POTENTIOMETRIC TITRATIONS OF SOME 0,0'-SUBSTITUTED ACID AZO DYES

Titrations based on both complex formation and ion-pair formation prin ciples have been used in assaying nine anionic azo dyes, namely C.I. 1 3900, C.I. 15685, C.I. 15705, C.I 15710, C.I. 16680, C.I. 18744, C.I. 18760, C.I. 18821 and Calmagite. The results show that the titrations of the dye anions can be performed using quaternary nitrogen salts as titrants, and can be monitored using a simple PVC membrane coated-wire electrode as a sensor in media buffered to an optimum pH value depend ing on the protolytic equilibria of the determinand. The complex forma tion titrations with copper(II) nitrate and copper(II) ion-selective e lectrode can also be carried out in either acetate or ammonia buffers. By comparing the results of both methods, more reliable conclusions c an be made with regard to the sample purity.