Development and validation of UV spectrophotometric method for estimation of regioisomeric impurity in Felodipine bulk and formulation

Abstract

The process related impurity of Felodipine i.e: Diethyl-4 (2-chlorophenyl) 2,6 dimethyl-1,4-dihydro pyridine 3,5 dicarboxylate was synthesized , characterized and quantified in bulk and formulation. The synthesis of intermediate was carried out by Hantzch process using O-chlorobenzaldehyde, ethylacetoacetate, in presence of ammonia and methanol as a catalyst. The percentage yield was found to be 78 %. Recrystallization and purification of FI was done. The preliminary evaluation was done on laboratory scale via melting point, elemental analysis and TLC. The melting point of impurity was found to be 136-140 ⁰ C. The TLC of impurity was carried by using Benzene: Methanol (6:1) and the R _f was found to be 0.64.The regioisomeric impurity was synthesized, purified, and characterized by IR, NMR and UV method was developed for quantification of synthesized impurity. The method was validated as per ICH Q2B guidelines. The UV method was found to be linear, precise, accurate, robust and rugged. Finally Diethyl-4 (2-chlorophenyl) 2,6 dimethyl-1,4-dihydro pyridine 3,5 dicarboxylate impurity was quantified from Felodipine bulk and its marketed tablet formulation.