New phase separator for extraction-spectrophotometric determination of anionic surfactants with Malachite Green by flow injection analysis

A simple flow injection spectrophotometric method for the determination of anionic surfactants in river water was studied. A three-channel flow system was assembled. The distilled water as a carrier and 5 x 10(-5) mol l(-1) Malachite Green (MG) dissolved in 0.1 mol l(-1) CH3COONa-CH3COOH buffer solution (pH 5) were delivered at 1.94 ml min(-1). The mixed solvent (toluene + methylisobutyl ketone (MIBK) = 1 + 1) was pumped at 0.78 ml min(-1). Other conditions were the extraction coil 0.5 mm i.d. x 3 m, the reaction temperature 20 degrees C and the sample size 200 mu l. The calibration graph was linear in the range 0.1 - 0.4 ppm at 626 nm. The detection limit (S/N = 3) was 18 ppb and a sample frequency of 20 h(-1) was attained. The relative standard deviation (n = 7) for 0.4 ppm standard sodium dodecylsulfate (SDS) solutions was 1.1%. And also, new phase separator with a convenient connector was designed. This Fl method was applied to the determination of anionic surfactants in river water. (C) 1998 Elsevier Science B.V.