Colorimetric method for the analysis of residual anionic or cationic surfactants

Claim 1

A method for the analysis of residual anionic and cationic surfactants present in an aqueous solution including the steps of: obtaining a known volume first sample of the aqueous solution to be tested; adding buffer solution, a first dye reagent and chloroform to the first sample and mixing thoroughly to permit the formation of a water-chloroform two-phase mixture; allowing the first sample to stand undisturbed to permit the separation of chloroform from the two-phase mixture, the separated chloroform layer being colored in the presence of residual anionic surfactants in the first sample; if the separated chloroform layer is colored, colorimetrically determining the concentration of the residual anionic surfactants which are directly related to the intensity of the color of the chloroform layer; and if the chloroform layer of the two-phase mixture of the first sample is not colored the first sample contains no residual anionic surfactants and the following further steps are carried out: a. obtaining a known volume second sample of the aqueous solution to be tested; b. adding buffer solution, a second dye reagent and chloroform to the second sample and mixing thoroughly to permit the formation of a water-chloroform two-phase mixture; c. allowing the second sample to stand undisturbed to permit the separation of chloroform from the two-phase mixture, the separated chloroform layer of the second sample being colored in the presence of residual cationic surfactants in the second sample; and d. if the separated chloroform layer of the second sample is colored, colorimetrically determining the concentration of the residual cationic surfactants which are directly related to the intensity of the color of the chloroform layer of the second sample, if the chloroform layer of two-phase mixture of the second sample is not colored the second sample contains no residual ionic surfactants.

Claim 2

A method for the analysis of residual anionic and cationic surfactants present in an aqueous solution including the steps of: obtaining a known volume first sample of the aqueous solution to be tested; adding buffer solution, a first dye reagent and chloroform to the first sample and mixing thoroughly to permit the formation of a water-chloroform two-phase mixture; allowing the first sample to stand undisturbed to permit the separation of chloroform from the two-phase mixture, the separated chloroform layer being colored in the presence of residual anionic surfactants in the first sample; if the separated chloroform layer is colored, colorimetrically determining the concentration of the residual anionic surfactants which are directly related to the intensity of the color of the chloroform layer; and if the chloroform layer of the two-phase mixture of the first sample is not colored the first sample contains no residual anionic surfactants and the following further steps are carried out: a. obtaining a known volume second sample of the aqueous solution to be tested; b. adding buffer solution, a second dye reagent and chloroform to the second sample and mixing thoroughly to permit the formation of a water-chloroform two-phase mixture; c. allowing the second sample to stand undisturbed to permit the separation of chloroform from the two-phase mixture, the separated chloroform layer of the second sample being colored in the presence of residual cationic surfactants in the second sample; and d. if the separated chloroform layer of the second sample is colored, colorimetrically determining the concentration of the residual cationic surfactants which are directly related to the intensity of the color of the chloroform layer of the second sample, if the chloroform layer of two-phase mixture of the second sample is not colored the second sample contains no residual ionic surfactants.