We present a method for simultaneously determining five anticonvulsants [phenobarbital, phenytoin (diphenylhydantoin), primidone, ethosuximide, and carbamazepine] in as little as 25 microliters of serum. The proteins are precipitated with an acetonitrile solution containing hexobarbital as an internal standard. The anticonvulsants are eluted from a reversed-phase column with a mobile phase consisting of an acetonitrile/phosphate buffer (19/81 by vol) at a flow rate of 3.0 ml/min. The eluted drugs are detected by their absorption at 195 nm, and quantities estimated from their peak heights. Each analysis requires about 14 min. at an optimum column temperature of 50 degrees C. The lower unit of detection for all of these drugs is less than 10 ng. Sensitivities, for serum samples, of 1.0 mg/liter for all the drugs analyzed are attained routinely. Analytical recoveries for the five drugs varied from 97 - 107%, with good day-to-day precision (CV between 3.9 and 5.9%). Of more than 30 drugs tested for possible interference, only ethotoin interferes with the analysis of phenobarbital.

SUMMARY A technique has recently been described by Blanckaert and his colleagues that specifically and accurately quantifies unconjugated bilirubin, diconjugated bilirubin, and the C-8 and C-12 isomers of monoconjugated bilirubin. This technique has now been used to determine the distribution pattern of bilirubin and its ester conjugates in 91 sera from 65 patients with hepatobiliary disease, and the results were compared with two conventional diazo assays. Both diazo assays yielded values for total bilirubin concentration that were markedly and unpredictably higher than those obtained by the new technique, and the direct-reacting fraction by diazo assay showed little or no agreement with the fraction of total ester conjugates determined by the new method. Previous studies using the new method had shown that bilirubin conjugates are undetectable in sera from healthy adults or individuals with Gilbert's syndrome, but they were found in 89 of the 91 present patient sera. The fraction of total serum bilirubin represented by C-& monoconjugates, C-12 monoconjugates, diconjugates, and total ester conjugates was higher in patients with biliary obstruction than in those with parenchymal liver disease, but extensive overlap between groups prevented determination of these conjugated species from being diagnostically useful. Overall, bilirubin ester conjugates in serum consisted of 30% C-8 monoconjugates, 37% C-12 monoconjugates, and 33% diconjugates, while urine contained predominantly diconjugates.

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We describe the general aspects of ion chromatography and how on-line counted ion-exchange techniques can be utilized to determine pyruvic and lactic acids in plasma and vanillymandelic acid in urine. Pyruvate and lactate are extracted from deproteinized plasma by use of an ion-exclusion resin. After elution from the resin, the plasma extract is chromatographed on an anion-exchange column, with 0.66 mmol/L sodium bicarbonate as the mobile phase. The effluent is detected with an electrical conductivity cell. Vanillylmandelic acid is extracted from diluted urine by use of an anion-exchange resin. After elution from resin, the urine extract is chromatographed on an ion-exclusion column, followed by electrochemical detection. We evaluated the procedures for precision, linearity, analytical recovery, intefering substances, and correlation with an established procedure. the combination of a preliminary resin extraction, an ion chromatographic separation, and a conductivity or electrochemical detector results in rapid, specific methods that can be adapted for use in the clinical laboratory. Preliminary data for other organic acids are presented.

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.