Micellar electrokinetic capillary chromatographic determination of pirfenidone and 5-carboxy-pirfenidone by direct injection of plasma from patients receiving treatment for idiopathic pulmonary fibrosis (IPF)

A micellar electrokinetic capillary chromatographic method, a variant of capillary electrophoresis, was developed for the detection and measurement of pirfenidone and 5-carboxy-pirfenidone by direct injection of plasma from patients under treatment for idiopathic pulmonary fibrosis. To achieve the best separation a 35 mmol/L N-lauroylsarcosine sodium salt surfactant added with a 16 mmol/L sodium 1-heptanesulfonate solution was used as a running buffer. Analytes were eluted in a fairly short time, 7.35 and 9.40 min for pirfenidone and 5-carboxy-pirfenidone, respectively, at 15°C and with an applied voltage of 30 kV in an 80 cm, 75 µm i.d. uncoated fused-silica capillary. In the range of 6.25 to 200 µmol/L, calibration curves exhibited acceptable linearity with the coefficient of determination higher than 0.999. The recovery of analytes spiked in samples of plasma was found to be 95–109% and 93–106% for pirfenidone and 5-carboxy-pirfenidone, respectively. Intra- and inter-day precisions were around 5%. LOD and LOQ for pirfenidone and 5-carboxy-pirfenidone were, respectively, 1.0 and 4.0 µmol/L. The method, applied to measure analytes in six idiopathic pulmonary fibrosis male patients, provided mean concentrations of 68.91±26.31 and 36.21±26.39 µmol/L for pirfenidone and 5-carboxy-pirfenidone, respectively.