Determination of Cl, Br, and I by ICP-MS using diluted acid: an environmentally friendly strategy for food analysis

A simple and environmentally friendly sample preparation protocol was developed for Cl, Br, and I determination by inductively coupled plasma mass spectrometry (ICP-MS). The proposed approach employs microwave-assisted digestion using diluted HNO₃ and auxiliary reagents, combined with simultaneous cooling, to improve the digestion efficiency and to ensure analyte retention and minimal losses by volatilization. The method was evaluated for food matrices comprising animal-derived products (whole milk powder, bovine liver, and bovine kidney) and plant-based seasonings (melissa tea, black pepper, and oregano). Conditions such as sample mass (from 100 to 600 mg), O₂ pressure (from 2.5 to 10 bar), H₂O₂ presence (3 mL of 30% solution), and HNO₃ concentration (from 0.5 to 14.4 mol L^-1) were evaluated. Optimal conditions were achieved using 2 mol L^-1 HNO₃ with either 7.5 bar O₂ or 3 mL of 30% H₂O₂. The methods provided low residual carbon content (6 - 11%) and suitable residual acidity, ensuring efficient digestion. Good agreement of the results was observed when compared to microwave-induced combustion (MIC), particularly for the method using O₂. Accuracy was assessed by using certified reference materials (CRM) of Whole Milk Powder (NIST 8435) and Peach Leaves (NIST 1547). The use of diluted acid significantly reduces reagent consumption and waste generation, rendering the proposed methods a green and effective alternative for halogen determination in animal-derived products and plant-based seasonings.