中华人民共和国出入境检验检疫行业标准SN/T 1541—2005
出茶叶中二硫代氨基甲酸酯
总残留量检验方法
Inspection of the total residues of dithiocarbamatepesticides in tea for export2005-02-17 发布
中华入民共和国
国家质量监督检验检疫总局
2005-07-01实施
本标准的附录A为资料性附录。
本标准由国家认证认可监督管理委员会提出并归口。本标摊起草单位：中华人民共和国厦门出入境检验检疫局。本标准主要起草人：陈鹭平、邹伟、吴敏，周昱。本标准系首次发布的山入境检验检疫行业标准SN/T1541--2005
出口茶叶中二硫代氨基甲酸酯
总残留量检验方法
SN/T154.1—2005
本标推规定了出口茶叶中二蔬代氧基甲酸总残留量检验的抽样、制样和气相色谱测定方法。本标准适用于山口茶叶中二硫代氮基甲酸酯类农药如福美双、美锌、福美铁、代森锌、代森钠等的总残量的检验。
2抽样和制样
2.1检验批
以不超过2000件为一检验批，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抽样数避
抽样数量见1。
表 1 插样数量
51~500
501---1000
1001--1500
15012000
2.3抽样工具
a）取样句；
h）塑料布：
）分样板；
d）盛样器：可密挝的样品筒或聚乙烯塑料装。2.4抽样方法
最低描样数量
单位为件
从整批产品堆垛的不同部位随机抽取2.2规定件数的茶叶，逐件开启并倒出件内茶叶，分别骨于聚乙烯塑料布上。用取样铲取代表性样品，每件约取500g。集中并充分混匀样品，用四分法反复缩分至约500g。将样品装入清洁、于燥的样品简内，密封，并标明标记：及时送实验室。2.5试样制备
将取回的样品磨细至全部通过20自筛，混勾，均分成两份，分别装入洁净容器内：作为试样，密封，标明标记。
2.6试样保存
将试样保存于4℃以下、避光保存。在抽样和制的操作过程中，应防止样品受到污染或发生残留物含量的变化。SN/T 1541—2005
3测定方法
3，1方法提要
试样在密闭系统中与还原性酸溶液反应，含二硫代氨基甲酸酯的物资被分解，定量释放出二硫化碳，取反应液上方气体用气相色增法测定二硫化碳含量，外标法定量3.2试剂和材料
除特殊注明外，所有试剂均为分析纯，永为蒸馏水，3.2.1丙酮：经重蒸馏
3.2.2浓盐酸。
3.2.3二硫化碳标准品：纯度299%。3.2. 4 氢化亚锡(SC2H,0)。
3.2.5抗坏血酸(维生素C)。
3.2.6二硫化碳标准溶液：准确称取适量的二硫化碳（3.2.3)，用丙酮（3.2.1）稀释成浓度为1.0mg/mL的标准储备液，根据需要，再用内酮(3.2.1)稀释到适当浓度的标准工作液3.2.7氯化亚锡溶液：溶解15g氟化亚镊（3.2.4）于430mL浓盐酸（3.2.2）中，用蒸馏水稀释至1 000 mL.
3.3仪器和设备
3.3.1配有电子俘获检测器的气相色谱仪。3. 3.2 项空瓶;250 mL。
.3.3.3气密性注射器：100μL.
3.3.4烘箱。
3.4测定步骤
3. 4. 1试样前处理
称取5.0g试样于250mL顶空瓶中，加入0.3g抗坏而酸（3.2.5），再如人80mL氯化亚锡溶液（3.2.7)，立即封闭瓶口，置于80℃烘箱中加热2h，每隔30min振摇一次（不得将液体溅到瓶盖上）。3. 4.2测定
3.4.2. 1色谱条件
a）色谱柱，HP50+毛细管柱（50%聚二苯基甲基硅氧烷，柱长30m.内径0.53mm，膜厚1:0 μm).
