大米中无机砷测定方法的研究

目的通过比较不同浓度三氟乙酸(TFA)溶液和在不同提取时间下TFA对于标准参考物质(SRM1568a rice flour)中无机砷化合物的提取能力,优化TFA溶液的浓度和提取时间,提出大米中无机砷测定方法。同时采集不同原产地的大米样品,评价无机砷污染状况。方法加入TFA,热浸提后取上清液离心浓缩至干,以流动相超声复溶,过RP柱和滤膜后进样;1mmol/L磷酸二氢铵溶液(pH9.0)和20mmol/L磷酸二氢铵溶液(pH8.0)为流动相梯度洗脱,采用Hamilton PRPX-100阴离子交换柱分离,液相色谱-原子荧光光谱法(LC-AFS)测定。结果采用3%(V/V)TFA溶液对SRM1568a热浸提2h的样品前处理方法,其测定结果符合无机砷参考值。结论方法适用于大米中无机砷的测定。所采集大米样品的无机砷含量均未超出卫生标准。

Determination of inorganic arsenic in rice by liquid chromatography-atomic fluorescence spectrometry

Objective To develop a method for the determination of inorganic arsenic(Asi) in rice and to provide the basis for revising the national standard method GB /T 5009.11 "Determination of Inorganic Arsenic in Food".To compare the extracting ability of trifluoroacetic acid(TFA) under different concentrations and the different time for extracting samples.To evaluate the pollution of rice sampling from different original production places.Methods Inorganic arsenic of rice was extracted under heating at 80℃ by trifluoroacetic acid.The supernatant was concentrated to dryness by centrifuging,and then dissolved in the solution for mobile phase by ultrasonication.Passed through RP cartridge and filter,the sample solutions were ready for analysis.The mobile phases were 1mmol /L NH4 H2 PO4 solution and 20mmol /L NH4 H2 PO4 solution.As were separated with an anion exchange column,Hamilton PRPX-100,and detected by liquid chromatography-atomic fluorescence spectrometry(LC-AFS).Results Extraction with 3% TFA(v/v) and heating for 2h were desirable for the pre-treatment of samples.The results meet the reference value of As.Conclusion This method is suitable for the analysis of inorganic arsenic in rice.The inorganic arsenic content of samples collected from original production places did not exceed the limit standard.