Method development for the determination of chromium and thallium in fertilizer samples using graphite furnace atomic absorption spectrometry and direct solid sample analysis

Abstract

A method has been developed for the determination of chromium and thallium in fertilizer samples using line source graphite furnace atomic absorption spectrometry (LS-GF AAS) with Zeeman-effect background correction and direct solid sample analysis. The results obtained with this equipment were compared with those obtained with high-resolution continuum source graphite furnace atomic absorption spectrometry (HR-CS GF AAS) to verify the absence of spectral interferences. For chromium, it was necessary to employ magnesium as a chemical modifier, and the optimum pyrolysis and atomization temperatures were 1600°C and 2500°C, respectively. For thallium, these temperatures were 900°C and 1700°C, and the determinations were made without a modifier. For chromium, the limit of detection (LoD) for LS-GF AAS and HR-CS GF AAS were 150ngg−1 and 60ngg−1, respectively. For thallium the LoD were 15ngg−1 for LS-GF AAS and 3ngg−1 using HR-CS GF AAS. The accuracy of the methods was verified using the certified reference materials NIST SRM 695 and NIST SRM 2704. The results obtained with the two spectrometers showed no significant difference at the 95% level of confidence. Using HR-CS GF AAS, it was possible to confirm the absence of spectral interferences in the determination of both elements in the investigated fertilizers.