b）进样口温度：140℃。
柱温度：50℃。
检测器温度：190℃。
e）载气：氮气，纯度≥99.99%，2mL/min.尾吹30mL/min。3.4.2.2色谱测定
用气密性注射器取顶空瓶内气体100，立即注入气相色增仪，与含量接近的标准二硫化碳气体的保留时间和峰面积作定性和定量比较。样品中二硫化碳的响应值应在仪器检测线性范围之内。在上述条件下，二硫化磁保留时间约为2,3min。3.4.2.3标准二硫化碳气体的制备用5mL水代替试样，加人适当体积的二硫化碳标准溶液（3.2.6)，加人0.3g抗坏血酸（3.2.5).再加入80ml.氯化亚（3.2.7），文即封闭瓶口，置于80℃烘箱中加热2h每隔30min振摇一次（不间将液体溅到瓶盖上），取山，用气密性注射器取顶空瓶内气体100μL，立即注人气相色谱仪。二化碳标准品的气相色谱图见附录A。
3.5空白试验
用5mL水代替试样，按3.4.1和3.4.2.2进行测定。3.6结果计算和表述
按色谱数据处理机或按式(1)计算试样中二硫代氨基甲酸酯残留量：X
式中，www.vv99.net
SN/T 1541—2005
X一试样中二硫代氨基甲酸酯总留含量（以二硫化碳计），单位为毫克每千克（mg/kg），A——样品顶空气中二硫化碳峰面积，单位为平方毫米（mm）；A一—标准项空气巾二蔬化碳峰面积，单位为平方毫米（mm\）二硫化碳标准工作溶液的浓度，单位为徽克每毫升（g/mL)；二硫化碳标准工作溶液的体积，单位为毫升（mL），样品质量，单位为克(g)。
注1:计算结果需扣除空白。
注2：二硫代氨基甲酸酯含量一般以代森锌计，一分子代森锌在酸溶液中释放二分于二硫化碳，印1.81ng代森锌释放山1mg二硫化碳。
测定低限和回收率
4.1测定低限
本方法测定低限（以一硫化碳计)为0.1mg/kg4.2回收率
茶叶中福美双添加浓度及其回收率的实验数据：在0.10mg/kg时，回收率为86.7；在0.50n%/kg时，回收率为89.0%；在1.0mg/kg时，回收率为91.3%。茶叶中福美铁添加浓度及其回收率的实验数据：在0.10mg/kg时，回收率为85.6%，在0.50 mg/kg时,回收率为 97.4%;在 1. 0 mg/kg时,回收率为 89. 5%。茶叶中福美锌添加浓度及其回收率的实验数据：在0.10mg/kg时，回收率为84.5%；在0.50mg/kg时.回收率为88.7%
在 1. 0 tg/kg 时,回收率为 85.8%。茶叶中代森锌添加液度及其回收率的实验数据：在0.101g/kg吋，回收率为85.5%；在0.50mg/kg时,[叫收率为87.1%在1.0mg/kg时，回收率为86.1%。茶叶代森钠添加度及其回收率的实验数据：在0.10mg/k时，回收率为84.1%；在0.50 mz/kg时,回收率为86.8%;在1.0mg/kg时，回收率为87.7%。3
SN/T1541—2005
附录A
（资料性附录）
标准色谱图
二能化碳
时间 / min
图A.1二硫化碳标准品气相色谱图Foreword
SN/T 1541—2005
Annex A of this standard is an infarmative annex.This standard was proposed by and is under the charge of the Certificatiorn and AccreditationAdministration of thePeople'sRepublic of ChinaThis standard was drafted by Xiamen Entry-Exit Inspection and Quarantine Bureau of thePeople's Republic of China.
The main drafters of this standard are Chen Luping,Zou Wei,Wumin,and Zhou YuThis standard is a professional standard promulgated for the first time.SN/T 1541-2005
Inspection of total residues of dithiocarbamatepesticides in tea for export1
This standard specifias the miethods of sampling. sample preparation and determination of totaldithiocarbamate rasidues by gas chromatography in tea for export.This standard is applicable to the determination of total residue contents of Thiram,Ziram,Fer-bam,Zineb,Nabarm etc. in tea for export.2 'sampling and sample preparation2.1Inspection lot
Each inspection lot should not exceed 2 o0o packages.The characteristics of the cargo within the same inspection lot, such as packing,mark,origin,specification and grade,shotuld be the same.2.2. Quantity of sample takenQuantity of sampletaken is shown in table1.Quantity of sample taken
Table 1
NMumber of packag es in each inspaction lot1~5
51~500
501 ~1 000
1001~1500
1501~2000
2. 3 Sampling toolis
a)Sampling ladle
b) Plastic cloth.
Minimum number of packages to be baken2
c)Plate for quartering.
d)Sample container:Can or plasticbag,which canbe sealed.2. 4 Sampling pracedure
Draw a number of tea sample packages specified in 2. 2 from different parts of the stack at ran-dom,open the packages one by one and pour the tea on a clean plastic sheet respectively. Take upabout 50og of representative sample from each packages with a sampling shovel. Mix all the samplethoroughty ,and reduce to ca 5oog by quartering,promptly place in a clean,dry sarmple container, seal,label and send to laboratory in time.2.5 Preparation of test sampleSN/T 1541—2005
Crush the sample with a grinder and let whoily pass through a 20-mesh sieve. Mix well and di-vide into two equal portions. Each portion is placed in a clean container as the test sample, which isthen sealed and labeled.
2.6 Storage of test sample
The test samples shall be stored below 4' and kept away fram light.In the course of sampling and sample preparation,precautions must be taken to avoid contamina-tion or any factars which may cause the change of residue content,3Method of determination
3.1Principle
The substance containing dithiocarbamate residue in test sample is decomposed with deoxidi-zing acid solution in a closed container,releasing carbon disulfide guantitatively. The gas upper thereaction liquid is taken to be tested and the carbon disulfide is determined by gas chromatography u-sing external standard method.3. 2 Reagents and materials
Unless otherwise specified,all reagents are analytical pure, \water\ is distilled water.3.2.1Acetone:Redistifled.
