Determination of the antihypertensive drug cilazapril and its active metabolite cilazaprilat in pharmaceuticals and urine by solid-phase extraction and high-performance liquid chromatography with photometric detection

A liquid chromatographic method with photometric detection for the determin ation of cilazapril and its active metabolite and degradation product cilaz aprilat in urine and pharmaceuticals has been developed. The chromatographi c method consisted of a mu Bondapak C-18 column maintained at 30 +/-0.2 deg reesC, using a mixture of methanol-10 mM phosphoric acid (50:50 v/v) as mob ile phase at a flow-rate of 1.0 ml/min. Enalapril maleate was used as inter nal standard. The detection was performed at a wavelength of 206 nm. A stud y of the retention of cilazapril and cilazaprilat using solid-liquid extrac tion has been carried out in order to optimise the clean-up procedure for u rine samples, which consisted of a solid-liquid extraction using C-8 cartri dges. Recoveries greater than 85% are obtained for both compounds. The meth od was sensitive, precise and accurate enough to be applied to the determin ation of urine samples obtained from three hypertensive patients up to 24 h after intake of a therapeutic dose (detection limit of 70 ng/ml for cilaza pril and cilazaprilat in urine). A comparison of the method developed using photometric and amperometric detection has been carried out. (C) 2001 Else vier Science B.V. All rights reserved.