Gel Filtration Study of the Effect of Urea on the Dissolution State of Sodium Dodecyl Sulfate

Using gel columns of Sephadex G 50 Fine and CPG gel, gel filtration studies were made of the sodium dodecyl sulfate (SDS)–urea system. The results demonstrated that both the CMC and the elution volume of SDS were increased by the addition of urea. The increase of the elution volume indicates the decrease in micellar size, and this coupled with the increase of CMC indicates the increased difficulty of micelle formation by the addition of urea. The direct interaction between SDS and urea was also examined by the gel filtration method and such interaction was confirmed to be absent both below and above the CMC of SDS. Furthermore, the micellar weight of SDS was estimated by the gel filtration method and values of 23000 and 11000 were obtained for SDS solutions containing 0 and 3 mol dm−1 urea, respectively.