Correction of structured molecular background by means of high-resolution continuum source electrothermal atomic absorption spectrometry—Determination of antimony in sediment reference materials using direct solid sampling

A simple, fast and accurate procedure is proposed for the determination of antimony in certified sediment reference materials using direct solid sampling high-resolution continuum source electrothermal atomic absorption spectrometry and iridium as a permanent modifier. The less sensitive resonance line at 231.147 nm has been used in order to allow the introduction of larger sample mass. Six certified reference materials, one river, one estuarine and four marine sediments have been analyzed. The use of iridium as a permanent modifier caused an increase of 30% in sensitivity and stabilized antimony in the sediment to a pyrolysis temperature of 1100 °C. Significant background absorption with pronounced rotational fine structure was observed at the optimum atomization temperature of 2100 °C, which coincided with the analyte atomic absorption in time. This background was found to be due to the electron excitation spectra of mostly the SiO and in part the PO molecules, and could be eliminated by applying a least-squares background correction algorithm. A characteristic mass of 28 pg Sb was obtained, and the limit of detection (3σ, n = 10) was 0.02 μg g⁻¹, calculated for 0.2 mg of sample. The results obtained for six certified reference materials with concentrations between 0.40 and 11.6 ± 2.6 μg g⁻¹ Sb were in agreement with the certified values according to a Student's t-test for a 95% confidence level, using aqueous standards for calibration. The precision, expressed as relative standard deviation, ranged between 7% and 17% (n = 5).