Direct Automated EMIT® d.a.u. Analysis of N,N-Dimethyl-formamide-Modified Serum, Plasma, and Postmortem Blood for Amphetamines, Barbiturates, Methadone, Methaqualone, Phencyclidine, and Propoxyphene

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Abstract
The addition of two volumes of N,N-dimethylformamide (DMF) to serum, plasma, and postmortem blood with subsequent centrifugation resulted in supernatant that could be directly analyzed by EMIT d.a.u. urine reagents on the Syva autocarousel. Application of this method to the drugs below gave cutoff concentrations in milligrams of immunochemically cross-reactive analyte equivalents/L as follows: 0.05 for amphetamine, 0.05 for secobarbital, 0.075 for methadone, 0.05 for methaqualone, 0.025 for phencyclidine, and 0.05 for propoxyphene. Quantitative “false” negative/positive noncongruence between total EMIT cross-reactants and free-drug analyses by gas chromatography/mass spectrometry were 3/4 (n = 50) for amphetamines, 2/0 (n = 60) for barbiturates, 0/0 (n = 47) for methadone, 0/0 (n = 48) for methaqualone, 1/0 (n = 44) for phencyclidine, and 1/2 for propoxyphene (n = 53). Within-day precision, as indicated by the coefficient of variation, of quantitative estimates using low and high controls ranged from 3.7 to 11% and 1.8 to 10.3%, respectively. Using the same control levels, between-day precision of quantitative estimates varied from 5.8 to 30.3% and 3.0 to 11.8%, respectively.