Liquid chromatography–tandem mass spectrometry method for simultaneous determination of valproic acid and its ene-metabolites in epilepsy patient plasma

Abstract

A simple and high throughput method was developed and validated for simultaneous determination of valproic acid and its two toxicant ene-metabolites, 2-enevalproic acid and 4-enevalproic acid in epilepsy patient plasma using liquid chromatography–tandem mass spectrometry. Probenecid was used as internal standard and solid-phase extraction was selected for sample preparation. A chromatographic separation was performed on an Agilent Poroshell SB-C18 column (50 mm×4.6 mm i.d., 2.7 μm) by an optimized gradient elution at a flow rate of 0.9 mL/min. The total run time was 7 min. Electrospray ionization was used in negative ion mode by multiple reaction monitoring of the precursor-to-product ion transitions at m/z 143.0→143.0 for valproic acid, m/z 140.9→140.9 for 2-enevalproic acid and 4-enevalproic acid for their poor fragments, and m/z 283.9→239.9 for probenecid. The results showed good linearity of valproic acid, 2-enevalproic acid and 4-enevalproic acid in their respective linear ranges. The correlation coefficients were more than 0.998. The intra- and inter-day precision of the assay was less than 11.0% and the accuracy ranged from 2% to 12%. This analytical method was successfully applied to assay plasma concentrations of valproic acid and its two ene-metabolites in epilepsy patient plasma and used for therapeutic drug monitoring.

Instantaneous Differentiation of Functional Isomers via Reactive Flowing Atmospheric Pressure Afterglow Mass Spectrometry

“…Conventionally, they can be analyzed using GC–MS or UHPLC/MS, − which is labor-intensive and time-consuming because pre-column derivatization is often needed. LC–MS/MS in the negative-ion mode has been reported for simultaneous determination of VPA with its metabolites including 4-ene VPA . However, it should be noted that differentiation or quantitation of γ-valprolactone is not presented in that study.…”

New Methods Used in Pharmacokinetics and Therapeutic Monitoring of the First and Newer Generations of Antiepileptic Drugs (AEDs)

“…VPA concentrations can be determined by HPLC methods with UV detection [135,136]. Recently, LC methods coupled with MS/MS detection in the negative ion mode were reported allowing to determine VPA and its metabolites 2-ene-VPA, 4-ene-VPA and 2,4-diene-VPA in plasma and serum [137,138]. The analytes are determined using a mixture of an aqueous mobile phase with an organic solvent such as methanol or acetonitrile.…”

“…For further sample purification, LLE is additionally applied using chloroform [134] and n-hexane [135]. Liquid-liquid microextraction (LLME) with chloroform [132,133] and SPE techniques [137,138] are used as well. LOQ of these methods ranging from 0.2 mg/L [132] to 25 mg/L [134] are sufficient for analysis of VPA within the therapeutic range of 50-100 mg/L with appropriate precision and accuracy.…”

Retrospective analysis for valproate screening targets with liquid chromatography–high resolution mass spectrometry with positive electrospray ionization: An omics‐based approach

“…13 Valproate (valproic acid; VPA) is a fatty acid and frequently used anti-epileptic drug, and is therefore generally included in STA in forensic toxicology. 14,15,[17][18][19] Metabolites of VPA have been used for confirmation, 14,17,18 and adducts of VPA with common mobile phase additives enable use of real mass transitions with increased sensitivity. 16 Analysis of VPA using liquid chromatography-tandem mass spectrometry (LC-MS/MS) and LC-HRMS is often performed in negative electrospray ionization mode (ESI − ) with pseudo-multiplereaction monitoring (MRM) transition of mass-to-charge (m/z) 143 → 143, corresponding to the [M-H] − precursor.…”

“…16 Analysis of VPA using liquid chromatography-tandem mass spectrometry (LC-MS/MS) and LC-HRMS is often performed in negative electrospray ionization mode (ESI − ) with pseudo-multiplereaction monitoring (MRM) transition of mass-to-charge (m/z) 143 → 143, corresponding to the [M-H] − precursor. 14,15,[17][18][19] Metabolites of VPA have been used for confirmation, 14,17,18 and adducts of VPA with common mobile phase additives enable use of real mass transitions with increased sensitivity. 20 However, LC-HRMS screening in toxicology is often performed solely using positive electrospray ionization (ESI + ).…”