Abstract
Background: Arsenic is widely known as a toxic element and can cause adverse health effects. The determination of total arsenic does not indicate the level of their actual hazard. Therefore, the speciation analysis of arsenic is more significant than the determination of total arsenic concentration. We propose the use of trimethyl aminopropyl-silica-based SPE column which is commercially available and a simple chemical modification of this silica-based SPE column for the speciation analysis of arsenic (arsenite, arsenate and DMA).
Methods: A two-column system including trimethyl aminopropyl-silica column (Si-Cl) and silver chloride- silica column (Si-AgCl) was used for the separation of arsenic species. Arsenic concentrations were analyzed by an ICP-OES spectrometer. The pH of solution, flow rate, eluent concentration and sample concentration were studied for assessing optimal conditions. Results: AsV could be adsorbed on the Si-Cl column at pH 7 and was consequently eluted by 1 mol/L HCl. Inorganic arsenic species (AsIII and AsV) were retained on the Si-AgCl column at pH 9, while DMA was passed through the column. The amount of AsIII was calculated from the subtraction of AsV and DMA from the total arsenic concentration. The method detection limits of AsIII, AsV and DMA were 2.30, 1.48, and 2.51 µg/L, respectively. The recoveries and relative standard deviations of AsIII, AsV and DMA were in the range of 97.2-104.3% and 0.72-2.56%, respectively. Conclusion: The solid phase extraction method of the separation inorganic arsenic (arsenite or AsIII and arsenate or AsV) and dimethyl arsenic acid (DMA) using strong anion exchange silica and silver chloride modified silica columns was successfully developed and validated. The proposed method was successfully applied for the speciation analysis of arsenic in real industrial wastewater.Keywords: Speciation, arsenite, arsenate, dimethylarsenic acid, silica-based column, ICP-OES.
Graphical Abstract
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