原子荧光光谱法和电感耦合等离子体质谱法测定紫菜中总砷的3种前处理方法比较

Comparison of 3 pretreatment methods for determination of total arsenic in porphyra by atomic fluorescence spectrometry and inductively coupled plasma mass spectrometry

目的比较微波消解、湿法消解、干灰化法3种前处理对原子荧光光谱法(atomicfluorescence spectrometry,AFS)与电感耦合等离子体质谱法(inductivelycoupledplasmamassspectrometry,ICP-MS)测定紫菜中总砷(As)结果的影响。方法用微波消解、湿法消解、干灰化法对紫菜标准物[总As参考值:(27±6)mg/kg]进行前处理和总砷衍生萃取,分别采用AFS与ICP-MS对总砷进行测定。结果 AFS和ICP-MS测定总砷的线性相关系数均达到0.999。经干灰化法处理,AFS测定紫菜中总As平均值为27.62mg/kg,回收率为99.2%~100.9%, RSD为6.7%;湿法消解, AFS测定采用硫酸1.25 mL、硝酸:高氯酸=4:1(V:V)此介质最为理想,总As平均值27.84 mg/kg,回收率101.5%~105.6%,相对标准偏差(relative standard deviation, RSD)为1.8%;微波消解后AFS测定总As含量范围为8.92~12.25 mg/kg。经3种前处理方法处理, ICP-MS测定紫菜中的总As平均值为24.63~28.04mg/kg,回收率90.1%~106.5%,RSD为2.8%~5.6%。结论 3种前处理方法均可用于ICP-MS测定紫菜中的总As的前处理过程。而微波消解后采用AFS进行测定,测定结果远低于紫菜成分分析标准物质中总砷的参考值范围,不适合用于测定紫菜样品中总的As。

Objective To compare the effects of microwave digestion, wet digestion and dry ashing on the determination of total arsenic(As) in laver by atomic fluorescence spectrometry(AFS) and inductively coupled plasma mass spectrometry(ICP-MS). Methods Microwave digestion, wet digestion and dry ashing methods were used to pretreat porphyra reference material [total as reference value:(27±6) mg/kg] and total arsenic was extracted by derivatization, and the total arsenic was determined by AFS and ICP-MS respectively. Results The linear correlation coefficients of AFS and ICP-MS were 0.999. After pretreating by dry ashing, the average value of As in porphyra determined by AFS was 27.62 mg/kg, the recovery was 99.2%-100.9%, and the relative standard deviation(RSD) was 6.7%;The best medium for wet digestion and AFS determination was sulfuric acid 1.25 mL,nitric acid: perchloric acid=4:1(V:V), under which condition the average value of total As was 27.84 mg/kg, the recovery rate was 101.5%-105.6%, and RSD was 1.8%;After microwave digestion, the total As content determined by AFS was 8.92-12.25 mg/kg. After three pretreatment methods, the average value of total As in porphyra determined by ICP-MS was 24.63-28.04 mg/kg, the recovery rate was 90.1%-106.5%, and RSDs were 2.8%-5.6%. Conclusion All of the three pretreatment methods can be used for the determination of total As in porphyra by ICP-MS. However, the determination results by AFS after microwave digestion are far below the reference value range of total arsenic in laver component analysis reference materials, which means the method is not suitable for the determination of total As in porphyra samples.