Validation of the Cozart Amphetamine Microplate EIA for the analysis of amphetamines in oral fluid

The purpose of this study was to determine the performance characteristics of the Cozart Amphetamine Microplate EIA for detecting amphetamine in oral fluid. Oral fluid samples were collected using the Cozart RapiScan Collection System from 135 volunteer donors from drug treatment clinics. A further 35 oral fluid samples were collected from volunteer donors who were not drug users. The samples were analyzed in the laboratory using the Cozart Amphetamine Microplate EIA and confirmed using gas chromatography-mass spectrometry (GC-MS). The samples were stored frozen until analysis by GC-MS. The intra-assay precision for the Cozart Amphetamine Microplate EIA for amphetamine in oral fluid over forty assays was 2.74-7.1% CV (within assay) and 3.4-7.0% CV (within day). A total of 78 samples were positive for various amphetamines and related designer drugs. The Cozart Amphetamine Microplate EIA, using a cutoff of 45 ng/ml amphetamine equivalents in neat oral fluid, had a sensitivity of 91.7+/-3.3% and a specificity of 95.9+/-1.9% versus GC-MS using a cutoff of 30 ng/ml. A series of potential adulterants of oral fluid were evaluated and shown not to alter the outcome of the test result.     

Using spectral information in forensic imaging

Improved detection of forensic evidence by combining narrow band photographic images taken at a range of wavelengths is dependent on the substance of interest having a significantly different spectrum from the underlying substrate. While some natural substances such as blood have distinctive spectral features which are readily distinguished from common colorants, this is not true for visualization agents commonly used in forensic science. We now show that it is possible to select reagents with narrow spectral features that lead to increased visibility using digital cameras and computer image enhancement programs even if their coloration is much less intense to the unaided eye than traditional reagents. The concept is illustrated by visualising latent fingermarks on paper with the zinc complex of Ruhemann's Purple, cyanoacrylate-fumed fingerprints with Eu(tta)(3)(phen), and soil prints with 2,6-bis(benzimidazol-2-yl)-4-[4'-(dimethylamino)phenyl]pyridine [BBIDMAPP]. In each case background correction is performed at one or two wavelengths bracketing the narrow absorption or emission band of these compounds. However, compounds with sharp spectral features would also lead to improved detection using more advanced algorithms such as principal component analysis.