EMIT-st drug detection system for screening of barbiturates and benzodiazepines in serum

The determination of barbiturates and benzodiazepines in serum using the EMIT-st drug detection system is reported. The within-day and the day-to-day precision of this assay was investigated by replicate analysis (n = 20) of the serum negative (no drug) and serum positive control of secobarbital (8.0 micrograms/mL) and diazepam (1.0 microgram/mL), respectively. In all cases the coefficients of variation for intra- and interday analysis for both drugs were between 9 and 15%. No temperature influence on the benzodiazepine assay could be observed by running the tests at temperatures ranging from 20 to 25 degrees C as well as at a temperature of 23 degrees C. The specificity and sensitivity of the EMIT-st assay was investigated by measuring various serum concentrations of 14 different barbiturates and 15 different benzodiazepines. A definitive positive response was obtained at a level of 10 micrograms/mL for 5 out of the 14 barbiturates. A positive result at a concentration of 1 microgram/mL was obtained for 10 of the 15 benzodiazepines. A good correlation in response was found for the barbiturates and benzodiazepines compared to the HPLC and GC procedures at concentrations above the detection limit of the assay. In our opinion the EMIT-st tests are useful to clinical toxicological practice. However, the applicability of the screenings test for barbiturates is limited since only a number of these compounds can be detected.