Test methods for determining cationic and anionic surfactants in disinfecting and technological solutions

The purpose of the work was to develop Express methods for determining cationic and anionic surfactants in disinfectants and process solutions. The surfactant concentration was determined visually and colorimetrically by the intensity of color of the indicator zones of paper test strips or by the length of the colored (discolored) zones of test strips laminated in a polymer film. Semi-quantitative determination of surfactants in solutions was carried out by the intensity of color of the zones of indicator test strips pasted on the substrate (test titration on paper). Bromphenol blue was used as an indicator. The titrant was sodium dodecyl sulfate for cationic surfactants and cetylpyridinium chloride for anionic surfactants. Test strips were used for the determination of surfactants in the disinfectant solutions. The concentration in the range of 0.1 – 1.2% was determined by comparing the color with the standard color scale. The duration of the analysis was 3 – 5 min. Quantitative determination of surfactants was carried out by the length of the colored (discolored) zones of test strips glued in a polymer film. As an indicator for cationic surfactants, bromphenol blue (blue zone on the test strip) was used, and for anionic surfactants, an associate of bromphenol blue with cetylpyridinium chloride (discolored zone on the test strip). The determination range of the surfactant made up 16 – 1000 mg/liter. The concentration was determined according to a calibration graph representing the dependence of the length of the blue/discolored zone of the test strips on the concentration of surfactants in the solution. The relative standard deviation of the analysis results does not exceed 0.3; the analysis duration was 20 – 30 min.