Liquid exclusion–adsorption chromatography: a new technique for isocratic separation of non-ionic surfactants: V. Two-dimensional separation of fatty acid polyglycol ethers

Fatty acid polyglycol esters can be fully characterized using two-dimensional liquid chromatography with liquid chromatography under critical conditions (LCCC) as the first and liquid exclusion–adsorption chromatography (LEAC) as the second dimension. LEAC is run under isocratic conditions, which allows the use of the refractive index detector, and thus accurate quantitation. Fractions from LCCC are transferred to LEAC using the full adsorption–desorption technique, by which they are focussed and reconcentrated before injection into the second dimension. This is achieved by increasing the water content of the mobile phase behind the LCCC column. Monoester oligomers of up to 20 oxyethylene units can be resolved to the baseline. Diester oligomers are partially separated in the first dimension (LCCC).