Automated flow-injection pseudotitration of boric acid

An automated flow-injection pseudotitrimetric determination of boric acid, using a flow-injection photometric analyzer controlled by a microcomputer, is described. The method is based on the injection of 200 microL of sample in a flowing stream of mannitol-bromothymol blue "titrant" and measuring the peak width in time units. Equivalent times of 10-70 s are measured with CV values of 0.1-0.4% (n = 5) and the analytical range is 1.5-309 mg/100 mL (2.5 X 10(-4)-5 X 10(-2 M) of boric acid. The method was evaluated by performing recovery studies in mixtures (mean 99.8%) and assays of commercial preparations which were compared with the official classical titrimetric method.