HPLC-ICP-MS联用技术研究甲醇对砷形态分析结果的影响

砷是一种有毒并致癌的化学元素，普遍存在于各种环境介质和生物体中。研究表明，砷对生物体的毒性不仅与砷的浓度，还和其存在形态密切相关。因此，对砷的不同形态进行分析具有重要意义。以往的研究表明，甲醇被广泛用作固体样品砷形态分析的提取剂，一定量的甲醇可以提高ICP-MS测总砷的信号强度。但是，关于甲醇对砷形态分析结果的影响研究尚未见报道。应用高效液相色谱-电感耦合等离子体质谱联用技术(HPLC-ICP-MS)建立同时测定AsC，AsB，As(Ⅲ)，DMA，MMA和As(Ⅴ)等六种砷形态的优化方法。HPLC采用阴离子交换柱，30 mmol·L-1 (NH₄)₂CO₃(pH=9.3)作为流动相。选择DRC模式，以O₂为反应气体，监测91AsO+作为检测信号。方法学验证表明，六种砷形态的线性相关系数都大于0.998 9。采用不同浓度的甲醇(0～100%)作为砷形态定容溶液，发现随着甲醇浓度的增加，As(Ⅲ)和DMA的峰面积显著增加。选取对砷形态结果影响最小的25%甲醇-水作为定容溶液时，其对不同浓度的砷均有一定的影响，并且对As(Ⅲ)和DMA影响最大。因此，在今后的研究中，甲醇的去除起着重要的作用。

Effects of Methanol Addition on Arsenic Speciation Analysis with HPLC-ICP-MS

Arsenic (As) is a ubiquitous, toxic and carcinogenic element, and As compounds can pose significant health risks to human and animals. The toxicity of As depends on both the total concentrations and the chemical species as well. Therefore, much attention has been paid to As speciation analysis in the environmental and biological samples. Previous studies claimed that methanol-water solvent system is one of the most frequently utilized methods for extraction of arsenic in samples, and methanol can improve As sensitivity by ICP-MS. However, the effect of methanol addition on As speciation analysis is largely unknown. In this study, the potential As speciation changes in methanol-water solvent mixture covering the range of 0~100% were investigated. Moreover, an optimized condition was employed by using high-performance liquid chromatography inductively coupled plasma mass spectrometry (HPLC-ICP-MS) for simultaneous determination of six As species including AsC, AsB, As(Ⅲ), DMA, MMA and As(Ⅴ). In accordance with previous studies, the HPLC separation was performed on anion-exchange column using a mobile phase of 30 mmol·L-1 (NH₄)₂CO₃ at pH=9.3. The ICP-MS on-line detection of As (AsO+, m/z=91) in eluting compounds was accomplished using the dynamic reaction cell (DRC) technology with oxygen as reaction gas. In addition, the method validation with optimized conditions indicated that the coefficients were above 0.998 9 for all As species. The results indicate that the peak area measured in the chromatographic signal for As(Ⅲ) and DMA increased significantly with the methanol contents, indicating significant impact of methanol contents on As speciation analysis. A test with comparison of 25% methanol solvent mixture, which showed the minimum effects on As speciation changes, and purified water, was further performed, and the results showed that As(Ⅲ) and DMA concentration increased markedly compared to those diluted by purified water but little change for the other four As species. Thus, the elimination of methanol plays an important role in As speciation analysis.