A selective ultra-performance liquid chromatographic (UPLC) method has been developed for the determination of magnesium valproate and process-related impurities. The method includes an Acquity BEH C18 reversed-phase column with an internal diameter of 100 mm × 2.1 mm and a particle size of 1.7 µ. The mobile phase consists of acetonitrile and 5 mM ammonium dihydrogen orthophosphate with pH = 3.0 and acetonitrile with 45:55 isocratic elution. The flow rate was 0.3 ml/min, and UV detection was performed at 215 nm. A system suitability test (SST) was developed to govern the quality of separation. The developed method was further validated with respect to linearity, accuracy, precision, selectivity, LOD, LOQ and robustness. Several batches of samples were examined using this method, the method was found to be effective when applied to analyze a commercial formulation of magnesium valproate. KEYWORDS Magnesium valproate, ultra-high performance liquid chromatography, process-related impurities, method validation, isocratic elution. Magnesium valproate is chemically known as Magnesium 2-propylpentanoate. Magnesium valproate is an anticonvulsant used in the treatment of epilepsy and bipolar disorder, as well as other psychiatric conditions requiring the administration of a mood stabilizer.[1-6] The chemical structures of magnesium valproate and four of its related impurities its process are shown in Fig. .01. To our knowledge, there is no paper describing an Ultra Performance Liquid Chromatographic (UPLC) method that allows the separation of magnesium valproate and its impurities in bulk drugs. There are some articles on isocratic liquid chromatographic methods for the determination of magnesium valproate.[7, 8] However, these isocratic methods use short columns and are suitable...... middle of paper...... valproate and its related impurities were added to the samples and the recovery was calculated which was between 98 and 102%, well within the acceptance criteria. The precision of the method was evaluated using multiple preparations of a single sample. Six different preparations of the same magnesium valproate and related impurity sample, each 0.20 mg/ml, were analyzed in triplicate on the same day. New solutions were prepared and analyzed on each of the following two days. The % RSD values ​​obtained for the peak areas of magnesium valproate, velaronitrile, pentanoic acid, 2-ethyl pentanoic acid, and 2-(1-methyl, ethyl) pentanoic acid were not greater than 2.0. The intermediate precision study was performed using another Acqity BEH C18 column (100 mm × 2.1 mm in, 1.7μ particle size) and by different analysts. The %RSD values ​​were the same magnitude as above.