Feasibility of quantitative inorganic arsenic speciation at the parts-per-trillion level using solid phase extraction and femtosecond laser ablation inductively coupled plasma mass spectrometry

Abstract Toxicity of arsenic compounds depends on the chemical structure as well as the concentration. Thus, separation of the toxic arsenic species should precede the quantification for the accurate toxicity assessment. Ion chromatography inductively coupled plasma mass spectrometry (IC-ICP-MS) has been the most popular method for separation and quantification of toxic arsenic species. However, the method requires complex instrument, elaborate sample preparation, and long analysis time. In this work, toxic inorganic arsenic species in water was separated by the simple solid phase extraction (SPE) using a strong anion-exchange membrane filter, and then the membrane filter was analyzed by femtosecond laser ablation inductively coupled plasma mass spectrometry (fs-LA-ICP-MS). The pH value of the sample was adjusted to 4 using ammonium hydroxide and phosphoric acid for the complete separation of the toxic inorganic arsenic from the other organic arsenics. The linear dynamic range was from 0.5 to 1000 μg/kg, and the correlation coefficient was 0.99989. The recovery efficiency was 96‑106%. The detection limit of the inorganic arsenic was 0.028 μg/kg. Our results indicate that SPE-fs-LA-ICP-MS provides enough analytical performance to analyze the toxic inorganic arsenic in water at the level of parts per trillion using the simple separation method and the rapid laser ablation sampling.