Separation and identification of polymeric dispersants in detergents by two-dimensional liquid chromatography.

Polymeric dispersants are an important ingredient in many consumer products. Their separations and identifications in final product formulation can be very challenging due to the presence of multiple polymeric dispersants at different levels and the presence of other polymeric and small-molecule components. In this study, using nearly comprehensive two-dimensional liquid chromatography (2D-LC), various water-soluble polymer and co-polymer dispersants were separated with aqueous size exclusion chromatography (SEC) in the first dimension (D) and gradient elution reversed-phase liquid chromatography (RPLC) in the second dimension (D). Detection of the polymeric dispersants was accomplished by evaporative light scattering detector (ELSD). A large ID (8.0 mm) SEC column used in common one-dimensional SEC practices was directly adopted in the 2D setup for rapid method development. A close representation of fully comprehensive 2D separation was achieved even with 60% of D eluent diverted to waste, demonstrating the flexibility and versatility of having SEC in D for two dimensional separation of polymers. Important method parameters, such as D column dimensions and flow rate, gradient conditions, and buffer pH were studied. Practical aspects of routine industrial applications such as solvent consumption and analysis time were also considered. This method was exploited for quick identification of polymeric dispersants in commercial detergent samples. Nine detergent samples were screened and polymeric dispersants and additional polymer features were detected in the samples.