Junhui Zou, S. Motomizu, M. Oshima
Oct 1, 1992
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0
Influential Citations
4
Citations
Journal
Analytical Sciences
Abstract
Since boric acid has poor reactivity in an aqueous solution, it is generally difficult to find a useful complexing agent. The most common spectrophotometry uses Curcumin' and Methylene Blue2 methods. The former is sensitive but requires evaporation to dryness. The latter method, developed by Ducret2, requires extraction of the ion associate formed between tetrafluoroborate anion and Methylene Blue into 1,2dichloroethane. Since these procedures are both troublesome and time-consuming, a rapid, simple, flow injection method (FIA) using Azomethine H has been reported.3 Azomethine H, however, is an unstable reagent in aqueous solutions and its sensitivity for boron determination is not very high. H-resorcinol,l-(2,4-dihydroxyphenylazo)-8-hydroxynaphthalene-3,6-disulfonic acid (disodium salt), reacts with boric acid in an weakly acidic solution to form a 1:1 molar ratio complex;4 its reactivity and sensitivity were the best of the examined ten analogues.5 The authors recently reported highly sensitive HPLC using an anion exchanger column and a spectrophotometric detector, in which separation of the boron-H-resorcinol complex from excess reagent, itself, was accomplished using an eluent containing sodium perchlorate.6 Complex formation, however, requires a long time at room temperature and, therefore, acceleration of the reaction by heating the solution was required before sample injection. In this study, a simple, rapid and sensitive HPLC for the determination of boric acid coupled with on-line complex formation was developed.