Assays - Nifedipine

HPLC determination of Nifedipine in plasma on normal phase

Author: H.J. Mascher und H. Vergin
Publisher: Chromatographia 25 (1988), 919-922

For the determination of nifepidine in plasma a sensitive and selective method is required. the use of on-line pre-column enrichment, followed by reversed phase separation and UV detection at 350 nm proved to be too susceptible. Therefore, detection was carried out after a post-column on-line reduction and photoreaction step using a fluorescence detector. Although this method proved to be extremely sensitive (limit of detection 0.1 ng/ml plasma) and selective, a number of problems cropped up caused by the reduction agent which finally prevented the procedure being used in routine analysis. As a consequence, the following method was developed. After liquid-liquid extraction of nifepidine 1/3 of the extract was chromatographed on a normal phase (diOH) system and detected at 235 nm, because detection at 350 nm was not sensitive enough. This method has a limit of detection of 1 ng nifepidine / ml plasma and the calibration curve is linear up to 320 ng/ml. The recovery lies around 82 % and the standard deviation for the range 6 - 320 ng/ml is less than 5 %. So far about 2000 plasma samples have been analysed by this method.