Abstract The surfactant presence in a sample may cause distortion of the flow injection peak obtained with amperometric detection at a mercury drop electrode. Distortion depends on detection parameters and flow system operating parameters and in some cases it may be eliminated by their careful optimization. Introduction of fumed silica into the carrier solution allows the dynamic removal of surfactant during the sample passage through the mixing coil. In the case of higher surfactant concentration in the sample, addition of fumed silica directly to the sample may be effective. Examples with amperometric detection as well as anodic stripping and adsorptive stripping voltammetric detection are described.