Gradient RP-HPLC method for the determination of potential impurities in dabigatran etexilate in bulk drug and capsule formulations

A selective RP-HPLC method for separation and determination of potential related impurities (starting materials and by-products of synthesis, and degradants) of dabigatran etexilate (DAB) drug substance has been developed and validated. The separation was accomplished on a Inertsil ODS 3V (250mm×4.6mm, 5μm) column connected to a photodiode array (PDA) detector using 20mM ammonium formate with 0.1% of triethylamine (pH: 5.0 adjusted with formic acid) as mobile phase-A and acetonitrile as mobile phase-B, under gradient elution. Two unknown impurities found in dabigatran etexilate industrial batch stability condition at levels more than 0.1% in HPLC analysis were characterized preliminarily by ESI-MS/MS studies. The major unknown (unknown-1) was enriched and isolated by preparative LC and structure was evidenced by 1H and 13CNMR spectroscopy, mass spectrometry and FT-IR. Another unknown (unknown-2) found as secondary degradant and structure was proposed by ESI-MS/MS study. This method can be used for the quality control of both drug substance and drug product. The performance of the method was validated according to the ICH guide lines for specificity, limit of detection, limit of quantification, linearity, accuracy, precision, ruggedness and robustness.