Spectrophotometric Determination of Cetylpyridinium Chloride with Bibromocarbaxylbenzenediazoaminoazobenzene

A novel spectrophotometric method for the determination of cetylpyridinium chloride(CPC)with dibromocarbaxylbenzenediazoaminoazobenzene is developed. In the medium of 1.0 mol/L sodiumhydroxide,CPC reacts with dibromocarbaxylbenzenediazoaminoazobenzene to form violet red 1∶2 complex of ion association in the presence of TritonX-100.This complex of ion association exhibits an absorption maximum at 580 nm with an apparent molar absorptivity of 3.7×10~4 L·mol~(-1_·cm~(-1_. Beer's law is obeyed of CPC in the concentration rang of 0~80 μg per 25 ml of solution. The proposed method based on the above colour reaction is simple and rapid, and toxic organic solvents are not used. It has been applied to the determination of trace CPC in tap water with satisfactory result.