中 华 人 民 共 和 国 国 家 标 准

GB 2715─81

粮 食 卫 生 标 准               代替GBn 1─77

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1 感官指标                                                                   

  具有正常粮食的色泽及气味,不得有发霉变质现象。                             

2 理化指标                                                                    

  理化指标见下表

┌──────────────────┬────────────┐

                                      标(mg/kg)   

├──────────────────┼────────────┤

│磷化物(以PH计)(以原粮计)≤                 0.55        

├──────────────────┼────────────┤

│氰化物(以HCN计)(以原粮计) ≤             5             

├──────────────────┼────────────┤

│氯化苦(以原粮计)                         2             

├──────────────────┼────────────┤

│二硫化碳(以原粮计〕                    10               

├──────────────────┼────────────┤

│砷(以As计)(以原粮计)                 0.7             

├──────────────────┼────────────┤

│汞(以Hg计)(以成品粮计)                0.02           

├──────────────────┼────────────┤

│六六六(以成品粮计)                    0.3              

├──────────────────┼────────────┤

│滴滴涕(以成品粮良讨〕                     0.2           

├──────────────────┼────────────┤

│黄曲霉毒素B1(以成品粮计〕            按GB2761规定       

├──────────────────┼────────────┤

│七氯(以原粮计〕                           0.02          

├──────────────────┼────────────┤

│艾氏剂(以原粮计)                      0.02             

├──────────────────┼────────────┤

│狄氏剂(以原粮计)                      0.02             

└──────────────────┴────────────┘

3 七氯、艾氏剂、狄氏剂残留量测定方法                                      

3.1 气相色谱法                                                         

3.2 试剂                                                               

  使用的试剂一般为分析纯试剂。                                               

3.2.1 石油醚:30~60℃。                                          

3.2.2 乙醚。                                                         

3.2.3 硅镁型吸附剂:60~100目。取100g,于300℃高温炉中加热120min,在炉内

自然冷却后,取出加水5mL,强烈振摇至完全混匀,立即装柱使用。                                 

3.2.4 无水硫酸钠。   

                 

3.2.5 淋洗液:石油醚:乙醚=96:4。      

3.2.6 标准液:称取适量七氯、艾氏剂、狄氏剂有机氯标准品,用苯配制成储备液,

放冰箱中保存。                                       

3.2.7 标准使用液:临用时,用石油醚稀释为使用液,其浓度为七氯、艾氏剂、狄

氏剂、β─666、每毫升各相当于0.1(g,α-666、γ-666、op-DDE每毫升相当于0.2(g,

pp -DDE,pp-DDD,op-DDT,pp-DDT每毫升各相当于0.3(g。                                                                  

3.3  仪器                                                                 

3.3.1 气相色谱仪,具有电子捕获检测器。                               

3.3.2 小型粉碎机。                                                   

3.3.3 电动振荡器。                                                    

3.3.4 电水浴。                                                       

3.3.5 真空泵。                                              

3.3.6 全玻浓缩器。                                                   

3.3.7 垂熔漏斗4号。                                                  

3.3.8 柱层析管:直径1.5cm,长40cm。                         

3.3.9 色谱柱的制备:称取担体Chromosorb   WAW DMCS60~80目20g,固定液

QF─10.6g和OV─10.4g,然后将固定液用三氯甲烷;正丁醇=1:1混合液100mL冲

洗于圆底烧瓶中,在98℃水浴中加热回流使其完全溶解(3~4h),然后将担体

倒入,加热回流片刻(边加热边摇动圆底烧瓶并使担体与固定液完全混合),然

后倒入大玻璃平皿中,于红外灯下烘干,装柱后于250℃通氮气老化27h。                                       

3.4 操作方法                                                           

3.4.1 提取:称取粉碎后通过20目筛的50g样品,置于500mL锥形瓶中,加150mL

石油醚于电动振荡器上振荡60min取下,待沉淀后,将上清液倒入垂熔漏斗中,减

压过滤到全玻璃浓缩器中,然后向残渣中再加100mL石油醚振荡30min,减压过滤,

再用30mL石油醚分三次洗锥形瓶和瓶内残渣,收集全部滤液于50℃电水浴中,真空

减压浓缩至5mL。                     

3.4.3 色谱条件                                                       

3.4.3.1  Ni63电子捕获检测器                                     

  气化室温度:250℃;                                                      

  色谱柱温度:218℃;                                                     

  检测器温度:250℃;                                                     

  载气(氮气)流速:70mL/min;                                       

  脉冲供电:宽度8(s,周期100(s;                                     

  电压:30V。                                                             

3.4.3.2   色谱柱:内径3mm,长2m的玻璃柱,内装涂以2%OV-1和3% QF-1的60~80目

Chromosorb  WAW DMCS。                                             

GB 271581

3.4.3.3 测量与计算                                               

  电子捕获检测器的线性范围狭窄,为了便于定量,选择样品进样量使之适合

各组的线性范围。根据样品中七氯、艾氏剂、狄氏剂、六六六和滴滴涕存在形式,

相应地制备各组分的标准曲线,样品中的含量(X)按下式计算。                                                                                                                                                          

                       A×1000                                         

            X=───────────     

              V1                                                 

       m×────×1000                                    

             V       

 

式中:X─ 样品中七氯、艾氏剂、狄氏剂、六六六、滴滴涕及其异构体的

含量,mg/kg;    

         A─ 被测样液中七氯、艾氏剂、狄氏剂、六六六、滴滴涕的含量,ng;                                                                                  

   V─ 样品净化液体积,mL;                                              

   V1─ 样液进样体积,(L;                                               

   m─ 样品质量,g。                                                     

 

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