High-performance liquid chromatographic determination of diclofenac in human plasma after solid-phase extraction

A novel high-performance liquid chromatographic (HPLC) method for the quantification of diclofenac in human plasma was set up. Samples, added with ibuprofen (used as internal standard) were purified by solid-phase extraction using Abselut Nexus cartridges (Varian) not requiring pre-conditioning. Drugs of interest were eluted directly into the autosampler vials and injected. The recovery of diclofenac was 92%, the analysis lasted 7 min with a sensitivity of 5 ng/ml and intra- and inter-day RSDs of 3 and 8%, respectively. The pharmacokinetics of diclofenac after oral and rectal administration in 10 healthy volunteers are reported.