Detection enhancement in nano-channels using micro-machined silicon groove

The present paper reports on an experimental study of the possibility to use a micro-machined detection groove to enhance the detection sensitivity in flat-rectangular nano-channels for ultra-rapid liquid chromatography separations. Transversally running detection grooves with three different axial widths (respectively, 2, 4 and 6 mu m) and one depth (4.75 mu m) were tested in glass and silicon channels for the whole range of detectable fluorescein isothiocyanate isomer 1, FITC, concentrations. The groove with the most square-like cross-section (i.e., 4 mu m wide and 4.75 mu m deep) yielded the best combination of detection gain and minimal additional band broadening. In a 1 cm long channel, the effective plate loss caused by the 4 mu m wide groove would only be of the order of 20%, while the gain in S/N-ratio was of the order of a factor of 5. The detection groove concept yields larger gains in silicon channel substrates than in glass channel substrates, due to the larger stray light losses occurring in the latter.