ION-CHROMATOGRAPHIC DETERMINATION OF BORATE IN AQUEOUS SAMPLES TOGETHER WITH OTHER COMMON ANIONS

The conversion of boric acid (pK(a) approximate to 9) in a more acidic complex, using mannitol or sorbitol as ligands, has been exploited to obtain a sensitive and accurate method for the determination of boric acid by ion chromatography. Both separation and detection conditions have been selected on the basis of available thermodynamic data on the relevant equilibria, and then experimentally optimised on a conventio nal ion cromatograph equipped with a suppressed conductivity detector. The performances of the method are practically identical for the two eluent solutions adopted, containing mannitol or sorbitol: the detecti on limit is about 1 mu mol dm(-3), the linear response range extends u p to 200 mu mol dm(-3), the repeatability is better than 5% and the an alysis time is less than 6 min. Moreover, other common anions (i.e., a cetate, fluoride, and chloride) can be determined together with berate . The comparison of results with those obtained by conventional analyt ical techniques applied to real samples at known concentration of bera te allows the estimation of a negligible bias for the ion chromatograp hic method.