Multivariate approaches applied to optimization of an ultrasound-assisted extraction procedure for determination of essential elements in guarana samples by ICP OES

Abstract

In the present work, a simple and high-throughput analytical procedure based on ultrasound-assisted extraction with diluted acid was proposed for the determination of Ca, Mg, K, P, S, Fe, Cu and Mn in guarana samples using inductively coupled plasma optical emission spectrometry. Two multivariate approaches were employed for optimization of the extraction procedure: mixture and Doehlert designs. The best experimental conditions were established by application of a multi-response function (overall desirability). An extractor medium composed of diluted nitric acid was selected for analytes extraction. Optimized conditions for ultrasound-assisted extraction followed the temperature of 60 °C, sonication time of 10 min and power of 100% applied to the ultrasonic bath. After the analytical validation step, the proposed procedure was successfully employed for determination of essential elements in thirty-three guarana samples from the state of Bahia, Brazil. Mass fractions higher than 0.42% (m m^-1) were found for potassium in all analyzed samples. For the other macro-elements, the mass fraction ranged from 514 mg kg^-1 (magnesium) to 0.19% m m^-1 (calcium). The mass fraction of micro-elements ranged from 5.1 to 91.3 mg kg^-1 for cooper and iron, respectively.

Keywords:
ultrasonic energy; multi-element extraction; chemometric tools; guarana seeds; ICP OES