Paul A. Bombardt

High Performance Liquid Chromatographic Determination of Triazolam in Human Serum

Abstract A high performance liquid chromatographic method which utilizes UV-detection has been developed for the sensitive and specific determination of triazolam in human serum. Using 8-chloro-6-phenyl-l-ethoxymethyl-4H-s-triazolo[4, 3-a][1, 4]benzodiazepine as an internal standard, serum samples were buffered with 2 ml of 4M NaOH and extracted twice with 5 ml aliquots of toluene. The combined toluene extracts were evaporated to dryness and the residue dissolved in the chromatographic mobile phase. The samples were chromatography on a microparticulate reverse-phase column using a 0.06M acetic acid:acetonitrile (61:39) mobile phase. Known metabolites of triazolam did not interfere in the analysis. A linear relationship between peak height ratios and concentrations was observed, with the lower limit of detection being approximately 1 ng of triazolam. The utility of the method was demonstrated by administering therapeutic doses of the drug to human volunteers and monitoring serum triazolam concentrations as...

Determination of Cefpodoxime Levels and Cefpodoxime Stability In Human Urine By Direct Injection HPLC with Column-Switching

Abstract A semi-automated method providing on-line sample extraction and quantitative analysis for cefpodoxime in human urine, injected directly into the HPLC, is reported. Samples were filtered by the analyst, injected into the HPLC system with an autosampler and loaded onto a 3 cm RP-18 precolumn with a mobile phase consisting of 10% methanol in 0.2% phosphoric acid and then automatically eluted onto a RP-18 analytical column using a mobile phase containing 7% acetonitrile in pH 5.2 sodium acetate buffer. the mean between-day precision of the standards was ± 4.29%. Spiked urine control recovery averaged 96 ± 6% for controls ranging from 1.0 to 20.0 μg/mL. the limit of quantitation for the method was 0.11 μg/mL.

An on-line, column-switching high-performance liquid chromatographic procedure for the removal of probenecid from human plasma, serum, or urine in the quantitative determination of cefmetazole or cefoxitin

Both cefmetazole sodium (derivative of cephamycin C) and cefoxitin (cephalosporis derivative) are eliminated in man primarily via renal tubular secretion. Thus their half-lives would be expected to be prolonged throught the preadministration of probeneid. A procedure to remove probenecid from clinical biomatrix specimens to allow quantitation of the desired antibiotic, would appear to have wide application in the bisanalytical field

High Performance Liquid Chromatographic Assay for Adinazolam Mesylate in Rodent Feed Mixtures

Abstract Adinazolam mesylate was recovered from the feed mixtures by repeated extraction with a pH 4 citrate buffer. The pooled extracts were diluted with water when necessary and mixed with an equal volume of an acetonitrile solution of internal standard (naphthalene). After mixing and centrifugation, the clear supernates were separated for chromatography. The chromatography was carried out on a reverse phase column using a mixture of phosphate buffer, acetonitrile and methanol in the volume ratios of 85:40:20 as mobile phase. Adinazolam and the internal standard were eluted from the columns at about 11.7–12 and 15.50–17.5 minutes, respectively. The peak height ratios and adinazolam mesylate concentrations showed excellent linearity (r>0.999). Extracts of blank feed samples did not show interference to the assay. Assay results with satisfactory accuracy and precision were obtained. The methodology was applicable for the assay of the drug-feed mixtures containing 0.02 to 10.0 mg of adinazolam mesylate per...

Fast-LC determination of 1-methyl-1H-tetrazole-5-thiol in human plasma with column-switching sample clean-up

A simple, fast and sensitive method for the quantitative determination of 1-methyl-1H-tetrazole-5-thiol using HPLC is reported. Samples are deproteinated by plasma water filtration and injected into a HPLC system capable of column switching and backflushing the analytical column. The limit of quantitation was determined to be 70 ng ml-1 and the limit of detection 22 ng ml-1. Between-day precision (expressed as percent coefficient of variation) of standard curve slopes was +/- 3.5% with a range of within-day percent coefficient of variations from 0.28 to 1.4%. Recovery and precision of spiked control samples was 96 +/- 7% over a concentration range of 630-6300 ng ml-1.