The use of Ca + Pd + Zr as modifiers in the determination of sulfur by HR-CS GF MAS with solid sampling

Abstract

This paper proposes a universal combination of chemical modifiers for sulfur determination through carbon monosulfide (CS) monitoring by high-resolution-continuum source graphite furnace molecular absorption spectrometry and solid sampling analysis. Three certified reference materials containing sulfur (NIST 8414, 8415 and 1648a) and a variety of samples were submitted to the proposed method. The CS molecule was monitored at 258.056 nm using a platform coated with Zr and a combination of 10 μL Ca (1 g L⁻¹) and 4 μL Pd (10 g L⁻¹) placed over the sample. The best pyrolysis and vaporization temperatures were 400 °C and 2300 °C, respectively. Aqueous standard solutions were employed to obtain the calibration curve, using a mix of three sulfur compounds (ammonium sulfate, L-cysteine, and thiourea), and the linear range was from 0.033 μg to 4 μg S. The LOQ and the characteristic mass were 0.033 μg S and 0.011 μg S, respectively, while the accuracy was evaluated using different organic and inorganic reference materials, and good agreement (higher than 93%) with the certified values for S was observed.