Repressing effects of sodium dodecyl sulfate on solvent-gelatinization of urine samples

The present work aimed to use a small volume of solvent for extraction of a large volume of urine sample in order to reduce the increase in hazardous waste. Sodium dodecyl sulfate (SDS) was found to exert an ability to repress gelatinization of solvent, which could be caused by shaking a small volume of solvent with a large volume of urine sample. Use of SDS provided the following simple method. Filtrate (100 ml) of a human urine sample (pH 9 - 10 or 3 - 4) was spiked with 100 μl of 5% SDS solution, and shaken with 2.5 ml of chloroform. The clear, separated chloroform layer was dried in a glass tube (2 ml), and the residue dissolved in solvent (chloroform: 50 μ1) and subjected to analysis. This characteristic behavior of SDS for separation of clear chloroform was interpreted by hypotheses deduced from chemical equilibria among SDS, protein, and chloroform.