A sensitive and stable IO 4 - -H 2 O 2 chemiluminescence (CL) system for flow injection determination of sodium dodecylbenzene sulfonate (SDBS) is described. Weak CL is emitted when H 2 O 2 is oxidized by sodium periodate. In this system, various surfactants enhance CL intensity, especially SDBS. The effects of non-polar organic solvents on CL are also reported. The 3σ detection limit for SDBS is 3.2x10 - 8 gml - 1 in a system using a trace of cyclohexane and the relative standard deviation of this method is 1.6% at 1.0x10 - 6 gml - 1 for 11 determinations; SDBS in detergents is determined.