Determination of Br, Cl and I in honey using ICP-based techniques following microwave-assisted wet digestion with alkaline H2O2 in a single reaction chamber

Abstract

In this work, a sample preparation method using only H₂O₂ in an alkaline medium in a single reaction chamber system (SRC-UltraWave™) was evaluated for honey digestion and for further determination of Br, Cl and I by inductively coupled plasma (ICP)-based techniques. Some important parameters, such as temperature, volume of H₂O₂, sample mass and volume of NH₄OH, were evaluated to produce digests with the minimum concentration of residual carbon (RC). Determination of RC and Cl was carried out using inductively coupled plasma optical emission spectrometry (ICP-OES), while Br and I were determined by inductively coupled plasma mass spectrometry (ICP-MS). Digestion was performed using up to 500 mg of honey, 8 mL of H₂O₂, 500 μL of NH₄OH and a maximum temperature and pressure of 270 °C and 199 bar, respectively. The digests obtained by the proposed method presented a concentration of RC lower than 220 mg L⁻¹ combined with an alkaline pH that minimized memory effects during ICP-based technique analysis. The accuracy of the proposed method was evaluated by analysis of certified reference materials NIST 8433 (corn bran) and NIST 1568a (rice flour), and by comparison between the results obtained using the proposed method and those obtained by microwave-induced combustion (MIC). Significant differences were not observed on comparing the results of the proposed method with reference values of CRMs and MIC. Limits of detection obtained by the proposed method were 10 μg g⁻¹ for Cl using ICP-OES and 0.03 and 0.005 μg g⁻¹ for Br and I (ICP-MS), respectively.