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

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(atomic fluorescence spectrometry, AFS)与电感耦合等离子体质谱(inductively coupled plasma mass spectrometry, 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。结果显示3种前处理应用于AFS和ICP-MS测定紫菜中总As符合标准物质总As参考值范围的包括：硝酸微波消解后ICP-MS测定总砷为26.45 mg/Kg；硝酸：双氧水=3:2, V/V微波消解后ICP-MS测定总砷为27.85 mg/Kg；硫酸1.25 mL、硝酸：高氯酸=4:1, V/V湿法消解后AFS测定总砷为27.84 mg/Kg；硝酸湿法消解后ICP-MS测定总砷为24.63mg/Kg；硝酸：高氯酸=4:1, V/V湿法消解后ICP-MS测定总砷为28.04 mg/Kg；干灰化法后AFS测定总砷为27.62 mg/Kg；干灰化法后ICP-MS测定总砷为26.49mg/Kg。结论　不同的前处理方法、仪器对紫菜样品中总As的测定结果不同。3种前处理后均可用于ICP-MS测定紫菜中的总As，平均值24.63 mg/Kg ~28.04 mg/Kg，RSD2.8%~5.6%，回收率90.1%~106.5%。干灰化法平均值27.62 mg/Kg，RSD6.7%，回收率99.2%~100.9%，可用于AFS测定紫菜中总As。湿法消解采用硫酸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，RSD1.8%，回收率101.5%~105.6%；微波消解后AFS测定总As为8.92、12.31、12.25 mg/Kg，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。

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

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.