Bioananalysis of captopril: two sensitive high-performance liquid chromatographic method with pre- or postcolumn fluorescent labeling

Robbert J. Kok, Jan Visser, Frits Moolenaar, Dick de Zeeuw, Dirk K.F. Meijer

Research output: Contribution to journalArticleAcademicpeer-review


This study describes the development and comparison of two HPLC methods for the analysis of the antihypertensive drug captopril. The first method is based on a precolumn derivatization of captopril with the fluorescent label monobromobimane (MBB), The second method is based on a postcolumn reaction with the fluorescent reagent o-phthaldialdehyde (OPA). Since the disulfide metabolites of captopril can be reconverted to the active drug in vivo, the bioanalysis of captopril should involve both the determination of its free thiol form (free captopril) and the total amount of free thiol and reducible disulfides (total captopril). For total captopril analysis, disulfides were reduced with tributylphosphine (TBP) prior to protein precipitation, Since the reducing agent interfered with the MBB derivatization reaction, this method was not suitable for total captopril analysis. Both methods were validated for the bioanalysis of free captopril in human plasma. After removal of plasma proteins, samples were analyzed without an additional extraction procedure. The limit of quantitation in plasma was 12.5 ng/ml for the MBB method (limit of detection 30 pg) and 25 ng/ml for the OPA method (limit of detection 50 pg). The OPA method was also validated for total captopril analysis in human plasma and urine. The limit of quantitation was 25 ng/ml in plasma and 250 ng/ml in urine (limit of detection 50 pg). We conclude that for the analysis of free captopril the precolumn MBB method is superior to the OPA method since only the derivatization reaction has to be carried out immediately. The postcolumn OPA method is especially suitable for the analysis of total captopril since reducing reagents and high concentrations of endogenous thiols do not interfere with the derivatization reaction.
Original languageEnglish
Pages (from-to)181-189
Number of pages9
JournalJournal of Chromatography - Biomedical Applications
Issue number1
Publication statusPublished - 23 May 1997


  • Captopril
  • Monobromobimane
  • o-Phthaldialdehyde
  • antihypertensive agent
  • captopril
  • drug metabolite
  • accuracy
  • animal experiment
  • animal tissue
  • article
  • calibration
  • controlled study
  • derivatization
  • drug blood level
  • drug determination
  • drug urine level
  • extraction
  • fluorescence
  • high performance liquid chromatography
  • human
  • human experiment
  • human tissue
  • intermethod comparison
  • male
  • nonhuman
  • normal human
  • oral drug administration
  • priority journal
  • quantitative assay
  • rat
  • reproducibility
  • procedures


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