Simultaneous determination of As, Hg, Sb, Se and Sn in sediments by slurry sampling axial view inductively coupled plasma optical emission spectrometry using on-line chemical vapor generation with internal standardization

Abstract

A simple and rapid method for the simultaneous determination of As, Hg, Sb, Se and Sn in sediment slurries by axial view optical emission inductively coupled plasma using on-line chemical vapor generation and Ge(IV) as internal standard is proposed. The sample (15–30 mg with particle size ≤120 μm) is treated with aqua regia for 30 min in an ultrasonic bath. After adding 50 μg L⁻¹ of Ge(IV), the volume is made up to 15 mL with deionized water. Ge(IV) at 219.871 nm was used as the internal standard for As and Se. The concentrations of NaBH₄ and of HCl used for the chemical vapor generation were optimized by factorial analysis, using an aqueous standard solution of the analytes and a slurry of a certified sediment. Two ultrasonic systems with two different frequencies (25 kHz and 40 kHz) were tested, the more powerful one being adopted, since it provided more efficient analyte extraction to the liquid phase. The obtained detection limits (LODs), for 20 mg of sample, were: 0.5 μg g⁻¹ (As), 0.1 μg g⁻¹ (Hg), 0.2 μg g⁻¹ (Sb), 0.1 μg g⁻¹ (Se) and 6 μg g⁻¹ (Sn). The obtained results for 4 certified sediments 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: 2–11% (As), 2–4% (Hg), 4–12% (Sb), 5–15% (Se) and 3–15% (Sn), all adequate for slurry sampling.