Chemometric Optimization of QuEChERS Extraction Method for Polyphenol Determination in Beers by Liquid Chromatography with Ultraviolet Detection

QuEChERS methodology is a new alternative for polyphenol analysis in foods and beverages. This extractive and clean up method includes several steps that should be optimized to accomplish a fast and efficient extraction. In this work, chemometrics tools were applied to optimize QuEChERS parameters for polyphenol extraction from beers. By means of D-optimal screening design, the most influential extraction parameters were defined, i.e., acetonitrile volume, acidity, PSA, and C-18 amount. These parameters were optimized applying a central composite design with desirability function, establishing the following optimal conditions: 2.5mL of acetonitrile as extraction volume, 0.5% v/v of formic acid for sample acidification, 40mg PSA for d-SPE step, and 175mg of C-18. Method validation was carried out according to International Conference on Harmonization recommendations. Data calibration curves (0.10-10.00mgL(-1)) fitted a linear regression model with determination coefficients (R-2) 0.992. Repeatability (relative standard deviation, RSD) and intermediate precision (RSD) showed values 4.81% (n=6) and 6.71% (n=3), respectively. Recovery (n=3) at three levels ranged from 93.98 to 119.92% (RDS 4.40%) and quantification limits ranged from 0.009to0.118gmL(-1). Applying the optimized and validated method, 10 beer samples were analyzed. The principal phenolic acids found were t-ferulic acid, caffeic acid, p-coumaric acid, and p-hydroxybenzoic acid. Individually, t-ferulic acid showed the highest concentration in all samples presenting a content ranged from 0.01 +/- 0.01 to 2.25 +/- 0.02gmL(-1). The proposed methodology proved to be fast, reliable, and efficient for the determination of polyphenols in beer.