Antimony and chromium determination in Brazilian sugar cane spirit, cachaça, by electrothermal atomic absorption spectrometry using matrix matching calibration and ruthenium as permanent modifier

Abstract

This work reports a method for the determination of antimony and chromium in Brazilian sugar cane spirit, cachaca, by electrothermal atomic absorption spectrometry (ET-AAS) employing matrix matching calibration and ruthenium, thermally deposited (500 µg), as permanent modifier. The best pyrolysis and atomisation temperatures were 600 °C and 1400 °C for antimony while for chromium it was 700 °C and 2500 °C, respectively. For chromium, the peak returned to the baseline after 15 s in the absence of any modifier, whilst using Ru as permanent modifier, the peak returned to the baseline in 5 s, showing high symmetry. The characteristic mass (mo) obtained for chromium was 2.4 pg without modifier and 2.5 pg with Ru permanent (recommended 8.0 pg). For antimony it was 43.4 pg and 24.6 pg without modifier and with Ru permanent, respectively (recommended 200 pg). Matrix matching calibration curves (aqueous solutions 40% v/v in ethanol) gave a value of r (linear regression coefficient) higher than 0.999 for the two analytes. For antimony, two samples of cachaca spiked with 30.0, 60.0 and 90.0 µg l−1 showed a range of recovery from 98.8% to 110.0%, while for chromium it was from 101.7% to 107.9%. The detection limits (k = 3, n = 10) were 43 pg for antimony and 2 pg for chromium. The results obtained from analysis of fifty-two samples of cachaca, from Alto Vale do Jequitinhonha, Minas Gerais State, Brazil, varied from non-detectable to 39.1 µg l−1 for antimony and the RSDs, (n = 3), from 2.87% to 11.10%. For chromium, the same samples showed results from 0.64 to 1.53 µg l−1 (RSDs from 0.04% to 11.76%).