method validation. Internal standard Salicylic acid.

This research paper describes a procedure for determination of valproic acid (VA) in human serum using salicylic acid (SA) as internal standard (I.S.). The two drugs were separated by using 60% acetonitrile and 40% acidified water with phosphoric acid adjusted pH to 3 ±0.1 as mobile phase.  The column employed was C18 150×4.65µm at ambient temperature. Detection wave length, 220nm, flow rate 1ml/min. injection volume,20µL The method was linear over the range of 10-100ug/ml valproic acid. The validated limit of quantification and the limit of detection for valproic acid were11,1 and 1.11ug/ml, respectively. The precision of the method was evaluated and the intra and the interday precision were found to be 0.2 and 2.0, respectively.  The method is simple rapid, sensitive, robust and accurate and can be used for therapeutic drug monitoring (TDM).