Performance of a pentafluorophenylpropyl stationary phase for the electrospray ionization high-performance liquid chromatography–mass spectrometry–mass spectrometry assay of cocaine and its metabolite ecgonine methyl ester in human urine

A pentafluorophenylpropyl (PFPP) bonded silica column has been used for the high-performance liquid chromatography–electrospray ionization–mass spectrometry–mass spectrometry assay (HPLC–ESI-MS–MS) of cocaine (COC) and its metabolite, ecgonine methyl ester (EME) in human urine. COC and EME were used as model basic solutes to demonstrate that a PFPP phase yields excellent results for the assay and validation of drugs in biological fluids. The assay was linear over three orders of magnitude (1.0–1000 ng/ml) and precision and accuracy of the assay was 4 and 15%, respectively. The limit of detection (LOD) for COC and EME was 1.6 and 2.8 pg on column, respectively. In addition, only a simple 1:10 dilution of the urine was necessary for the sample preparation procedure thus saving time on a laborious extraction step. The major advantage of the PFPP phase was the enhancement of the ESI-MS signal by providing good retention and good peak shape of COC and EME with a mobile phase of 90% acetonitrile. The MS signal for COC was a factor of 12 times greater on the PFPP phase than on the C18 phase.