Automated high-performance purification of surfactant solutions: study of convective-enhanced adsorption.

Due to the amphiphilic nature of surfactants, they generally contain traces of their more surface-active parent components irrespective of the as received surfactant's label declaration. These trace impurities are preferentially enriched in the surfactant's adsorbed layer. To attain the state of "surface chemical purity" that implies the absence of impurities in the adsorbed layer, we had developed an automatic high-performance purification apparatus years ago. Here we put forward an improved version of this successful technique that considerably reduces the time required to purify surfactant solutions by accelerating the adsorption through convection. The advantages and reliability of the new technique are demonstrated by the purification characteristics of different solutions of as-received surfactants of varying degree of purity. As the overall time gained with convective purification is of 1 order of magnitude, the improved technique is particularly favorable for surfactant solutions that are prone to hydrolysis or degradation.