Department of Chemistry, Faculty of Natural and Agricultural Sciences, University of Pretoria, Lynnwood Road, Pretoria, 0002, South Africa; Spectrum Central Analytical Facility, Faculty of Science, University of Johannesburg, Kingsway Road, Johannesburg, 2006, South Africa.
Department of Chemistry, Faculty of Science, University of Johannesburg, Kingsway Road, Johannesburg, 2006, South Africa; Laboratory Services Branch, Ontario Ministry of the Environment, Conservation and Parks, 125 Resources Road, Toronto, ON, M9P 3V6, Canada.
Chemosphere. 2020 Jul;250:126199. doi: 10.1016/j.chemosphere.2020.126199. Epub 2020 Feb 13.
As stand-alone approaches, chromatographic separations of arsenic in lichen using HPLC-ICP-MS or the use of sequential extractions have historically been shown to have low analyte recoveries and poor analyte selectivity respectively. This study modifies the first step of a sequential extraction with a chromatographic separation of five arsenic species using HPLC-ICP-MS, followed by a three-step sequential extraction and analysis with ICP-MS. The method was applied to lichens from a rural and urban site to demonstrate the applicability thereof, and the sum of arsenic concentrations from the extraction steps were compared to the total arsenic concentrations. Short term species stability of the As species in the lichen matrix was also evaluated over 1 month in the water-extractable fraction, where As species concentrations changed week by week, providing insight into biotransformation mechanisms. In the modified extraction step, dimethylarsinic acid (DMA) and arsenobetaine and an unknown As species (AsB + U1) were statistically (p < 0.05) higher in the urban site than the rural site. Analyte recoveries using the combined method were higher than other studies reported in literature, with percentage recoveries of 104% and 111% of As in the urban and rural sites respectively. Arsenic concentrations were found in the following order of abundance at both sites: oxidizable > reducible > water-extractable > residual. Concentrations of total As in the oxidizable and non-bioavailable fraction were statistically lower (p < 0.05) in the rural site than in the urban site. Based upon the information gained from this study, we could draw concise conclusions regarding the source apportionment, timing and the magnitude of the pollution event.
作为独立的方法，使用高效液相色谱-电感耦合等离子体质谱法（HPLC-ICP-MS）或连续提取法对地衣中的砷进行色谱分离，其分析物回收率低，分析物选择性差。本研究通过 HPLC-ICP-MS 对 5 种砷形态进行色谱分离，对连续提取的第一步进行了修改，然后用 ICP-MS 进行三步连续提取和分析。该方法应用于农村和城市地区的地衣，以证明其适用性，并将提取步骤中的砷浓度总和与总砷浓度进行比较。还在水可提取部分评估了地衣基质中砷形态的短期稳定性，在该部分，砷形态浓度每周都在变化，从而深入了解生物转化机制。在改良的提取步骤中，二甲基砷酸（DMA）、砷甜菜碱和一种未知的砷形态（AsB+U1）在城市地区的含量显著高于农村地区（p<0.05）。与文献中报道的其他研究相比，使用组合方法的分析物回收率更高，城市和农村地区的砷回收率分别为 104%和 111%。在两个地点，砷的丰度顺序如下：可氧化>可还原>可提取>残留。可氧化和不可生物利用部分的总砷浓度在农村地区显著低于城市地区（p<0.05）。根据本研究获得的信息，我们可以对地衣中砷的来源分配、时间和污染事件的严重程度得出简明的结论。
