Amperostatic-potentiometric detection for Micro LC

The current trend of separation science is towards miniaturization. Micro separations such as microcolumn liquid chromatography (Micro LC) and capillary electrophoresis have gained considerable importance over the past decade. The early developments of Micro LC were mainly due to the efforts of Horvath and coworkers [1,2], Ishii et al. [3, 4], Scott and Kucera [5, 6], and Novotny et al. [7, 8]. Since then, the field of Micro LC has been steadily growing. Higher column efficiencies, lower mobile phase flow rates, less consumption of mobile and stationary phases, and increased mass sensitivity due to smaller peak volumes are some of the appealing advantages of Micro LC [9, 10]. Also, Micro LC is ideal for the analysis of complex sample mixtures such as exotic physiological fluids and the contents of a single cell [11,12].

In order to maintain the separation efficiency obtained from Micro LC, extra-column volume in injection, detection and connection systems should be minimized [10]. While injectors are commercially available to inject appropriately small amounts of sample (60 - 100 nL), connecting tubing should be minimized wherever possible in order to reduce the extra-column broadening. The maximum permissible detector volume for a 250 |im I.D. column packed with 5 |im particles is 400 nL [10]. Smaller capillaries demand even lower detector volumes.