[Application of Q.E.D. and Alco-Screen test kits to measurements of ethanol in forensic samples].

Abstract

We have investigated the applicability of the Q.E.D. (Quantitative Ethanol Detector) and Aloco-Screen test kits for screening ethanol concentrations in forensic samples, such as hemolyzed/decomposed blood, urine and vitreous humor. Because both kits were based on enzymatic color reactions, direct application of the kits to hemoglobin-rich samples gave unsatisfactory results. The deproteinization of blood with trichloroacetic acid followed by membrane filtration overcame such problem. This procedure was also effective for pretreatment of urine and vitreous humor samples to suppress excessive color development in the Alco-Screen test. The ethanol concentrations in whole blood (n = 29), urine (n = 7) and vitreous humor (n = 6) samples determined by the Q.E.D. kit correlated well with those determined by gas chromatography; the correlation coefficients were 0.986, 0.975 and 0.993, respectively. Because of its high specificity and sensitivity to ethanol, Q.E.D. seems to be highly reliable for quantitative estimation of ethanol concentrations in forensic samples. Alco-Screen also had high sensitivity, the specificity to ethanol was relatively low; the color reaction was also observed in the presence of acetone, n-propanol, toluene, methanol, ethylene glycol, methamphetamine, diazepam and dichrovos. Therefore, if forensic samples are analyzed by the Alco-Screen, it is essential to confirm the positive results using other analytical methods.