Research Article DEVELOPMENT AND VALIDATION OF RP-HPLC METHOD FOR ESTIMATION OF VALPROIC ACID IN DISSOLUTION STUDY OF ITS FORMULATION MUGDHA KARDE* 1 , HARSHAL PAWAR 2 , RACHEL GEEVARGHESE 3 , JAIKISHAN KHATRI 4 1 Pharmaceutics, Dr. L.H. Hiranandani college of Pharmacy, Smt. CHM College Campus, Opp. Railway Station, Ulhasnagar – 421 003, Dist. Thane (Maharashtra), India, 2 Department of Pharmacognosy, 3,4 Department of Pharmaceutics, Dr. L.H. Hiranandani college of Pharmacy, Smt. CHM College Campus, Opp. Railway Station, Ulhasnagar – 421 003, Dist. Thane (Maharashtra), India. Email: mugdha.karde@yahoo.com Received: 16 Jun 2012, Revised and Accepted: 25 July 2012 ABSTRACT A simple, precise and reproducible reverse phase, isocratic high performance liquid chromatographic (HPLC) method was developed and validated for the quantitative determination of Valproic Acid in the dissolution study of Pharmacosomes. The quantification was carried out using a Zorbax Eclipse XBD- C18 (4.6 × 150mm, 5 μm) column, with a mobile phase consisting of Acetonitrile: Citric acid buffer (50:50, v/v) (pH 3) at a flow rate of 1.5 ml/min and UV detection at 210 nm. The method was validated for specificity, method precision, linearity, recovery, robustness, ruggedness and solution stability. The linearity of the proposed method was investigated in the range of 50-400 μg/ml (r = 0.9997). The proposed method was successfully applied for determination of the Valproic Acid in dissolution study of Pharmacosomes. Keywords: Valproic Acid, Pharmacosomes, Dissolution, Reversed-phase, HPLC. INTRODUCTION Valproic Acid (2-propylpentanoic acid) is an anticonvulsant used to control seizures. Its structure is different from most of the other antiepileptic drugs. Its molecular formula is (CH3CH2CH2)2CHCOOH and molecular weight is 144.2 1 . Valproic acid is classified as Class I drug, even though it is slightly soluble in water (1.3mg/ml). It is very soluble in acetone, methanol, alcohol, chloroform, benzene, ether, organic solvents, miscible with dichloromethane and dissolves in dilute solutions of alkali hydroxides. It is available as slightly viscous clear liquid with boiling point of 220°C 1 . Fig. 1: Structure of Valproic Acid 2 Valproate is believed to affect the function of the neurotransmitter GABA in the human brain. Valproic acid inhibits GABA transaminase by binding to it and thus enhances the neurotransmission of GABA in brain 3, 4 .Valproic acid also blocks the voltage-gated sodium channels and T-type calcium channels. These mechanisms make Valproic Acid a broad-spectrum anticonvulsant drug. Valproic Acid has been used in combination with Sodium Valproate. These formulations show smaller differences in the pharmacokinetics and accessibility in market 5 . Valproic Acid single or in combination with sodium Valproate is available in different dosage forms; capsule, tablet, enteric-coated tablet, sprinkle, liquid, intravenous, suppository and controlled-release formulations 6 . The methods reported in monographs for the assay and dissolution of Valproic Acid is gas chromatography 7,8 . Many other methods are also used for the estimation of Valproic Acid, this involves, high throughput LC- MS 9 , high-performance liquid chromatography (HPLC) with MS detection 9,10 , and high-performance liquid chromatography (HPLC) with fluorescence detection 11 , isotope- dilution mass spectrometry 12 , capillary electrophoresis 13 . Literature survey revealed that no such simple RP-HPLC method is reported for the estimation of Valproic Acid in dissolution study of its formulation like pharmacosomes 14 . The objective of the present study was to develop a simple, less time consuming and economical analytical method for estimation of Valproic Acid in dissolution study of its formulation. MATERIALS AND METHODS Reagents and chemicals Valproic acid USP (Purity = 99.8%) was obtained from Ipca pharmaceuticals, Mumbai as gift sample. The formulation of pharmacosomes was prepared in the Pharmaceutics research laboratory of Dr. L. H. Hiranandani college of Pharmacy. Acetonitrile (HPLC grade, Merck), Citric acid monohydrate (GR, Merck), dibasic sodium phosphate(GR, Merck) were procured from SR Traders. Orthophosphoric acid (88% GR, Merck), sodium hydroxide (analytical grade), potassium dihydrogen phosphate (Molychem) and water (HPLC grade) were used during analysis. Instrumentation Agilent 1200 series integrated high performance liquid chromatographic system equipped with quaternary pump, manual sampler, single wavelength detector, column thermostat and controlled by Chem-Station software was used for HPLC analysis. The Zorbax Eclipse XBD- C18 (4.6 × 150mm, 5 μm) analytical column was used as a stationary phase. Formulation Development The pharmacosomes (Strength: 250mg) of Valproic Acid were prepared by thin film hydration method. The excipients used were soya phosphatidylcholine (Lipoid Gm, Germany) and Cholesterol (analytical grade). The drug lipid complex was dissolved in dichloromethane of analytical grade and evaporated in rotary evaporator to get the thin film which was further hydrated to obtain the vesicles 15, 16 . These vesicles were dried and used for the further analysis. The assay of the prepared pharmacosomes was performed using previously validated analytical method and the contents results were used to calculate the percentage release on each time of dissolution profile. Dissolution Study Dissolution test of prepared Valproic Acid formulation was performed in Electrolab dissolution test system (n=6), dissolution                                            