Liquid Chromatographic Determination of 4-(2-di-N,N-Propylaminoethyl)-2-(3H)-Indolone in Rat, Dog, and Human Plasma with Ultraviolet Detection

A sensitive, specific, and accurate assay for 4-(2-di-N,N-propylaminoethyl)-2-(3H)-indolone, 1 (SK&F 101468), in plasma was developed using high-performance liquid chromatography with UV detection. The method involves sample preparation by solid-phase extraction, elution of 1 and the internal standard with a volatile solvent, concentration, and reversed-phase chromatography in the presence of an ion-pairing agent. Using 1mL of plasma, 5ng/mL of 1 is detectable and 10ng/mL of 1 can be quantitated. The recovery of 1 and internal standard from plasma is >95%. The within-day precision of this method at 17.5, 219, and 395ng/mL is 3.4, 1.3, and 1.5%, respectively. The between-day precision at these concentrations is 6.0, 1.9, and 2.6%, with a mean accuracy of 100.6, 98.3, and 100.2%, respectively. Stability studies indicate that 1 is stable in plasma at −80°C for ≤180 d.