Comparison of a novel ultra-performance liquid chromatographic method for determination of retinol and alpha-tocopherol in human serum with conventional HPLC using monolithic and particulate columns.

Retinol and alpha-tocopherol are biologically active compounds often monitored in blood samples because of their evident importance in human metabolism. In this study a novel ultra-performance liquid chromatographic (UPLC) method used for determination of both vitamins in human serum has been compared with conventional HPLC with particulate and monolithic C(18) columns. In UPLC a sub-two-micron particle-hybrid C(18) stationary phase was used for separation, in contrast with a five-micron-particle packed column and a monolithic column with a highly porous structure. Methanol, at flow rates of 0.48, 1.5, and 2.5 mL min(-1), respectively, was used as mobile phase for isocratic elution of the compounds in the three methods. Detection was performed at 325 nm and 290 nm, the absorption maxima of retinol and alpha-tocopherol, respectively. Analysis time, sensitivity, mobile-phase consumption, validation data, and cost were critically compared for these different chromatographic systems. Although cost and mobile-phase consumption seem to make UPLC the method of choice, use of the monolithic column resulted in almost the same separation and performance with a slightly shorter analysis time. These methods are alternatives and, in routine laboratory practice, more economical means of analysis of large numbers of biological samples than use of a traditional particulate column.