Characterization of sodium laureth sulfate by reversed-phase liquid chromatography with evaporative light scattering detection and 1H nuclear magnetic resonance spectroscopy

A direct and effective method utilizing reversed-phase liquid chromatography combined with evaporative light scattering detection was developed to determine the relative ratio of different alkyl chain lengths, to quantify the average ethylene oxide (EO) level and to identify EO distribution in the presence of sodium laureth sulfates. A C8 bonded silica gel column and an acetonitrile–water gradient mobile phase containing ammonium acetate were used as the best stationary and mobile phase, respectively. The results were confirmed by nuclear magnetic resonance spectroscopy. The detection limit was 80 μg/mL and the calibration curve, i.e., the log–log plots (peak area vs. concentration), was linear in the working range of 80–4200 μg/mL with R2 values of above 0.999 (in the case of 3 mol sodium laureth sulfates). Furthermore, the application of the chromatographic method to a commercial product without pretreatment was presented. The raw material was identified by fast atom bombardment mass spectrometry.