A Study on the Determination of Trace Cetyltrimethylammonium on the Basis of the Discolor Reaction of Brilliant Green

Because of the function of the quaternary ammonium cationic surfactant of cetyltrimethylammonium bromide (CTMAB) or cetylpyridinium bromide (CPB) at pH 7.00 Tirs HCl buffer solution, Brilliant Green produced a sensitive discolor reaction. Furthermore, it was found that the discolor degree of Brilliant Green had the quantitative relationship with micro amount CTMAB or CPB. In this paper, the discolor reaction conditions for Brilliant Green CTMAB system has been studied, and the discolor reaction mechanism has been discussed. Also, the methods for the determination of micro amount CTMAB and CPB have been developed using the discolor reaction. It was found that the method had high sensitivity for the determination of CTMAB or CPB ( e CTMAB =1.62×10 4 L·mol -1 ·cm -1 , e CPB =1.13×10 4 L·mol -1 ·cm -1 ). Beer's law was obeyed in the range of 0~6.0×10 -5 mol/L CTMAB and 0~8.0×10 -5 mol/L CPB, respectively. The method has been applied satisfactorily to the determination of micro amount CTMAB in electrodeposit waste water.