Sodium nitrate and tungsten as matrix modifiers for the determination of arsenic in shotgun pellets by electrothermal atomic absorption spectrometry

Abstract

A method for the determination of arsenic in a complicated sample matrix by Zeeman effect electrothermal atomic absorption spectrometry using tungsten and sodium nitrate as matrix modifiers was developed. The determination of arsenic in SRM C2416 (Bullet Lead) and SRM 2710 (Montana Soil) by ETAAS using a mixture of palladium and magnesium nitrate as a matrix modifier failed to obtain the certified concentrations at the 95% level of confidence using the t-test. Both tungsten and sodium nitrate as matrix modifiers stabilized arsenic so that the certified concentrations of the SRMs were determined with high accuracy and precision (RSD < 4%). The high values of the regression correlation coefficients (r > 0.999), with low detection and quantification limits, were obtained in the calibration range 20–100 µg L−1. Sample matrix interferences can be eliminated by increasing the pyrolysis temperature to 1400 °C with tungsten and to 1500 °C with sodium nitrate matrix modification. The standard additions method was also carried out in the case of SRM C2416 in order to check the linear relationship between integrated absorbance and concentration for the calibration range used. The new method was utilized for the analysis of shotgun pellets.