Radioimmunoassay of diazepam in samples of forensic interest

The radioimmunoassay of diazepam in biological fluids is described. The method is particularly applicable to samples encountered in forensic toxicology that may be haemolysed, decmposed and of small volume. The antiserum and tritiated diazepam that are used are commercially available. Polyethylene glycol (mol. wt 6000) is used to separate the bound and free fractons, and the free fracion is counted by extracting the tritiated diazepam into a toluene-based scintillant. Blood samples are extracted with ethyl acetate before analysis but urine samples may be assayed directly. The assay is convenient, quick and virtually specific for diazepam. The results correlate well with those obtained by gas chromatography.