Sequential-injection system for drug-dissolution studies of ibuprofen tablets and sustained-release formulations

An automated system for drug-dissolution studies based on the sequential-injection (SI) technique is described and evaluated for monitoring of dissolution profiles of ibuprofen tablets, sustained-release capsules and controlled-release matrix tablets. The system was composed of a computer-controlled syringe pump and a multi-position selection valve and coupled to a spectrophotometric detector. An 800 mu l test solution in dissolution vessel was aspirated sequentially into a PTFE holding coil via on-line filters. After delivering an aliquot (40 mu l) of each aspirated solution into the transferring line connected to the detector, the residual dissolution solution in the holding coil was fed back to the dissolution vessel to clear the filter and decrease sample consumption. The sampled aliquot was carried to the detector and monitored at 222 nm. Every hour, seven samples run in hexa-replicates were processed with a total of 42 measurements. The system was continuously run for 12 h with an overall relative standard deviation of 2.18% (n=72) at 50% final concentration level of the dissolution solution, which demonstrates the stability and robustness of the automated SI system. (C) 1998 Elsevier Science B.V.