Bromide determination in pharmaceutical preparations using indirect gas-diffusion flow injection method with amperometric detector

The indirect gas-diffusion flow injection method (FI) was modified, optimized and successfully applied to bromide determination in various samples such as active substances, drugs, organic substances and water samples. The method is based on the oxidation of bromide to bromine in acidic medium, which diffuses through PTFE membrane into the acceptor flow that carried bromine to the amperometric cell. The flow amperometric detection was carried out at the potential of +0.65 V (vs Ag/AgCl) when injected sample volume was 100^L. Results obtained by FIA were confirmed by cyclic voltammetry (CV). The linear calibration graph was obtained over the concentration range 0.1-10x10-3 mol/L and 2.5-100x10-6 mol/L bromide solutions. Relative standard deviation was 1.23% for 5x10-6 mol/L bromide solution and 0.11% for 0.25x10-3 mol/L bromide solution (n=6, for both cases). The limit of detection was 5x10-8 mol/L. The described method requires small quantities of samples and prior extraction of the analytes is not necessary. The method enables 60 analyses per hour.