Comparative study of two spectrophotometric reagents for catechol analysis in guarana seeds powder

In this article are described and compared two spectrophotometric methods for the analysis of catechol (o-hydroxyphenol) in Paullinea cupana var. sorbilis, popularly known as guarana. The pounded seed samples were extracted with ethanol 97% v/v and the solutions were treated with p-aminophenol in alkaline ethanolic medium or m-aminophenol and sodium metaperiodate in buffered aqueous solution (pH 3.0). The absorbance was measured at 586 nm and 520 nm respectively. Four different commercial products were analyzed and the results were compared with those obtained with the m-aminophenol method. Despite the good quality of the calibration curves, in the two methods the interference of the matrix was observed. This problem was settled using the standard addition method. Comparison between the results obtained by the two methods, using the statistical Student's t-test, showed that there is no significant difference at the 95% confidence level.14112913