Single-calibrant quantification of drugs in plasma and whole blood by liquid chromatography-chemiluminescence nitrogen detection.
Poor availability of drug reference standards may severely complicate clinical and forensic toxicology investigations. To overcome this problem, a new approach is introduced for drug analysis without primary reference standards. Liquid chromatography-chemiluminescence nitrogen detection (LC-CLND) was employed as the analytical technique, based on the detector's equimolar response to nitrogen and using caffeine as single secondary standard. Liquid-liquid extraction recoveries for 33 basic lipophilic drugs were first established by LC-CLND in blood specimens spiked with the respective reference substances. The mean recovery by butyl chloride-isopropyl alcohol extraction for plasma and whole blood was 90+/-18 and 84+/-20%, respectively. The validity of the generic extraction recovery-corrected single-calibrant LC-CLND was then verified with proficiency test samples, including 20 different analyses. The mean accuracy was 24 and 17% for the plasma and the whole blood samples, respectively, and the maximum error was 31% for both specimens. All 20 analyses results by LC-CLND fell within the confidence range of the reference concentrations. LC-CLND proved to be an easy-to-use and robust technique, allowing analysis of 1000 injections of biological extracts without a need for major maintenance operations.
Ojanperä
Suvi
S
Department of Forensic Medicine, PO Box 40, University of Helsinki, Helsinki FI-00014, Finland. suvi.ojanpera@helsinki.fi
Tuominen
Soile
S
Ojanperä
Ilkka
I
D000818:Animals; D002417:Cattle; D002853:Chromatography, Liquid / Q000379:methods*; D006801:Humans; D004364:Pharmaceutical Preparations / Q000097:blood*; D015203:Reproducibility of Results
D004364:Pharmaceutical Preparations