Simultaneous determination of As, Hg, Sb, and Se in mineral fertilizers using ultrasonic extraction and CVG-ICP OES

Abstract

A method for the simultaneous determination of As, Hg, Sb and Se in fertilizers by axial view inductively coupled plasma optical emission spectrometry using on-line chemical vapor generation is proposed. The sample added with aqua regia is sonicated for 15 minutes. The concentrations of NaBH₄ and HCl used for the chemical vapor generation and plasma power were evaluated using a fertilizer sample from an interlaboratory program, which was digested in a microwave oven or sonicated in the presence of aqua regia. For a 100 mg sample, the obtained detection limits (LODs), were 0.5 μg g⁻¹ (As), 0.1 μg g⁻¹ (Hg), 1.0 μg g⁻¹ (Sb) and 0.6 μg g⁻¹ (Se). The obtained results for the standard reference material NIST 695 were in agreement with the certified values, according to the t test, for a confidence level of 95%, with the following relative standard deviation ranges: 2–5% (As), 4–9% (Hg) and 5–10% (Se). For Sb the results were adequate in comparison with that obtained by ICP-MS (inductively coupled plasma mass spectrometry), used as an independent technique. The procedure is simple and fit-for-purpose with sufficient detection power to screen for simultaneous determination of As, Hg, Sb and Se at trace levels in mineral fertilizers.