液相色谱-电感耦合等离子体-质谱法分析海藻碘浓缩液中砷形态

Analysis of arsenic speciation in seaweed iodine concentrate solution by liquid chromatography-inductively coupled plasma-mass spectrometry

目的建立液相色谱-电感耦合等离子体-质谱法(liquid chromatography-inductively coupled plasma-mass spectrometry,LC-ICP-MS)测定海藻碘浓缩液中6种不同形态砷化合物的分析方法。方法单因素实验确定对不同形态砷化合物LC-ICP-MS的分离条件,包括流动相浓度、洗脱方式。以总砷提取效率评价3种不同的砷化合物提取方法,确定最佳方法。结果以稀硝酸浸提的前处理方法的提取效果最佳,提取效率为84.28%~92.99%。以25 mmol/L磷酸二氢铵溶液(pH=8.0)和水作为流动相,采用梯度洗脱的方式,可以将6种砷形态完全分离。在0~100μg/L范围内,各形态砷的线性相关系数均在0.9995以上,方法检出限为0.125~0.193μg/L,定量限为0.417~0.643μg/L,平均加标回收率为80.4%~101.5%,相对标准偏差均小于5%。6种海藻碘样品中砷甜菜碱含量较多,而亚砷酸盐、砷酸盐和二甲基砷酸含量较少,未检测出砷胆碱和一甲基砷酸,样品有毒砷含量占浓缩液总砷含量的2.01%~3.69%。结论本方法准确、简单,适合海藻碘浓缩液中砷形态分析。海藻碘浓缩液中砷形态的主要存在形式为砷甜菜碱。

Objective To establish a method for determination of 6 different forms of arsenic compounds in seaweed iodine concentrate solution by liquid chromatography-inductively coupled plasma-mass spectrometry(LC-ICP-MS). Methods The single factor experiment was used to determine the separation conditions of different arsenic speciation by LC-ICP-MS, including mobile phase concentration, pH and elution mode. 3 different extraction methods were evaluated by the extraction efficiency of total arsenic, and the best method was determined. Results The pre-treatment method with dilute nitric acid extraction had the best extraction effect(84.28%-92.99%). The gradient elution was carried out with ammonium dihydrogen phosphate solution(25 mmol/L, pH=8.0) and water as mobile phase, under the conditions, 6 kinds of arsenic speciation could be separated completely. The linear correlation coefficients of each arsenic speciation were above 0.9995 in the range of 0-100 μg/L, the limits of detection were 0.125-0.193 μg/L, and the limits of quantification were 0.417-0.643 μg/L. The average recoveries of the 6 kinds of arsenic speciation were 80.4%-101.5% with relative standard deviation below 5%. The results showed that the content of arsenobetaine(AsB) in the all 6 kinds of samples were higher, while the contents of arsenite [As(Ⅲ)], arsenate [As(Ⅴ)] and dimethylarsinic acid(DMA) were less, and the arsenic speciation of arsenocholine(AsC) and methylarsonic acid(MMA) were not detected. The toxic arsenic content of the sample accounted for 2.01%-3.69% of the total arsenic content of seaweed iodine concentrate solution. Conclusion This method is accurate, simple and suitable for the analysis of arsenic speciation in seaweed iodine concentrate solution. The main arsenic speciation existed in seaweed iodine concentrate solution is AsB.