Simultaneous Determination of Caffeine and Water-Soluble Vitamins in Energy Drinks by HPLC with Photodiode Array and Fluorescence Detection

The high-performance liquid chromatography (HPLC) method with photodiode array (PDA) and fluorescence (FL) detection for the simultaneous separation and determination of caffeine and water-soluble vitamins is described. The method is relatively rapid: 13 compounds can be analyzed within 30 min: caffeine; ascorbic acid (vitamin C); thiamine (vitamin B-1); riboflavin 5-phosphate (FMN, flavin mononucleotide) and riboflavin (vitamin B-2); nicotinic acid and nicotinamide (vitamin B-3); pantothenic acid (vitamin B-5); pyridoxal, pyridoxamine, and pyridoxine (vitamin B-6); folic acid (vitamin B-9); and cyanocobalamin (vitamin B-12). This HPLC method is designated for quantification of caffeine and water-soluble vitamins in liquid and tablet energy drinks as well as for determination of vitamins in vitamin supplements. The method was validated in terms of linearity, limit of detection (LOD) and quantification (LOQ), accuracy, and instrument precision. The LODs determined using HPLC-PDA ranged from 13 to 121 ng mL(-1) and using HPLC-FL were between 8 and 61 ng mL(-1). Intra- and interday instrument precisions for liquid energy drink, expressed as relative standard deviation (RSD), were less than 1.87 and 1.73 %, respectively, and less than 1.44 and 1.83 %, respectively, for tablet energy drink. The method could be useful in the quantitative analysis of caffeine and of water-soluble vitamins in energy drinks and vitamin supplements.