Anionic surfactant detection

Abstract

Disclosed herein are methods for the detection and/or quantification of anionic surfactants. Also disclosed herein are test kits, which utilize the disclosed methods, to estimate the anionic surfactant concentration in samples, such as environmentally-derived samples. In some specific embodiments, the method and the test kit may be used to detect, among other things, aqueous film forming foams that comprise anionic surfactants.

1 . A method for detecting and/or quantifying an anionic surfactant in a sample, the method comprising: providing a cationic dye, wherein the cationic dye is capable of complexing with an anionic surfactant from the sample to form a detectable dye-surfactant complex that is preferentially soluble in a solvent which is substantially immiscible with the sample; providing a solvent which is substantially immiscible with the sample; contacting the cationic dye with either the sample and the solvent or an extract of the sample in the solvent such that an anionic surfactant in the sample or extract complexes with the cationic dye to form a detectable dye-surfactant complex that is preferentially soluble in the solvent; detecting and/or quantifying the dye-surfactant complex in the solvent, wherein the presence of the dye-surfactant complex in the solvent indicates the presence of an anionic surfactant in the sample. 
     
     
         2 . A method according to  claim 1  wherein the cationic dye comprises ethyl violet or a derivative thereof. 
     
     
         3 . The method of  claim 1  wherein the solvent comprises ethyl acetate. 
     
     
         4 . The method of  claim 1  wherein the cationic dye comprises ethyl violet or a derivative thereof and the solvent comprises ethyl acetate. 
     
     
         5 . The method of  claim 1  wherein the sample comprises a water sample. 
     
     
         6 . The method of  claim 1  wherein the sample comprises a soil sample. 
     
     
         7 . The method of  claim 1  wherein the method further comprises a concentration step to increase the concentration of one or more anionic surfactants in the sample prior to contacting the sample with the cationic dye and/or solvent. 
     
     
         8 . The method of  claim 7  wherein the concentration step comprises solid phase extraction. 
     
     
         9 . The method of  claim 1  wherein the dye-surfactant complex is detected and/or quantified in the solvent using an optical detection method. 
     
     
         10 . The method of  claim 9 , wherein the optical detection method comprises visual inspection of the solvent. 
     
     
         11 . The method of  claim 10 , wherein the visual inspection comprises comparison of the colour of the solvent with one or more visual reference colours. 
     
     
         12 . The method of  claim 9 , wherein optical detection method comprises spectrophotometry. 
     
     
         13 . The method of  claim 1  wherein the anionic surfactant comprises an anionic surfactant constituent of an aqueous film forming foam. 
     
     
         14 . The method of  claim 1  wherein the anionic surfactant comprises a fluorinated anionic surfactant. 
     
     
         15 . A kit for detecting and/or quantifying an anionic surfactant in a sample, the kit comprising: a cationic dye, wherein the cationic dye is capable of complexing with an anionic surfactant from the sample to form a detectable dye-surfactant complex that is preferentially soluble in a solvent which is substantially immiscible with the sample; and instructions for performing the method of  claim 1 . 
     
     
         16 . The kit of  claim 15  wherein the cationic dye comprises ethyl violet or a derivative thereof. 
     
     
         17 . The kit of  claim 15  wherein the kit further comprises a solvent which is substantially immiscible with the sample. 
     
     
         18 . The kit of  claim 17  wherein the solvent comprises ethyl acetate. 
     
     
         19 . The kit of  claim 15  wherein the kit further comprises a reaction vessel for contacting the sample with the cationic dye and/or solvent. 
     
     
         20 . The kit of  claim 15  wherein the kit further comprises one or more reference objects, each comprising one or more reference colours, for detecting and/or quantifying the dye-surfactant complex in the solvent.