Zero-crossing derivative spectrophotometry for the determination of haloperidol in presence of parabens

First derivative spectrophotometry with a zero-crossing technique of measurement is used for the quantitative determination of haloperidol in the presence of methylparaben and propylparaben, which is added as antimicrobial preservatives in pharmaceuticals. This technique permits the quantification of haloperidol in the presence of parabens, with closely overlapping spectral bands, and without any separation step. Linear calibration graphs of first derivative values (at 255.2 nm for haloperidol) versus concentration (in the range 4.0-20.0 mu g ml(-1)) were obtained with negligible intercepts. Relative standard deviation of 0.83% was obtained for intra-day precision and 1.86% for inter-day precision. The recovery of haloperidol in synthetic mixtures with parabens and in pharmaceutical dosage forms is also reported. (C) 1998 Elsevier Science B.V. All rights reserved.