Potentiometric determination of salicylhydroxamic acid (urinary struvite stone inhibitor) based on the inhibition of urease activity

A novel, sensitive and selective enzymatic potentiometric method for the determination of SHAM drug (salicylhydroxamic acid) is described. It is based on the fast and potent inhibitory action of SHAM on urease-catalyzed urea hydrolysis. The initial rate of the urea/urease reaction is potentiometrically monitored using an ammonia gas sensor. Effects of urease activity, urea substrate concentration, incubation time, temperature and pH are demonstrated. Under optimized conditions, there is a linear relationship between the degree of enzyme inhibition and SHAM concentrations over the range 0.5–7 μg ml−1, with a 3σ detection limit of 0.1 μg ml−1. Determination of SHAM in some pharmaceutical preparations shows an average recovery of 98% of nominal and a mean relative standard deviation of 1%. Drug decomposition products and metabolites (salicylic acid and salicylamide) do not interfere.