HPLC-ESI-MS method development for the elucidation of nicardipine degradation products

Purpose: Nicardipine is a member of a family of calcium channel blockers named dihydropiridines that are known to be photolabile and may cause phototoxicity. It is therefore vital to develop analytical method which can study the photodegradation of nicardipine. Method: Forced acid degradation of nicardipine was conducted by heating 12 ml of 1 mg/ml nicardipine with 3 ml of 2.5 M HCl for two hours. A gradient HPLC medthod was developed using Agilent Technologies 1200 series quaternary system. Separation was achieved with a Hichrome (250 x 4.6 mm) 5 μm C18 reversed phase column and mobile phase composition of 70% A(100%v/v water) and 30% B(99%v/v acetonitrile + 1%v/v formic acid) at time zero, composition of A and B was then charged to 60%v/v A;40%v/v B at 10minutes, 50%v/v A; 50%v/v B at 30minutes and 70%v/v A; 30%v/v B at 35minutes. 20μl of 0.8mg/ml of nicardipine degradation was injected at room temperature (25oC). The gradient method was transferred onto a HPLC-ESI-MS system (HP 1050 series - AQUAMAX mass detector) and analysis conducted with an acid degradation concentration of 0.25mg/ml and 20μl injection volume. ESI spectra were acquired in positive ionisation mode with MRM 0-600 m/z. Results: Eleven nicardipine degradation products were detected in the HPLC analysis and the resolution (RS) between the respective degradants where 1.0, 1.2, 6.0, 0.4, 1.7, 3.7, 1.8, 1.0, and 1.7 respectively. Nine degradation products were identified in the ESI spectra with the respective m/z ratio; 171.0, 166.1, 441.2, 423.2, 455.2, 455.2, 331.1, 273.1, and 290.1. The possible molecular formulae for each degradants were ambiguously determined. Conclusion: A sensitive and specific method was developed for the analysis of nicardipine degradants. Method enables detection and quantification of nicardipine degradation products that can be used for the study of the kinetics of nicardipine degradation processes.