Inorganic Arsenic Speciation in Groundwater Samples Using Electrothermal Atomic Spectrometry Following Selective Separation and Cloud Point Extraction

Abstract

A method has been developed for speciation of total, total inorganic and organic arsenic (As) species in groundwater samples. The inorganic species of As^(III,V) were separated from organic forms by adsorbing on alumina (Al₂O₃) whereas the organic As was eluted out. The retained inorganic As species was eluted by 0.2 M HCl. Then eluent As^III and As^V were formed as complexes with ammonium pyrrolidinedithiocarbamate (APDC) and molybdate, respectively. Then As^III-PDC and As^V-molybdate complexes were quantitatively extracted into a non-ionic surfactant Triton X-114. The total As was determined by conventional preconcentration procedures. The resulting solutions of each method were determined by ETAAS with modifier. The main factors affecting the separation and cloud point extraction (CPE) were investigated in detail. The limits of detection values were found as 0.04 and 0.20 μg L⁻¹ for As^III and As^V, respectively, whereas limits of quantification were observed as 0.13 and 0.33 μg L⁻¹ for As^III and As^V, respectively. Standard addition method confirmed the accuracy. The recoveries of As^III and As^V were found in the range of 98 – 99%. The proposed method was applied to groundwater samples collected from different areas of Sukkur district.