Reproducibility of retention time and peak area in comprehensive two-dimensional liquid chromatography

Comprehensive two-dimensional liquid chromatography is used to separate anionic, nonionic, and amphoteric surfactants by substance class, alkyl chain distribution, and degree of ethoxylation. A nearly orthogonal system with a hydrophilic interaction chromatography (HILIC) phase in the first and a reversed-phase material in the second dimension is applied to generate a separation with maximum peak capacity. The potential of the developed method is demonstrated by the reproducibility of retention time and peak area, which shows standard deviations less than 5 % and the analysis of real samples. An external calibration and the standard addition method were applied to determine unknown concentrations for the alkyl chain homologues of a betaine and for one ethoxylate (EO) homologue of a fatty alcohol ethoxylate in a sample mixture.