Rapid and sensitive LC separation of new impurities in trimethoprim

Trimethoprim is a chemotherapeutic often used in combination with sulfonamides. Herein, we report on the development and validation of a new HPLC assay of trimethoprim. The test allows the identification of new impurities that have not been detectable with any other known method including European Pharmacopoeia and USP. Trimethoprim and its impurities were eluted on a C18 column with a mobile phase consisting of methanol and a solution of sodium perchlorate at a flow rate of 1.3 ml/min and was quantified by UV detection at 280 nm. Overall, the method is simple, rapid and reliable for the detection of six impurities in trimethoprim batches.