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A specific, high performance liquid chromatographic method was developed for the assay of haloperidol, together with an adequate separation of its degradation products. The method is based on the use of an octadecylsilane stationary phase column under isocratic conditions. The mobile phase consisted of 50 mM sodium phosphate monobasic pH 2.5-acetonitrile-THF-TEA (63:34:3:0.1, v/v/v/v) adjusted with o-phosphoric acid to a pH of 2.5. The degradation was performed in hydrochloric acid, sodium hydroxide and hydrogen peroxide. The main degradation products were identified. Application of the assay of haloperidol in tablet formulations is presented.

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 micrograms 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 pharmaceutical dosage forms is also reported.