A simple approach for amperometric determination of pyridoxine and caffeine in pre-workout supplements using batch injection analysis with boron-doped diamond electrode

This work reports an analytical strategy for the quantification of pyridoxine (PYR) and caffeine (CAF) in pre-workout formulations, specifically multi-ingredient performance supplements (MIPS) and encapsulated guarana powder (GP). The approach relies on batch injection analysis with amperometric detection (BIA-AD) employing a boron-doped diamond electrode (BDDE) as the working electrode. A straightforward correction factor (CF) was applied to enable caffeine determination at + 1.5 V in the presence of pyridoxine. The method provided low limits of quantification, 9.64 µmol L −1 for pyridoxine and 6.82 µmol L −1 for caffeine. Accuracy was assessed through spiking and recovery assays, yielding values between 90 % and 110 %, and the results showed good agreement with those obtained by the reference High-Performance Liquid Chromatography with Diode-Array Detection technique. Application of the method to real samples demonstrated that both analytes were successfully measured in multi-ingredient performance supplements. For guarana powder samples, the caffeine concentrations were consistent with the labeled values. Overall, the method offers a rapid, low-cost, portable, and environmentally sustainable alternative for the determination of pyridoxine and caffeine in pre-workout supplements. • First sequential analysis of PYR and CAF in pre-workout samples. • Development of a method with an inexpensive approach using the BIA-AD system. • Current responses of PYR and CAF are separated with a simple correction factor. • Methodology with low environmental impact, as confirmed by the AGREE tool.