Modifications to the azomethine-H method for determining boron in water

In the traditional azomethine-H methods, aqueous azomethine-H solutions readily hydrolyze at near neutral pH to form salicylaldehyde and the aminonaphthol, H-acid. Long color development times have been required, during which boron catalyzes the re-condensation of the hydrolysis products to the Schiff base. As a result of these findings, a new, rapid procedure has been developed based on the boron-catalyzed condensation of salicylaldehyde and H-acid. The conditions for formation and measurement of the Schiff base product have been optimized to provide excellent selectivity and sensitivity for the determination of soluble boron in water. A possible mechanism for the boron-promoted condensation reaction is suggested.