SEPARATION AND DETECTION OF NON-CHROMOPHORIC, ANIONIC SURFACTANTS

The newly developed Solid Phase Reagent (SPR) permits the conductivity detection of various alkylsulfonates and alkylsufates. In its present version, SPR is an aqueous suspension of submicron particles of a polymeric cation exchange material in the hydrogen form. The SPR is pumped into the eluent stream coming from the separation column. The post-column reaction transforms the tetrabutylammonium alkyl sulfate or sulfonate into the corresponding free acid. This changes the analytes into more conductive species. At the same time the tetrabutylammonium borate eluent is converted to the low conducting boric acid. Both types of post-column reactions greatly increase the sensitivity of detection of conductivity. The conductivity detection method with the help of SPR also makes it possible to employ gradient elution for separations of complex mixtures of alkylsulfates or sulfonates. Such gradient separations are preferably carried out on silica based reversed-phase columns, rather than on polymeric based reversed-phase columns. The latter type of columns shows better tolerance to increased levels of the organic solvents as well as higher separation efficiency.