Determination of boron by flow injection analysis using a conductivity detector

A now injection method for the determination of boron using a conductivity detector has been described. Boric acid injected into the flow system react s with mannitol (0.3 M) in the mobile phase and an equivalent amount of His liberated in the stream. The increase in the conductance of the mobile p hase due to the liberated H+ has been equated to the boron concentration in the sample. A linear calibration for light- and heavy-water samples contai ning 0-20 mu g/mL boron was obtained. Boron concentrations in the samples o f light and heavy water and lithium pentaborate solution have been measured . The interferences due to various ions such as Na+, Li+, Cu2+, Ni2+, Co2+, Fe3+, Al3+ SO42-, NO3-, F-, and Cl- could be eliminated by adopting a two- step sample pretreatment procedure. In the first step, all the anions were converted to Cl- by treating the sample solution with a strong anion-exchan ge resin. In the second step, the solution obtained from the first step was passed through a silver-guard cartridge to remove interfering cations and Cl-. The relative standard deviation was +/-0.25% for the determination of 1 mu g of boron in light water, and the limit of detection was 0.01 mu g pr esent in an injection volume of 100 mu L. The corresponding values for heav y water were +/-0.38% and 0.1 mu g, respectively.