Ion chromatographic determination of residual phase transfer catalyst in active pharmaceutical ingredient

A new ion chromatography method with non-suppressed conductivity detection has been developed for the quantification of residual phase transfer catalyst-tetrabutylammonium bromide (TBAB) in an active pharmaceutical drug, Levetiracetam. Separation conditions are optimized to get a clear separation of TBAB from drug impurities using a Metrosep Cation C2-150 column. Conditions are also optimized to separate tetramethylammonium bromide, tetraethylammonium bromide, and tetrapropylammonium bromide, which are also used as phase transfer catalysts in several syntheses. Method performance was checked for selectivity, linearity, limit of quantification, limit of detection, accuracy, and precision. The method has superior performance with linearity r(2) > or = 0.9999, recovery from 94.7% to 96.5%, precision < or = 0.74%. In-line preconcentration is used to achieve limits of detection and quantification of 39 ng and 118 ng of TBAB, which corresponds to 1.56 and 4.72 microg/g of TBAB with respect to sample weight. The proposed method can be used for routine quality assurance analysis in the pharmaceutical industry.