Comprehensive two-dimensional liquid chromatographic method (Chiral × Achiral) for the simultaneous resolution of pesticides.

This work demonstrates the potential of two-dimensional liquid chromatography (2D-LC) to increase the resolution capacity of multiple pesticides in a single analysis of samples that contain both chiral and achiral compounds. The setup is based on the combination of a chiral column in the first dimension and an achiral column in the second dimension using the on-line full comprehensive mode (LC × LC). This method was optimized for the separation of 24 pesticides (17 chiral and 7 achiral). The 2D-LC system was built with an active flow splitter pump in order to easily adjust the volume of sample transferred to the second dimension and to select and optimize independently the flow rate in the first dimension. The first-dimension optimization involved the comparison of enantioresolution abilities of three different polysaccharides chiral stationary phases as well as different elution conditions, while in the second-dimension parameters like stationary phase and organic modifier were explored. Other experimental variables that influence the two-dimensional peak capacity (orthogonality, sampling frequency, shift gradients, etc.) are discussed.