Журнал аналитических и биоаналитических методов

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Characteristic Features of an Analytical Column with a Pentafluorophenylpropyl Stationary Phase Applied To a Determination of a Fluorinated Phenyl Alanyl Derivative Compound, Gw823093, In Human Urine Using an Lc-Esi-Ms/Ms Method

Harue Igarashi, Shizuko Mogi, Akira Wakamatsu, Yoshiyuki Minamide and Shinobu Kudoh

Pentafluorophenylpropyl (PFPP) stationary phases allow for dipole-dipole, pi-pi, charge transfer and ion- exchange interactions and have shown unique retention of small, polar analytes. PFPP columns are able to retain protonated bases in the presence of high percentages of an organic modifier, which is a suitable condition for liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) analysis. Taking advantage of the characteristics of PFPP columns, a liquid chromatography-electrospray ionization coupled with tandem mass spectrometry (LC-ESI-MS/MS) method was developed to quantify the concentration of a fluorinated phenylalanyl derivative compound, GW823093, in human urine. The analyte is retained with great difficulty on an octadecylsilane- bonded silica (ODS) column, but was strongly retained on a PFPP column in 5 mmol/L ammonium formate buffer (pH 2.9) even with an acetonitrile concentration as high as 80%; these conditions protonated the analyte and enabled higher MS signal intensity. However, the analyte peak shape deteriorated after repeated sample injections when urine samples were analyzed under the selected conditions. To solve this problem, an on-line sample clean-up process with an ODS column was employed before the sample was introduced to the PFPP analytical column. A good peak shape without ion suppression was achieved when using acidified buffer containing 10% acetonitrile as a washing solvent for the process, suggesting that components retained by ionic and weakly hydrophobic interactions were removed. This method was optimized and was linear in quantitation in the range of 25-5000 ng/mL, with a mean coefficient of determination over 0.9998. The validated method was successfully applied to a clinical study of GW823093.