Evaluation of standard dilution analysis (SDA) of beverages and foodstuffs by ICP OES

Abstract

A procedure is described using the novel standard dilution analysis (SDA) calibration method for the determination of As, Cd, Cr, Cu, Fe, Mn, Pb, Se and Zn in drinks and foodstuffs by Synchronous Vertical Dual View (SVDV) ICP OES. SDA parameters such as standards concentrations, dilution ratio, signal plateau duration and internal standard element and concentrations were evaluated to improve accuracy, precision and sensitivity. Liquid sweetener, soy sauce, vinegar, grape juice, coconut water, red wine, cachaça (Brazilian sugarcane spirit), beer, energy drink, isotonic and soft drink were analyzed after a 10-fold dilution with 1% v/v HNO₃. Spiked samples were analyzed to check the method's accuracy. Recoveries were in the 89–111% range, with precisions better than 4.7%. Results were also compared with values obtained with the traditional calibration methods of external calibration, internal standardization and standard additions. Limits of detection for SDA were in the 3–20 μg L⁻¹ range, which are slightly higher than those obtained using external calibration (0.3–9 μg L⁻¹). Arsenic, Cd and Pb were not found in the samples evaluated. Concentrations determined for the other analytes were in the following ranges: 174 ± 23 μg L⁻¹ Cr, 843 ± 41 μg L⁻¹ Cu, 266–3903 μg L⁻¹ Fe, 1420–6700 μg L⁻¹ Mn, 300–1790 μg L⁻¹ Se, and 1030–14 520 μg L⁻¹ Zn. The SDA-ICP OES method is a simpler and faster alternative to perform matrix-matching with adequate accuracy and precision.