Department of Chemistry & Biochemistry and Southeast Environmental Research Center, Florida International University, Miami, FL 33199, United States.
J Hazard Mater. 2013 Nov 15;262:1223-9. doi: 10.1016/j.jhazmat.2012.05.043. Epub 2012 May 17.
Arsenic (As) can form complexes with dissolved organic matter (DOM), which affects the fate of arsenic in waste sites and natural environments. It remains a challenge to analyze DOM-bound As, in particular by using a direct chromatographic separation method. Size exclusion chromatography (SEC) hyphenated with UV spectrophotometer and inductively coupled plasma mass spectrometry (ICP-MS) was developed to characterize the complexation of arsenite (As(III)) with DOM. This SEC-UV-ICP-MS method is able to differentiate As(III)-DOM complexes from free As species and has the advantage of direct determination of both free and DOM-bound As(III) through mild separation. The suitability of this method for studying As(III)-DOM complexation was demonstrated by its application, in combination with the Scatchard plot and nonlinear regression of ligand binding model, for characterizing As(III) complexation with humic acid (HA) in the absence or presence of natural sand. The results suggest that, consistent with polyelectrolytic nature of HA, the As(III)-HA complexation should be accounted for by multiple classes of binding sites. By loosely classifying the binding sites into strong (S1) and weak (S2) sites, the apparent stability constants (Ks) of the resulting As-DOM complexes were calculated as logK(s1) = 6.5-7.1 while logK(s2) = 4.7-5.0.
砷（As）可以与溶解的有机物（DOM）形成配合物，这会影响砷在废物场和自然环境中的命运。分析与 DOM 结合的砷，特别是使用直接色谱分离方法，仍然是一个挑战。本文开发了与紫外分光光度计和电感耦合等离子体质谱（ICP-MS）联用的尺寸排阻色谱（SEC），以研究亚砷酸盐（As(III))与 DOM 的络合作用。这种 SEC-UV-ICP-MS 方法能够将 As(III)-DOM 配合物与游离的砷物种区分开来，并且具有通过温和分离直接测定游离和与 DOM 结合的 As(III)的优点。该方法通过与 Scatchard 图和配体结合模型的非线性回归结合，应用于研究无天然砂和有天然砂存在时腐殖酸（HA）与 As(III)的络合作用，证明了其用于研究 As(III)-DOM 络合作用的适用性。结果表明，与 HA 的聚电解质性质一致，As(III)-HA 络合作用应由多类结合位来解释。通过将结合位松散地分类为强（S1）和弱（S2）位，计算得到的 As-DOM 配合物的表观稳定常数（Ks）为 logK(s1) = 6.5-7.1，而 logK(s2) = 4.7-5.0。
