Bioanalytical method for the estimation of co‐administered esomeprazole, leflunomide and ibuprofen in human plasma and in pharmaceutical dosage forms using micellar liquid chromatography

The present study represents a connection between basic science and clinical applied science through providing a bioanalytical method for the analysis of certain co‐administered drugs used for the treatment of rheumatoid arthritis. The studied drugs are esomeprazole, leflunomide and ibuprofen. The proposed bioanalytical method is a simple reversed phase high performance liquid chromatographic method using micellar mobile phase. The method is conducted using a Shim‐pack VP‐ODS (150 mm × 4.6 mm ID) stainless steel column at ambient temperature with ultraviolet detection at 285 nm. The micellar mobile phase consisted of 0.1  m sodium dodecyl sulfate, 10% n‐propanol, 0.3% triethylamine in 0.02  m orthophosphoric acid (pH 3.5) and is pumped at a flow rate of 1.0 mL/min. The calibration curve was rectilinear over the concentration range of 0.1–5.0, 0.5–10.0 and 1.0–20.0 μg/mL for esomeprazole, leflunomide and ibuprofen respectively. The proposed method was successfully applied to the analysis of these drugs in dosage forms. The method is extended to the in‐vitro , in‐vivo determination of these drugs in spiked and real human plasma samples.