MULTIVARIATE OPTIMIZATION OF SAMPLE PREPARATION PROCEDURE FOR MACRO AND MICROELEMENTS DETERMINATION IN GUARANA SAMPLES

Guarana is a typical fruit of the Amazon region and quite traditional in Brazil. The guarana seeds exhibit strong stimulating action due to high methylxanthines concentration (mainly caffeine) in its chemical composition. Furthermore, guarana is also a rich source of flavonoids such as catechin and epicatechin, characterize it as a species with potential antioxidant activity1. However, there are still few works related to the macro and microelements concentration in this fruit. Therefore, this work aimed to the use of multivariate optimization for sample preparation procedure and determination of K, Mg, Ca, P, S, Cu, Fe Mn and Zn in guarana seeds samples employing inductively coupled plasma optical emission spectrometry (ICP OES). Microwave-assisted digestion with diluted nitric acid was employed for sample preparation. For procedure optimization, was used a simplex centroide mixture design with the reagents HNO3, H2O2 and H2O and a heating program previously established. The developed method was validated considering analytical parameters such as limits of detection (LOD) and quantification (LOQ) and instrumental precision. Accuracy was evaluted through CRMs analysis of rice flour (NIST 1568b) and pine needles (NIST 1575a), where the found and certificated values did not present a significant difference. The chemometric strategies used in this work showed to be effective to optimization of guarana sample preparation and macro and microelements determination by ICP OES. The procedure will be subsequently applied for determination of K, Mg, Ca, P, S, Cu, Fe Mn and Zn in guarana seeds produced in different cities from south region of the Bahia State, Brazil.