Development of a Simple and Fast Procedure Based on Acid Dilution for Determination of Macro and Microelements in Guarana-Based Beverages by ICP OES

Abstract

A simple analytical procedure is proposed for the direct analysis of guarana-based beverages in order to determine nutrient elements by inductively coupled plasma optical emission spectrometry (ICP OES). A Box-Behnken design, combined with Derringer’s desirability function, was applied to the simultaneous optimization of the ICP OES radiofrequency (RF), sample volume and nitric acid concentration. Using this approach, optimal conditions were established as RF power of 1.40 kW, and 5.0 mL of sample diluted twice with 0.5 mol L-1 HNO3. The optimized procedure allowed the determination of Cu, Fe, Mn, Zn, K, Ca, S, P and Mg with limits of quantification of 10.0, 2.0, 0.6, 6.0, 66.0, 65.0, 235, 40.0 and 20.0 μg L-1, respectively. Accuracy of the method was evaluated through analysis of water standard reference material (SRM NIST 1643f) and by additionrecovery experiments, in which satisfactory recoveries were obtained. The procedure was applied for the analysis of guarana-based soft and energy drinks. The concentration ranges (mg L-1) were: 0.36‑43.3 (Ca), 4.04-192 (K), 0.36-44.8 (Mg), 10.1-1,073 (S), 0.04-92.4 (P), < 0.010-0.0174 (Cu), < 0.002-0.294 (Fe), < 0.006-0.06 (Zn) and < 0.0006-0.168 (Mn).