Yan X P, Kerrich R, Hendry M J
Department of Geological Sciences, University of Saskatchewan, Saskatoon, Canada.
Anal Chem. 1998 Nov 15;70(22):4736-42. doi: 10.1021/ac980654e.
A method has been developed for determination of (ultra)trace amounts of As(III) and As(V) in water by flow injection on-line sorption preconcentration and separation coupled with inductively coupled plasma mass spectrometry (ICPMS) using a knotted reactor (KR). The determination of As(III) was achieved by selective formation of the As(III)-pyrrolidine dithiocarbamate complex over a sample acidity range of 0.01-0.7 mol L-1 HNO3, its adsorption onto the inner walls of the KR made from 150-cm-long, 0.5-mm-i.d. PTFE tubing, elution with 1 mol L-1 HNO3, and detection by ICPMS. Total inorganic arsenic was determined after prereduction of As(V) to As(III) in a 1% (m/v) L-cysteine-0.03 mol L-1 HNO3 media. The concentration of As(V) was calculated by difference (the total inorganic arsenic and As(III)). Owing to the group-specific character of the chelating agent, and the use of an efficient rinsing step before elution, the interferences encountered in conventional ICPMS from common major matrix, alkali and alkaline earth metals, and chlorides were eliminated. The presence of organoarsenic species such as monomethylarsonate and dimethylarsinate in water samples had no effect on the results of As(III) and As(V). Thus, the method can be applied to the speciation analysis of inorganic arsenic at submicrogram per liter levels in aqueous solutions with high total content of dissolved solid and/or high content of chlorides. Using a preconcentration time of 60 s and a sample flow rate of 5 mL min-1, an enhancement factor of 22 was achieved in comparison with conventional ICPMS. The time required for a single determination was 200 s. The detection limits (3s) was evaluated to be 0.021 microgram L-1 for As(III) and 0.029 microgram L-1 for total inorganic arsenic. The precision for 14 replicate determinations of 1 microgram L-1 As(III) was 2.8% (RSD) with drift correction and 3.9% (RSD) without drift correction. The concentrations of As(III) and As(V) in synthetic mixtures obtained by the present method were in good agreement with expected values. Results obtained by the proposed method for total arsenic in a river water reference material agreed well with certified and recently reevaluated values. The method was also applied to the speciation analysis of inorganic arsenic in porewaters.
已开发出一种方法，通过流动注射在线吸附预富集和分离，结合电感耦合等离子体质谱法（ICPMS），使用打结反应器（KR）来测定水中（超）痕量的As(III)和As(V)。在0.01 - 0.7 mol L-1 HNO3的样品酸度范围内，通过选择性形成As(III)-吡咯烷二硫代氨基甲酸盐络合物来测定As(III)，该络合物吸附在由150 cm长、内径0.5 mm的聚四氟乙烯（PTFE）管制成的KR内壁上，用1 mol L-1 HNO3洗脱，然后用ICPMS检测。在1%（m/v）L-半胱氨酸 - 0.03 mol L-1 HNO3介质中将As(V)预还原为As(III)后，测定总无机砷。As(V)的浓度通过差值计算（总无机砷和As(III)）。由于螯合剂的基团特异性，以及在洗脱前使用了有效的冲洗步骤，消除了传统ICPMS中常见主要基体、碱金属、碱土金属和氯化物的干扰。水样中有机砷物种如一甲基胂酸和二甲基胂酸的存在对As(III)和As(V)的测定结果没有影响。因此，该方法可应用于溶解固体总含量高和/或氯化物含量高的水溶液中亚微克每升水平的无机砷形态分析。使用60 s的预富集时间和5 mL min-1的样品流速，与传统ICPMS相比，富集因子达到了22。单次测定所需时间为200 s。As(III)的检测限（3s）评估为0.021微克 L-1，总无机砷的检测限为0.029微克 L-1。对1微克 L-1 As(III)进行14次重复测定，有漂移校正时的精密度为2.8%（相对标准偏差），无漂移校正时为3.9%（相对标准偏差）。通过本方法获得的合成混合物中As(III)和As(V)的浓度与预期值高度一致。用所提方法测定河水标准物质中总砷的结果与认定值和最近重新评估的值吻合良好。该方法还应用于孔隙水中无机砷的形态分析。
