Rapid, Selective and Rugged Method Development and Validation of Diltiazem and its Metabolites, N-Desmethyl Diltiazem, Desacetyl Diltiazem in Human plasma using Liquid Chromatography coupled with Tandem Mass Spectrometry.

A simple, sensitive, selective and rugged liquid chromatography coupled with mass spectrometry (LC/MS/MS) method for quantification of Diltiazem and its metabolites, N-desmethyl Diltiazem, desacetyl Diltiazem in human plasma was developed and validated. The chromatography was developed using Luna 5 μ, C18, 100×4.60 mm column having a mobile phase of Acetonitrile: 0.1 % formic acid (85:15 % v/v). The flow rate was 0.5 ml/min at a column temperature of 50 ± 5º C. Electron spray ionization technique in positive mode was selected to improve the selectivity and sensitivity required for this application. The retention times of Diltiazem, desmethyl Diltiazem, desacetyl Diltiazem were 2.5, 2.0 and 2.5 minutes respectively. The method was validated for linearity, precision, accuracy, specificity, sensitivity, matrix effect, dilution integrity, ruggedness, injection reproducibility and stability. Calibration curves during the course of validation were found to be linear for Diltiazem, desmethyl Diltiazem, desacetyl Diltiazem in the ranges of 0.604-603.902, 0.303-303.274 and 0.299-299.489 ng/mL with correlation coefficient ≥ 0.9969, 0.9958 and 0.9970 respectively and by using a 1/x2 weighted least square regression analysis of standard plots associated with ten point calibration standards. The precision and mean accuracy were within the acceptable limits.