Rapid method for screening toxic drugs in serum with liquid chromatography

We present a method for the simultaneous analysis of a variety of commonly abused drugs (acetaminophen, theophylline, salicylate, primidone, methyprylon, phenobarbital, butabarbital, ethchlorvynol, butalbital, chlordiazepoxide, pentobarbital, amobarbital, phenytoin, glutethimide, secobarbital, flurazepam, nitrazepam, methaqualone, N-desmethyldiazepam, and diazepam) in serum or plasma. Serum proteins are precipitated with an acetonitrile solution containing hexobarbital, the internal standard. The drugs are eluted from a reversed-phase column with a mobile phase consisting of acetonitrile/phosphate buffer (pH 3.2), using a two-step linear gradient, at a flow rate of 3.0 mL/min. The eluted drugs are detected by their absorption at 210 nm; their quantities are estimated from their peak heights. A complete analysis requires no longer than 45 minutes at the optimum column temperature of 50 degree C. A sensitivity of 2 mg/L of serum is attained routinely for most of the hypnotic and analgesic drugs; while methaqualone, chlordiazepoxide, diazepam, and N-desmethyldiazepam can be detected at a concentration of 0.2 mg/L. Analytical recoveries for the twenty drugs varied from 93-112%, with good reproducibility. Of more than forty drugs tested for possible interference, desmethyldoxepin, procainamide, phenylpropanolamine, mesantoin, and phenacetin interfere with the analysis of flurazepam, acetaminophen, ethchlorvynol, and phenobarbital, respectively.