Study on the color reaction of 1-(2,6-dichloro-4-nitrophenyl) -3-(4-nitrophenyl)-triazene with cationic surfactant

The color reaction of 1(2,6dichloro4nitrophenyl)3(4nitrophenyl)Triazene(DCNPNPT)with cethyltrimethylammonium bromide(CTMAB) and cetylpyridinium bromide(CPB)were studied.In NaOH medium,DCNPNPT reacts with quartenary ammonium cationic surfactant(CTMAB,CPB)to form a purplered complex with the molar ratio of 1∶3.The molar absorptivities of CTMAB and CPB are 393×104L·mol1·cm1 and 416×104L·mol1·cm1 by using dualwavelength spectrophotometry.Beers law is obeyed in the range of 0～328×105mol·L1 for CTMAB,0～316×105 mol·L1 for CPB.The critical micella concentration of CTMAB and CPB in the color system was determined.The method was applied to the direct determination of cationic surfactant in water with satisfactory results.