Coulometric Titrimetric Determination of Benzalkonium Bromide in Xin Jie Er Mie Liquid

Coulometric titrimetry was applied to the determination of benzalkonium bromide (BKB) in Xin Jie Er Mie liquid. A mixed solution of 0.09 mol·L-1 HNO3 solution and (w) 0.5% gelatin solution (10+1) was used as electrolytic solution, and silver rod was used as anode. A portion (5.00 mL) of the drug sample was added to the electrolyte and electrolyzed at a constant current of 10 mA. During electrolysis, precipitate of AgBr was formed between Ag+ liberated at the anode and Br- dissociated from BKB. When all the Br- was reacted and precipitated by Ag+, an abrupt increase of current occured denoting the end of titration. Content of BKB was calculated by the Faraday′s Law. Linear relationship between values of mass concentration of BKB and respective quantities of current consumed was kept in the range of 0.422 8-1.480 g·L-1 of BKB. In analysis of a same sample of the drug by this method and by the sodium tetraphenylboron titrimetry, consistent results were obtained by the 2 methods. Values of RSD (n=6) found for the coulometric titrimetric method was 0.9%. Values of recovery found by standard addition method were ranged from 99.6% to 102%.