关键词: 砷、硒和铬形态, 微波萃取, 高效液相色谱-电感耦合等离子体串联质谱, 同步分离, 质谱干扰

Abstract: 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 (pH 7.5) 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.

Key words: species of arsenic, selenium and chromium, microwave-assisted extraction, high phase liquid chromatography-inductively coupled with plasma tandem mass spectrometry, simultaneous separation, mass spectral interference