Tandem-Column High Performance Liquid Chromatography Separation of Non-Steroidal Anti-Inflammatory Drugs (NSAIDs)

A tandem-column liquid chromatographic method was developed to separate ten non-steroidal anti-inflammatory drugs (Aceclofenac, Aspirin, Carprofen, Celecoxib, Diclofenac, Flurbiprofen, Ibuprofen, Ketoprofen, Naproxen, Salicylic Acid) using an achiral tandem-column configuration under reversed-phase conditions. An NSAID test mix was prepared with 0.5 mg/mL thiourea as a t 0 marker and 0.5 mg/mL of the above NSAIDs in 1:1 acetonitrile: 0.2% formic acid. Three different 5-cm columns were investigated individually and in two different tandem-column configurations: an octyl (C8) column, a perfluorophenyl (PFP) column, and a biphenyl (BP) column. The two tandem configurations investigated were a PFP column followed by either a BP or C8 column. While none of the individual columns provided the selectivity needed to separate two sets of critical pairs (Ketoprofen and Naproxen; Flurbiprofen and Ibuprofen), the unique selectivity provided by the two tandem-column combinations enabled both critical pairs to be separated. The PFP + BP tandem column combination was able to separate the 10 NSAIDs with baseline or greater resolution in less than 25 min.