A rapid and simple procedure for monitoring valproic acid by gas chromatography

Abstract

Valproic acid (VPA), a widely used antiepileptic drug, has a narrow therapeutic range of 50-100 μg/mL and shows large individual variability. It is very important to monitor the trough VPA concentration using a reliable method. The aim of this study was to develop and validate a rapid gas chromatographic (GC) technique for VPA quantification in human plasma and to compare it with the traditional immunoassay method. VPA extraction from human serum was efficient by dichloromethane and hydrochloric acid using octanoic acid as an internal standard. GC analysis was performed using a gas-chromatograph equipped with a flame ionization detector (GC/FID). VPA detection and quantification were accomplished isothermally at 135°C on a Gs-BP 100% dimethylpolysiloxane capillary column (10 m×0.53 mm ID, 2.65 μm film thickness, Supelco, Bellefonte, PA). Injection port and detector temperature were 280°C. Retention times of VPA and internal standard were 1.83 min and 2.33 min, respectively. The calibration curve was linear over the concentration range of 5-320 μg/mL, with a lower limit of detection of 1.25 μg/mL. The internal and inter-day precision was less than 5.3% and 6.1%, respectively, and the accuracy was below 2.8%. VPA recovery was 94.6%. A quick and accurate method for VPA determination in human plasma was developed and validated. It resulted sufficiently selective and sensitive.

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

“…There are several methods for the analysis of VPA and its metabolites in human serum, plasma and saliva. GC methods using capillary columns and nitrogen or helium as a carrier gas are available [132][133][134]. These methods use a flame ionization detector (FID) for detection of the analyte [133,134] and its metabolite 3-heptanone [132].…”

“…GC methods using capillary columns and nitrogen or helium as a carrier gas are available [132][133][134]. These methods use a flame ionization detector (FID) for detection of the analyte [133,134] and its metabolite 3-heptanone [132]. VPA concentrations can be determined by HPLC methods with UV detection [135,136].…”

“…Protein precipitation is performed using trifluoroacetic acid or acetonitrile [132,133]. 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.…”

“…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. Moreover, various commercial reagent-based immunoassay techniques are available, including chemiluminescent microparticle immunoassay (CMIA) and fluorescence polarization immunoassays (FPIA) [139,140].…”

HPLC-UV and GC-MS Methods for Determination of Chlorambucil and Valproic Acid in Plasma for Further Exploring a New Combined Therapy of Chronic Lymphocytic Leukemia

“…It is a well known anticonvulsant drug which nowadays is widely examined for new therapeutic indications [ 13 ]. Analytical methods, such as HPLC [ 14 , 15 , 16 , 17 , 18 ], LC-MS/MS [ 19 , 20 , 21 , 22 , 23 ], gas chromatography (GC) [ 24 , 25 , 26 ] and gas chromatography–mass spectrometry (GC-MS) [ 27 ] were reported for the determination of VPA in biological matrices. Most of the previously reported HPLC and GC methods required complex sample pretreatment or detection, e.g., multistep derivatization for UV detection [ 14 , 17 ], multistep derivatization for fluorimetric detection [ 15 , 16 ], or complex extraction [ 18 , 24 , 25 , 26 , 27 ].…”