Concentrated hydrochloride acid,Carbon disulfide standard: purity99%.Stannous chloride(SnCl·2HO).3.2.4
3. 2. §Ascorbic acid (Vitamin C). Carbon disufide standard sotution: Accurately weigh an adequate amount of carbon disuifide3.2,6
(3.2. 3),dissolve in acetone(3. 2. 1>to prepare a solution af 1. 0 mg/mL in concentration as thestandard stock solution. According to the requirement,prepare a standard working solution of appro-priate concentration by diluting the stock solution with acetone(3, 2.1).3. 2.7 Stannous chloride solution: Dissolve 15 g of stannous chloride(3. 2. 4) in 433 mL af concen-trated hydrochloric acid(3. 2. 2) and make up to 1 oao mL with water.3.3 Apparatus and equipment
Gas chromatography,equipped with electron capture detector,Head-space bottle: 250 mL.
Gas-tight syringe: 100 μL.
3.3.4Oven.
3.4Procedurg
3, 4. 1Preparation of the sampleWeigh 5, 0 g of the test sample into 250 mL head-space bottie. Add 0. 3 g ascorbic acid(3.2. 5),then add 80 mL of stannous chloride solution(3. 2.7) and close the bottle immediatelyPlace the bottle in an oven at 80'℃ for 2 hour. Shake at an interval of ca 3o min (do not splash the[iquid up to the cover).
3.4.2 Determination
3. 4. 2. 1 GC operating conditiana)Column;Hp 50tcapillary colurmn.(Crosslinked 50% Ph Me Sificone.length:30m,diameter:0. 53 mm,Film thickness; 1. 0. um. )SN/T 1541—2005
b)Injectionporttemperature：140cColumn temperature: 50c.
d) detector temperature: 190℃Carrier gas: Nitrogen,purity≥99.99% ,2 mL/min,AUx gas:30 mL/min.）
3.4.2.2Gcdetarmination
Take 1o0 μL of gas in the head-space bottle with the gas-tight syringe and inject into the gaschromatography immediately,compare qualitatively and quantitatively the retention time and peak ar-ea with that of the standard carbon disulfide gas of similar content. The respondence value of thesample shall be in the detection linear range of the instrument. The retention time of carbon disulfideis about 2. 3 min under the above mentioned conditian.3. 4. 2.3 Preparation of the standard carbon dlsulfide gasReplace the test sample with 5 mL of distilled water, add adequate volurme of carbon disulfidesolutipn(3. 2. 6), add 0. 3 g ascorbic acid(3. 2. 5), then add 8o ml of stannous chloride solution(3, 2. 7) .close the bottle irnmediately. Place the bottla in an oven at 80'C for 2 h,Shake at an intervalof ca 30 min (do not splash the liquid up to the cover). Take 10o μL of gas in the head-space bottlewith the gas-tight syringe and inject into the gas chrormatography immediatety. The gas chromato-gram of carbon disulfide standard is shown in annex A,3. 5 Blank test
Carry out the procedure described in 3: 4. 1 and 3. 4. 2. 2, while the test sample is replaced with5 mL of water.
3.6Calculation and expression of the resultCalculate the dithiocarbamate residue content in the test sample by data processor or accordingto formula (1) :
（1）
Where:
-the total content of dithiocarbamate residue (calculated as carbon disulfide) in the testX
sample.mg/kg:
-the peak area of carbon disulfide in the sample bottle,mm? :44
-the peak area of carbon disuifide in the standard bottle, mm? :the concentration of carbon cisulfide in the standard working solution. μg/mL;-the volumie of the standard working solution,mL:m ---the mass of the test sample,g.Note; The blank vaitue should be subtracted from the above result of calculation.4Limit of determination and recovery4. 1 Limit of detemnination
The limit of detemination af thls method is 0. 1 mg/kg (as carbon disulfide).4.2Recovery
According to the experimental data,the fortified concentrations of thiram in tea and its corre-sponding recoveriesare:
0. 10 mg/kg,the recovery 86. 7% 8
D. 50 mg/ kg, the recavery 89, 0% ;1. 0 mg/kg, the recovery 91. 3%.SN/T1541—2005
Acoording to the experimental data, the fortified concentrations of ferbarh in tea and its corresponding recoveries are:
0.10 mg/kg,the recovery 85.6%;0. 50 mg/kg, the recovery 91. 4% ;1.0 mg/kg , the recovery 89. 5%,According to the experimental data, the fortified concentrations of ziram in tea and its corre-sponding recoveries are :
0. 10 mg/kg, the recovery 84. 5% ,0.50mg/kg.therecovery88.7%;
1. D mg/kg,the recovery 85. 8%According to the exparimental data, the fortified concentrations of zineb in tea ard its corre-sponding recoveries are:
0. 10 mg/kg,the recovery 85.5% ;0. 50 mg/kg, the recovery 87. 4% [1. 0 mg/kg, the recovery 86. 1%.According to the experimental data, the fortified concentrations of nabam in tea and its corre-sponding recoveries are:
0. 10 mg/kg , the recovery 84. 1% :0.50 mg/kg,the recovery 86.8%,1. 0 mg/kg, the recovery B7. 7%.SN/T1541-2005
Oniea asuudssd
AnnexA
(informative?
Chromatogramofthestandard
caubon diglfide
Gas chromatogram of carbon disulfide standard
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