[Study on the mechanism of color changes of Azur A and sodium dodecyl sulphate before micelle formation].

The mechanism of color changes of sodium dodecyl sulphate(SDS) and Azur A (AA) before micelle formation was studied by spectral probe. The changes in the absorption spectra of SDS-AA and chondroitin sulfate(CS)-AA complexes were compared. The influence of ethanol and NaCl on the absorption spectra of SDS-AA complex was investigated. It was found that SDS-AA system showed color changes from blue to amaranth to blue due to the difference in the spatial orientation aggregative degree of AA binding on SDS regular aggregate. The critical concentration of premicelle formation (CPC) was found to be 1.0 x 10(-4) mol x L(-1) by the relation between c(SDS) and deltaA498/deltac(SDS).