DESIGN AND EVALUATION OF AN AUTOMATED SOLID-PHASE EXTRACTION METHOD DEVELOPMENT SYSTEM FOR USE WITH BIOLOGICAL-FLUIDS

An automated solid-phase extraction method development system, utilizi ng a Zymate XP robot and a custom-designed solid-phase extraction mani fold, has been developed and validated, This system spikes blank liqui d matrix, such as plasma, with solutions containing drug, internal sta ndard, and up to three metabolites, Samples are then buffered or dilut ed with an appropriate reagent, After these samples and corresponding blanks have been prepared, solid-phase cartridges containing selected sorbents are automatically conditioned, Samples are robotically vortex ed and transferred to the conditioned cartridges, and analytes are ext racted. Validation of this robotic system demonstrated acceptable prec ision and accuracy for three types of liquid transfer, including meter ing pump (<6% RSD and RE for greater than or equal to 2.0 mL dispensa tion), syringe-based laboratory station (less than or equal to 2.9% RS D and 0.5% RE for volumes between 0.25 and 1.00 mL), and syringe hands (<3.5% RSD and RE for volumes between 0.10 and 1.00 mL). For two exam ple compounds, the system provided data which effectively distinguishe d good solid-phase sorbents from marginal ones through precision, reco very, and chromatographic selectivity, Solid-phase extraction of these compounds from human plasma gave precision (2-10% RSD) and extraction efficiency (96 +/- 6%) comparable to results obtained from manual ext ractions (92 +/- 11%).