Indirect determination of tetrahydroborate (BH−4) by gas-diffusion flow injection analysis with amperometric detection

Abstract A rapid, indirect gas-diffusion flow injection analysis (FIA) method with amperometric detection has been developed for the selective and sensitive determination of tetrahydroborate (BH − 4 ). The injected analyte reduces arsenic(III) to arsine. The arsine formed diffuses through the PTFE (polytetrafluoroethylene) membrane and is quantified amperometrically at a platinum working electrode. The precision of the technique was better than a relative standard deviation of 2.1% at 60 μ M levels and better than 0.5% at 0.1 m M , with a throughput of 60 samples/hr. The detection limit of the method was found to be 1 μ M (1.5 ng BH − 4 ) with a linear range up to 1 m M . The dynamic range extends over five orders of magnitude in BH − 4 concentration. The effects of working potential, concentration of As(III) and HCl in the reagent stream, type and flow rate of the acceptor solution, temperature and interferents on the FIA signals were studied.