Determination of lamotrigine in whole blood with on line solid phase extraction

A simple, sensitive and reproducible method was developed for the determination of lamotrigine in whole blood with on-line solid phase extraction followed by HPLC separation with UV detection. Whole blood samples were diluted 1:1 with water and then injected directly on a clean-up column dry-packed with 40microm C8 silica and separated on a C18 reversed-phase column (150x4.6mm) at room temperature. The extraction column was activated with methanol and conditioned with phosphate buffer of pH 4.5. Mobile phases consisted of phosphate buffer of pH 4.5 for the extraction column and of phosphate buffer of pH 4.5 - acetonitrile (60:40, v/v) for the analytical column. At a flow rate of 1.0ml/min and a connection time of 1.0min, the complete cycle time was 10.0min. Detection was carried out at 260nm. No internal standard was necessary. The method was linear over concentration range 0.2-20.0microg/ml for lamotrigine. Recovery was 98%. Within-day and between-day coefficients of variation ranged from 1.8 to 6.7%.