Enantioselective analysis of fluoxetine and norfluoxetine in plasma samples by protein precipitation and liquid chromatography with fluorescence detection

Abstract

In this study, the enantioselective analysis of fluoxetine and norfluoxetine in plasma samples was performed by the protein precipitation method and high performance liquid chromatography with fluorescence detection (PP/LC-FD). Different precipitating agents - organic solvents, acids, and salts - in several proportions were available. The Bradford colorimetric method employed for evaluation of the efficiency of protein precipitation, has shown that for the sake of simplicity and percentage of protein precipitation (99.7%), acetonitrile was most effective when added at a ratio of 3:1 (acetonitrile/plasma, v/v). The quantification limit of the PP/LC-FD method was 30 ng mL-1 for the four enantiomers. The response of the proposed method was linear over a dynamic range from LOQ to 1000 ng mL-1, with correlation coefficients higher than 0.9973. In conclusion, the PP/LC-FD method can be successfully used to analyze plasma samples from ageing patients undergoing therapy with fluoxetine. © 2011 Sociedade Brasileira de Química.