微波萃取结合高效液相色谱-电感耦合等离子体串联质谱同步分析水中砷、硒和铬形态

Simultaneous Analysis of Arsenic, Selenium and Chromium Species in Water by Microwave-Assisted ExtractionHigh Performance Liquid Chromatography-Inductively Coupled Plasma Tandem Mass Spectrometry

建立微波萃取结合高效液相色谱-电感耦合等离子体串联质谱同步分离和测定水中砷、硒和铬的9种元素形态。0.5 mmol/L EDTA(pH 7.5)缓冲液在100℃微波萃取2 min,通过Hamilton PRP-X100阴离子交换色谱进行分离。流动相用氨水调节pH 7.5,以4 mmol/L NH_4HCO_3和0.3 mol/L NH_4HCO_3分别为流动相A和B进行梯度淋洗,成功地分离了砷甜菜碱、亚砷酸根、二甲基砷酸根、一甲基砷酸根、砷酸根、亚硒酸根、硒酸根、三价铬和六价铬9种元素形态。电感耦合等离子体串联质谱具有2个独立质量筛选功能的过滤器,能够很好地消除质谱干扰,同时在不使用甲醇等有机物的情况下使用氧气与目标离子反应生成新的目标待测离子,降低了背景等效浓度,提高了灵敏度。9种元素形态检出限分别为0.023、0.056、0.032、0.064、0.061、0.091、0.089、0.21μg/L和0.18μg/L,均远低于标准限量。精密度(0.23%~11.9%)和回收率(72%~119%)良好,均满足要求。本方法的建立为食品中砷、硒和铬的元素形态分析和前处理方法提供基础研究。

A method for the simultaneous separation and determination of nine species of arsenic, selenium and chrome in water was established by microwave-assisted extraction combined with high performance liquid chromatography-inductively coupled plasma tandem mass spectrometry（HPLC-ICP-MS/MS）. Samples were extracted with 0.5 mmol/L EDTA buffer（pH7.5） at 100 ℃ for 2 min and then the extract was separated by Hamilton PRP-X100 anion exchange chromatography. The mobile phase was adjusted to pH 7.5 with aqueous ammonia for gradient elution by using 4 mmol/L NH4HCO3 as mobile phase A and 0.3 mol/L NH4HCO3 as mobile phase B. The nine element species including arsenic betaine, arsenite, dimethyl arsenate, monomethyl arsenate, arsenate, selenite, selenium, trivalent chromium and hexavalent chromium were successfully separated by the developed method. The ICP-MS instrument with two independent mass screening filters could effectively eliminate mass spectral interference. In the case where organic matters such as methanol were not used, a new target ion was generated by reacting oxygen with the target ion, thereby reducing the background equivalent concentration and improving the sensitivity. The detection limits（LODs） of the nine analytes were 0.023, 0.056, 0.032, 0.064, 0.061, 0.091, 0.089, 0.21 and 0.18 μg/L, respectively, which are well below the standard limit. This method displayed good linearity, precision（0.23%–11.9%） and recovery rate（72%–119%）, all of which meet the analytical requirements. The establishment of this method can provide a useful tool for the speciation analysis of arsenic, selenium and chrome in food.