Electrochemical paper-based analytical devices containing magnetite nanoparticles for the determination of vitamins B2 and B6

• ePADs comprising graphite, automotive varnish and magnetite nanoparticles are proposed. • Magnetite nanoparticles improve the ePAD sensitivity. • Disposable devices allow the use of small amounts of sample. • ePADs serve for the determination of organics like vitamins B 2 and B 6 . Disposable electrochemical paper-based analytical devices were developed from a conductive ink using graphite powder, automotive varnish and magnetite nanoparticles. The addition of magnetite nanoparticles in the conductive ink improved the sensitivity of the analytical devices. The devices were applied in the quantification of vitamins B 2 (VB 2 ) and B 6 (VB 6 ) in commercial dietary supplements. The characterization of the analytical devices was carried out by microscopy and electrochemical techniques. Square wave voltammetry (SWV) was used to study the electrochemical behavior of the vitamins and the experimental parameters were optimized (pH, supporting electrolyte and SWV parameters). The calibration plot for VB 2 (−484 mV vs . graphite) was obtained in Britton-Robinson buffer (pH 2.0) in the range of 2.0 to 20.0 μmol L −1 with a detection limit of 0.25 µmol L −1 . Similarly, for the VB 6 (+675 mV vs . graphite), the calibration plot was obtained in McIlvaine buffer (pH 4.0) in the range of 0.2 to 2.0 mmol L −1 with a detection limit of 29.5 µmol L −1 . The analytical devices were employed to determine VB 2 and VB 6 levels in B-complex supplements (capsules and sublingual liquid) and the results were compared with those provided by fluorescence spectrometry. The statistical analysis showed no considerable difference in terms of the precision and accuracy of the data obtained by both methods.