Microwave-induced combustion for further determination of potentially toxic elements in honey by ICP-MS

Abstract

Microwave-induced combustion (MIC) was proposed in this study for honey decomposition aiming for As, Cd, Hg, and Pb determination by inductively coupled plasma mass spectrometry (ICP-MS). Sample mass (up to 1.0 g), absorbing solution (0.5 to 14.4 mol L^-1 HNO₃, and H₂O), heating program, and combustion aids were evaluated. The Eurachem guidelines were used for method validation. The proposed method enabled combustion of a high sample mass (0.8 g of honey, with 0.4 g of microcrystalline cellulose and 100 µL of 6 mol L^-1 NH₄NO₃) using 6 mL of an absorbing solution consisting of 1 mol L^-1 HNO₃, which resulted in low residual carbon in solution (< 25 mg L^-1). Honey samples from different geographical origins were analyzed. Results showed no significant difference in comparison to other two microwave decomposition methods, based on microwave-assisted wet digestion with single reaction chamber (MAWD-SRC) and microwave-assisted wet digestion (MAWD). Standard addition experiments resulted in recoveries higher than 98%. The limits of detection ranged from 1.10 (As) to 4.60 ng g^-1 (Pb). In addition to using only diluted reagents and resulting in digests virtually free of interferences, the proposed method was faster (< 30 min) than most of those presented in the literature.

Keywords: Honey analysis; ICP-MS; Inorganic contaminants in honey; Microwave-induced combustion; Sample preparation; Toxic element determination.