Diazolidinyl urea, imidazolidinyl urea และ Quaternium-15 were eluted from the column between 15 and 22 minutes with a gradient from 93 to 60 % acetonitrile. Other constituents of the creams’ formulations were eluted in the beginning of the chromatogram. An equilibrating step was necessary before the next injection to reach a stable baseline at the start of analysis.
For determining lower concentrations of Quaternium-15, this method needs to be improved. Its limit of detection is currently 0.2 mg/ml, which corresponds to the maximum allowed concentration in skin-care products (0.2%).