Comparison of detection performance of UV and electrochemical detection in NACE for a range of different capillary inner diameters

A systematic comparison of UV and electrochemical detection (ED) in conjunction with NACE has been performed for capillaries with different ids ranging from 75 down to 2 mu m. Ferrocene, (ferrocenylmethyl)trimethylammonium acetate, atropine and scopolamine served as model analytes. All studies were done using an ACN-based nonaqueous electrophoresis buffer. For the comparison of detection performance, particular attention was paid to the absolute and relative LODs for decreasing capillary dimensions. In case of UV detection, a significant increase in relative LODs was typically observed for capillaries smaller than 25 mu m in diameter, while the absolute LODs remained nearly constant over a wide range of capillary dimensions. In contrast, ED showed some increase in relative LODs for capillaries smaller than 10 mu m in diameter, but the absolute LODs decreased over the complete range of capillary diameters studied. It could be demonstrated that the straightforward end-column ED with microdisk electrodes can be applied in conjunction with small id (2 mu m) capillaries. Studies with (ferrocenylmethyl)trimethylammonium acetate using such small capillaries resulted in relative and absolute LODs of 7.5 x 10(-7) and 8 x 10(-18) mol/L, respectively.