Gel Filtration of Aqueous Sodium Dodecyl Sulfate

The tail analysis of gel filtration was applied to a sodium dodecyl sulfate (SDS) solution using Sephadex G-50. This method is more simple and useful than the frontal analysis method formerly reported. The relative elution rate of SDS micelle, Rm, increased with an increase in the SDS concentration above CMC, reached a maximum near 16 mmol/l and then decreased up to 100 mmol/l. The application of the Laurent-Killander equation gave a micellar radius of 17.6 Å at CMC and 11.7 Å at the maximum Rm, corresponding to aggregation numbers of 35 and 80, respectively. The apparent decrease of Rm observed above 20 mmol/l was due to an structural change of the Sephadex gel caused by the addition of SDS. The micellar weight was estimated referring to a substance of known molecular weight; it was found to be constant in the region from 15 to 100 mmol/l SDS. The results of gel filtration of the SDS solution using CPG-10 as a gel column were similar to the case of Sephadex G-50; a micellar weight and an aggregation number of 25000 and 88, respectively, in the constant Rm range were obtained.