硅镁吸附剂:60~100目,550℃灼烧5h,以5%水减活化,混匀,放置2天以上。用前于130℃烘2h,以5%水减活化,平衡过夜后使用; 稻瘟灵标准溶液:准确称取稻瘟灵标准品(纯度≥97.5%),用丙酮配制成1.0mg/mL的标准储备液,冰箱保存。临用时用丙酮稀释成1.0μg/mL的标准使用液。 Silicon-magnesium adsorbent: 60-100 mesh, burned at 550℃ for 5 hours, deactivated by 5% water, mixed well, lay aside for at least 2 days, burned at 130℃ for 2 hours before use, deactivated by 5% water, lay aside over night. Isoprothiolane standard sample solution: weigh accurately certain amount of isoprothiolane standard sample (purity not lower than 97.5%), prepare a standard stock solution using acetone, store in refrigeratory. Prepare a standard sample solution with concentration of 1.0 μg/ml using use this stock solution to when test.
3.1 Extraction Weigh 20g of rice sample grinded and passed the 20 mesh sieve to a flask with stopper, add 50 ml of acetone, shake for 30 minutes by the electrodynamic shaker, filter to a beaker through quick qualitative filter paper, extract the residue once more using the above method by 30 ml of acetone. Wash the residue by 30 ml of acetone in several times, combine the washings to a beaker, vaporize to dry on the water bath of 50℃.
3.2.1 Preparation of column Insert 2 cm of anhydrous sodium sulfate in the bottom of the column ( Φ20mm x200mm), pack 10 g of silicon-magnesium adsorbent into the column, pack 2 cm of anhydrous sodium sulfate in the upside of the column. Elute by 20 ml of dichloromethane, discard the eluate.
4.2.2.样品提取液的净化 用少量二氯甲烷溶解样品提取浓缩液,倾入层析柱。用100mL二氯甲烷洗脱,洗脱速度为0.5~1.0mL/min。收集洗脱液于K.D浓缩器中,减压浓缩至1.0mL以下。用丙酮洗涤K.D浓缩器继续浓缩至1.0mL以下。最后用丙酮定容至1.0mL,待测。 3.2.2 Purification of the extract Dissolve the concentration of the extract by little amount of dichloromethane and pour into the column. Elute using 100ml of dichloromethane with a speed of 0.5~1.0mL/min. Collect the eluate to the K.D. concentrator, concentrate by reducing the pressure until the volume is lower than 1.0 ml, wash the K.D. concentrator using acetone, continue to concentrate volume is lower than 1.0 ml. Make up to volume of 1.0 ml using acetone.
4.测定 吸取稻瘟灵标准使用液和样品净化液各1.0μL,分别重复3次测定。以保留时间定性,以样品的平均峰高值与标准的平均峰高值比较定量。在上述色谱条件下,稻瘟灵的保留时间约为2.6min。 3.4 Determination Pipette 1.0 μl of the standard solution and 1.0 μl of the test solution respectively, and repeat the determination for three times. Qualify by the retention time, quantify by comparing the average peak height of the test sample and the standard sample. The retention time of isoprothiolane is 2.6min under the above chromatographic conditions.
4.1 Calculation The square of the concentration of sulfur in isoprothiolane is in the direct ration with the peak height at the wave length of 394nm when using FPD. When the injected volume of standard solution is the same as the test solution, the concentration of isoprothiolane in the test sample is calculated by the followed formula:
Ci2= Cs2×hi ……………………………(1) hs where: Ci——Concentration of isoprothiolane in the test solution, g/mL; Cs——concentration of isoprothiolane in the standard solution,μg/mL; hi——Peak height of isoprothiolane in the test solution, mm or mV; hs——Peak height of isoprithiolane in the standard solution, mm或mV。 The concentration of isoprothiolane in the test sample is calculated by the followed formula: X= Ci×Vi …………………………(2) m Where: X——Isoprothiolane content in the test sample,mg/kg; Vi——Final volume of the test solution,mL; m——Mass of the test sample,g。
5. Allowance 本标准检出限为0.26ng,若取20.0g大米样品,其最低检出浓度为0.013mg/kg;标准曲线的线性范围为0~15ng;平均添加回收率为108.4%;相对标准偏差≤10%。 The detect limit is 0.26mg. The lowest concentration detectable should be 0.013mg/kg if the amount of the rice sample is 2.0 g. The linear of the standard curve is0-15 mg; the average spiked recovery is 108.4%, and the relative standard deviation is not greater than 10%.