Environmental analysis by on-line immunoextraction and reversed-phase liquid chromatography: optimization of the immunoextraction/RPLC interface.

The use of antibodies in HPLC columns for on-line immunoextraction combined with reversed-phase liquid chromatography (RPLC) is of growing interest in environmental and agricultural analysis. This technique is typically performed by using a small RPLC precolumn to capture and concentrate analytes as they elute from the immunoextraction column; however, there is little information on the conditions required for optimizing this interface. This study examined the behavior of this interface by using 2,4-dichlorophenoxyacetic acid (2,4-D) and related herbicides as model analytes. It was found that analyte dissociation from immunoextraction columns followed first-order decay and that the elution of these analytes through the immunoextraction/RPLC interface gave an exponentially modified Gaussian profile. Computer simulations were used to see how analyte elution through the interface changed with different dissociation and retention conditions. Several guidelines were developed from this work that could be used for developing and optimizing on-line immunoextraction/RPLC systems for other chemicals of environmental or agricultural interest.