electrospray ionization tandem mass spectrometry quantitative profiling of N-acetylcysteine conjugates of valproic acid in urine: application in drug metabolism studies in humans.
J Mass Spectrom. 2000 Jun; 35(6):698-704.JM

Abstract

We report a GC/NICI-MS assay and a LC/ESI-MS/MS assay for the analysis of N-acetylcysteine (NAC) conjugates of (E)-2,4-diene VPA (NAC I and NAC II) identified in humans. The assay also includes the analysis of the NAC conjugate of 4,5-epoxy VPA (NAC III), an identified metabolite in rats treated with 4-ene VPA for its use in metabolic studies in animals. The highly sensitive GC/MS assay was designed to monitor selectively the diagnostic and most abundant [M - 181](-) fragment anion of the di-PFB derivatives of NAC I, NAC II, and NAC IV, the internal standard (IS) and the PFB derivative of NAC III. The higher selectivity of LC/MS/MS methodology was the basis for an assay which could identify and quantitate the underivatized conjugates simultaneously using MRM of the diagnostic ions m/z 130 and 123 arising from the CID of their protonated molecular ions [MH](+). The GC/MS assay employed liquid-liquid extraction whereas the LC/MS/MS assay used a solid-phase extraction procedure. Linearity ranges of the calibration curves were 0.10-5.0microg ml(-1) by GC/MS and 0.10-1.0microg ml(-1) by LC/MS/MS for NAC I, NAC II and NAC III (r(2) = 0.999 or better). Both assays were validated for NAC I and NAC II and provided good inter- and intra-assay precision and accuracy for NAC I and NAC II. The LOQ by LC/MS/MS was 0.1microg ml(-1), representing 1 ng of NAC I and NAC II. The same LOQ (0.1microg ml(-1)) was observed by GC/MS and was equivalent to 100 pg of each metabolite. NAC III was detected at concentrations as low as 0.01 microg ml(-1) by both methods. The total urinary excretion of the NAC conjugates in four patients on VPA therapy was determined to be 0.004-0.088% of a VPA dose by GC/MS and 0.004-0. 109% of a VPA dose by LC/MS/MS.

Authors+Show Affiliations

Gopaul SV

Faculty of Pharmaceutical Sciences, 214 East Mall, University of British Columbia, Vancouver, BC, Canada V6T 1Z3.

Farrell K

No affiliation info available

Abbott FS

No affiliation info available

MeSH

AcetylcysteineAdolescentAnalysis of VarianceAnimalsAnticonvulsantsChildChild, PreschoolChromatography, LiquidEpilepsyGas Chromatography-Mass SpectrometryHumansMass SpectrometryRatsValproic Acid

Pub Type(s)

Journal Article

Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

10862121

Citation

Gopaul, S V., et al. "Gas Chromatography/negative Ion Chemical Ionization Mass Spectrometry and Liquid Chromatography/electrospray Ionization Tandem Mass Spectrometry Quantitative Profiling of N-acetylcysteine Conjugates of Valproic Acid in Urine: Application in Drug Metabolism Studies in Humans." Journal of Mass Spectrometry : JMS, vol. 35, no. 6, 2000, pp. 698-704.

Gopaul SV, Farrell K, Abbott FS. Gas chromatography/negative ion chemical ionization mass spectrometry and liquid chromatography/electrospray ionization tandem mass spectrometry quantitative profiling of N-acetylcysteine conjugates of valproic acid in urine: application in drug metabolism studies in humans. J Mass Spectrom. 2000;35(6):698-704.

Gopaul, S. V., Farrell, K., & Abbott, F. S. (2000). Gas chromatography/negative ion chemical ionization mass spectrometry and liquid chromatography/electrospray ionization tandem mass spectrometry quantitative profiling of N-acetylcysteine conjugates of valproic acid in urine: application in drug metabolism studies in humans. Journal of Mass Spectrometry : JMS, 35(6), 698-704.

Gopaul SV, Farrell K, Abbott FS. Gas Chromatography/negative Ion Chemical Ionization Mass Spectrometry and Liquid Chromatography/electrospray Ionization Tandem Mass Spectrometry Quantitative Profiling of N-acetylcysteine Conjugates of Valproic Acid in Urine: Application in Drug Metabolism Studies in Humans. J Mass Spectrom. 2000;35(6):698-704. PubMed PMID: 10862121.

* Article titles in AMA citation format should be in sentence-case

TY - JOUR T1 - Gas chromatography/negative ion chemical ionization mass spectrometry and liquid chromatography/electrospray ionization tandem mass spectrometry quantitative profiling of N-acetylcysteine conjugates of valproic acid in urine: application in drug metabolism studies in humans. AU - Gopaul,S V, AU - Farrell,K, AU - Abbott,F S, PY - 2000/6/22/pubmed PY - 2000/8/12/medline PY - 2000/6/22/entrez SP - 698 EP - 704 JF - Journal of mass spectrometry : JMS JO - J Mass Spectrom VL - 35 IS - 6 N2 - We report a GC/NICI-MS assay and a LC/ESI-MS/MS assay for the analysis of N-acetylcysteine (NAC) conjugates of (E)-2,4-diene VPA (NAC I and NAC II) identified in humans. The assay also includes the analysis of the NAC conjugate of 4,5-epoxy VPA (NAC III), an identified metabolite in rats treated with 4-ene VPA for its use in metabolic studies in animals. The highly sensitive GC/MS assay was designed to monitor selectively the diagnostic and most abundant [M - 181](-) fragment anion of the di-PFB derivatives of NAC I, NAC II, and NAC IV, the internal standard (IS) and the PFB derivative of NAC III. The higher selectivity of LC/MS/MS methodology was the basis for an assay which could identify and quantitate the underivatized conjugates simultaneously using MRM of the diagnostic ions m/z 130 and 123 arising from the CID of their protonated molecular ions [MH](+). The GC/MS assay employed liquid-liquid extraction whereas the LC/MS/MS assay used a solid-phase extraction procedure. Linearity ranges of the calibration curves were 0.10-5.0microg ml(-1) by GC/MS and 0.10-1.0microg ml(-1) by LC/MS/MS for NAC I, NAC II and NAC III (r(2) = 0.999 or better). Both assays were validated for NAC I and NAC II and provided good inter- and intra-assay precision and accuracy for NAC I and NAC II. The LOQ by LC/MS/MS was 0.1microg ml(-1), representing 1 ng of NAC I and NAC II. The same LOQ (0.1microg ml(-1)) was observed by GC/MS and was equivalent to 100 pg of each metabolite. NAC III was detected at concentrations as low as 0.01 microg ml(-1) by both methods. The total urinary excretion of the NAC conjugates in four patients on VPA therapy was determined to be 0.004-0.088% of a VPA dose by GC/MS and 0.004-0. 109% of a VPA dose by LC/MS/MS. SN - 1076-5174 UR - https://www.unboundmedicine.com/medline/citation/10862121/Gas_chromatography/negative_ion_chemical_ionization_mass_spectrometry_and_liquid_chromatography/electrospray_ionization_tandem_mass_spectrometry_quantitative_profiling_of_N_acetylcysteine_conjugates_of_valproic_acid_in_urine:_application_in_drug_metabolism_studies_in_humans_ L2 - https://doi.org/10.1002/1096-9888(200006)35:6<698::AID-JMS996>3.0.CO;2-S DB - PRIME DP - Unbound Medicine ER -

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