Determination of ethyl-p-hydroxybenzoate in sow pancreatic juice by reversed-phase high-performance liquid chromatography

We have developed a high-performance liquid chromatographic–UV–Vis–diode-array detection (HPLC–DAD) method for the determination of ethyl-p-hydroxybenzoate, a hydrolytic degradation product of the synthetic protease inhibitor, gabexate-mesilate ethyl-p-(6-guanidinohexanoyloxy) benzoate methanesulfonate (GM) (FOY) in sow pancreatic juice. Methyl-p-hydroxybenzoate (I) was used as the internal standard. The pancreatic juice was deproteinised by acetonitrile and the analytes were chromatographed on a reversed-phase C18 LC column using the gradient elution method. The mobile phase consisted of a solution of 0.017 M orthophosphoric acid and another solution of acetonitrile–water (80:20, v/v). The wavelength of detection was 237 nm. The limit of quantification of the method was 0.20 μM at a 9:1 signal-to-noise ratio. The overall intra- and inter-day accuracy (relative error, RE) ranged from 14.2 to 8.3% and from 13.3 to 9.8, respectively. The overall intra- and inter-day precision (relative standard deviation, RSD) ranged from 7.6 to 2.62% and from 6.7 to 3.1%, respectively. The method proved to be sensitive, specific, accurate and precise and was successfully used to determine the ethyl-p-hydroxybenzoate (II) in sow pancreatic juice.