Reversed-phase separation of basic tricyclic antidepressants using buffered and fluoroform-enhanced fluidity liquid mobile phases

In an effort to expand the range of applications of enhanced-fluidity liqui d chromatography (EFLC) to strongly polar and basic analytes, fluoroform (C BF..) was investigated as a fluidity-enhancing agent. Fluoroform was chosen due to its high polarity, low viscosity and chemical inertness toward wate r and basic analytes. A group of representative basic compounds, tricyclic antidepressants, covering a wide range of polarity was chosen as model comp ounds. Their retention behavior on a C-18 stationary phase in methanol/phos phate buffer and methanol/phosphate buffer/CHF3 mobile phases was character ized. The chromatographic performance with mobile phase conditions of diffe rent pH, with and without CHF, addition and with addition of triethylamine was studied. The advantages of using CHF3 enhanced and buffered mobile phas es were shown in the much improved chromatographic performance, such as sho rtened analysis time, increased efficiency, lower pressure drop and improve d selectivity. Furthermore. this study demonstrated for the first time, tha t a commercial instrument could be readily utilized for EFLC separations wh ich greatly expands the application range of the EFLC technique and chromat ographic instrumentation. (C) 2001 Elsevier Science B.V. All rights reserve d.