RP-HPLC method for analysis of diltiazem: Application to drug metal interaction

A simple and rapid high-performance liquid chromatographic (HPLC) method for the determination and quantification of diltiazem from bulk drug, pharmaceutical formulation and human serum has been developed. Shim-pack CLC-ODS (6.0 x 150 mm) column was used for separation at room temperature. Mobile phase consisted of acetonitrile/water (40 60 v/v), pH was adjusted to 2.8 with phosphoric acid and pumped at flow rate of 0.8 mL min^-1 with UV detection at 235nm. Method was linear in bulk drug and serum between the concentration range of 0.5-3.0 μg mL-l and 1.0-5.0 μg mL^-1, respectively, with correlation coefficient of 0.9997. The limit of detection (LOD) and quantification (LOQ) for diltiazem in bulk drug and serum were 0.015 and 0 046, 0.02 and 0.07 μg mL^-1, respectively. Recovery values of diltiazem in bulk drug, dosage form and serum were 99.88-101.15 %, 98.98-101.64 % and 98.99-102.58 %, respectively. The RSD was < 1 in all cases. Interference of other already administered common medicaments such as aspirin, caffeine, nicotine and other serum components were not found. This method was applied in drug metal interaction studies. Drug metal interaction studies were carried out at 37 and 60 °C to monitor the complexation of drug with metal ions. The study was helpful for the determination of drug in therapeutic concentrations inside human body as well its complexation with metal cations. The proposed method is rapid, accurate and selective, because of its sensitivity and reproducibility.