Comparison of capillary electrophoresis-based immunoassay with fluorescence polarization immunoassay for the immunodetermination of methamphetamine using various methamphetamine antibodies

An accurate and simple immunoassay using capillary electrophoresis (CE) with laser‐induced fluorescence (LIF) was performed for the detection of methamphetamine (MA) in urine. The CE‐LIF was conducted with an untreated fused‐silica column using antiserum and a tracer of fluorescein isothiocyanate (FITC)‐labeled MA. This CE‐LIF system was compared with fluorescence polarization immunoassay (FPIA) in a TDx analyzer in the photo‐check mode using the same FITC‐labeled tracer and the same antiserum. Various antibodies, not only those prepared by our own immunogens but also those from commercial sources, were screened and characterized in both assay systems with regard to sensitivity, precision, and cross‐reactivity. Both systems satisfied analytical precision and gave similar cross‐reactivity patterns. However, the CE‐LIF‐based immunoassay was approximately one order superior to FPIA in sensitivity, requiring less volume of sample, antiserum, and tracer for the assay. Considering that the FPIA system is well known to be a useful tool for screening antibodies and detecting drugs, the CE‐LIF‐based immunoassay system, which is seemingly more advantageous than the FPIA system, appears to have great power for the characterization of antibodies and for the detection of MA in urine.