Determination of morphine by capillary electrophoresis immunoassay in thermally reversible hydrogel-modified buffer and laser-induced fluorescence detection

In this paper thermally reversible hydrogel used as a replaceable packed material for capillary electrophoresis was examined. A simple and rapid method of detecting morphine was developed, which demonstrated the potential of strong affinity antibodies as a selector for immunologically-based separations in serum by capillary electrophoresis. Polyclonal antibodies were linked to hydrogel and applied to the separation of free fluorescein isothiocyanate (FITC)-labeled antigen and bound FITC antigen. The separation was monitored with laser-induced fluorescence detection. Different separation conditions were studied. The results indicated that poly-N-isopropylacrylamide hydrogel (PNIPA) is a kind of steady, replaceable gel. The specific determination of morphine did not require a long incubation time and PNIPA hydrogel-modified antibodies can be stockpiled at 4°C before assay. It can be used to determine morphine with good precision and a detection limit lower than 8.5 ng/ml. Details of the preparation of hydrogel cross-linked polyclonal antibody and of typical separations of bound and free antigen are presented.