Determination of Phenolic Acids and Quercetin in Brazilian Red Wines from Vale do Sao Francisco Region Using Liquid-Liquid Ultrasound-Assisted Extraction and HPLC-DAD-MS

This work describes a method for the determination of gallic, caffeic and p-coumaric acids, as well as quercetin, in Brazilian red wines by employing reverse phase high performance liquid chromatography (RP HPLC) coupled to diode array and mass detectors. The method was performed using a sample volume of 10 mu L. The limits of detections were 0.36, 0.27, 0.33 and 0.59 mg L-1 for gallic acid, caffeic acid, p-coumaric acid and quercetin, respectively. The precision, as estimated by the relative standard deviation, was between 1.0 and 2.0% for different concentrations of gallic acid, caffeic acid, p-coumaric acid and quercetin. The accuracy was evaluated by addition and recovery experiments, and the obtained values were between approximately 92 and 117% recovery. The method was then applied to the analysis of red wine samples that were collected from the Sao Francisco region, Bahia State, Brazil. The concentrations of analytes were determined in ten Brazilian wines and varied from 5.26 to 10.22 mg L-1 for quercetin, 6.65 to 43.92 mg L-1 for gallic acid, 3.58 to 7.83 mg L-1 for p-coumaric acid, and 3.59 to 10.5 mg L-1 for caffeic acid.