Development of a radioimmunoassay for the determination of N-desmethylzopiclone in urine

The development of a specific and sensitive radioimmunoassay for the detection of N-desmethylzopiclone in urine samples is described. The assay will be used to pre-screen for N-desmethylzopiclone as an indication of zopiclone intake in a forensic and emergency context. N-Hemisuccinyldesmethylzopiclone has been prepared as a hapten. The immunization of rabbits with the hapten-bovine serum albumin conjugate resulted in the production of highly specific antibodies, showing no significant cross-reactivities with existing drugs. The four-parameter logistic model was used to process the calibration data into a fitting curve (r2 = 0.9979). Intra- and inter-assay relative standard deviations were < 9.1 and < 19.1%, respectively. The minimum detectable dose of the immunoassay was calculated to be 0.1 ng ml-1 (Pooled-variance t-distribution, p = 0.01, degrees of freedom = 14).