High-performance liquid chromatographic determination of iophenoxic acid in serum

Iophenoxic acid (IPA), a marker used to investigate the feeding behaviour of bait-consuming animals has previously been indirectly determined by measuring protein-bound iodine levels in serum or plasma. For the first time a method is reported for the direct determination of IPA in biological fluids. IPA was determined in de-proteinized serum by high-performance liquid chromatography (HPLC) on a C18 column with a mobile phase of acetonitrile-water. Isocratic and gradient systems are described with limits of detection of 0.2 microgram/ml (isocratic) and 0.05 microgram/ml (gradient). Recoveries from fox serum were 85% at 0.5 microgram/ml, 95% at 5 micrograms/ml and 91% at 50 micrograms/ml.