Development and validation of a high performance liquid chromatography–tandem mass spectrometry for the determination of etodolac in human plasma

A simple and specific method using a one-step liquid–liquid extraction (LLE) with butyl acetate followed by high performance liquid chromatography (HPLC) coupled with positive ion electrospray ionization tandem mass spectrometry (ESI-MS/MS) detection was developed for the determination of etodolac in human plasma, using indomethacin as an internal standard (IS). Chromatographic separation was performed isocratically using a Capcellpak MGII C18 column with 65% acetonitrile and 35% water containing 10 mM ammonium formate (adjusted to pH 3.5 with formic acid). Acquisition was performed in multiple reaction monitoring (MRM) mode by monitoring the transitions: m/z 287.99 > 172.23 for etodolac and m/z 357.92 > 139.01 for IS. The method was validated to determine its selectivity, linearity, sensitivity, precision, accuracy, recovery and stability. The limit of quantitation (LLOQ) was 0.1 μg/mL with a relative standard deviation of less than 15%. The devised method provides an accurate, precise and sensitive tool for determining etodolac levels in plasma.