Experimental design for the determination of polyphenols by liquid chromatography: application to the chemometric characterization and classification of beers

Abstract

This paper describes the development and application of a simple, rapid and inexpensive chromatographic method to determine polyphenols in beers. The separation was optimized by experimental design considering both resolution and analysis time as the objectives. Figures of merit were established under the selected experimental conditions. In general, repeatabilities of peak areas were better than 2%, detection limits were in the order of magnitude of 0.01 mg L⁻¹ and quantitative recovery percentages were about 100 ± 5. Differences in the polyphenolic composition among beer types were encountered to be relevant. This finding was exploited to perform the characterization of commercial beers using chemometric methods such as principal component analysis. The results indicated that coumaric and ferulic acids were more abundant in lager while syringic and gentisic acids were typical of some ale varieties. Concentrations of polyphenols in the samples were used to build classification models to discriminate among lager and ale classes. Models proved to be highly efficient in terms of sensitivity and specificity. It was found that all the samples were correctly assigned to their actual classes.