestsample,g.Note,Thecorrectedabsorbanceofthetestsampleiscalculatedaccordingtothefollowingformula,APAco口工、[2Am一(Ah+AI)JwhereAcorr.-thecorrectedabsorbanceofthetestsample;A!:,-theabsorbanceforastandardcontaining1问/mLparaquatdichlorideat??mI10…….(3)豆「.. ..~世SN0340-95A~-theabsorbanceforastandardcontaining1问/mLparaquatdichlorideat).h;Ai-theabsorbanceforastandardcontaining1问/mLparaquatdichlorideat).,;Am-theobservedabsorbanceoftestsampleat).mIAh-theobservedabsorbanceoftestsampleat).h;A,-theobservedabsorbanceoftestsampleat).,.Note:Theblankvalueshouldbesubtractedfromtheaboveresultofcalculation.4Limitofdeterminationandrecovery4.1LimitofdeterminationThelimitofdeterminationofthismethodis0.02mg/kg.4.2RecoveryAccordingtotheexperimentaldata,whenthefortifyingconcentrationofparaquatdichlorideisintherangeof0.02-10mg/悔，therecoveryis <#004699">70.2%-108.0%.Additionalexplanations:ThisstandardwasproposedbytheStateAdministrationofImportandExportCommodityIn-spectionofthePeople'sRepublicofChina.ThisstandardwasdraftedbytheHainanImportandExportCommodityInspectionBureauofthePeople'sRepublicofChina.ThisstandardwasmainlydraftedbyOuWei,ChenRuya,ZhuoHaihua,ZhangHui.Reference,FDA-PesticideAnalyticalManual,Vol.n,PesticideReg,Sec.180.205,1985.Note:ThisEnglishversion,atranslationfromtheChinesetext,issolelyforguidance.11 '