On-line hyphenation of quantum cascade laser and capillary electrophoresis

We report the first successful hyphenation of a Fabry Pérot quantum cascade (QC) laser to a capillary electrophoresis system. This involved use of a dedicated IR-transparent flow cell, made of CaF2, constructed by means of SU-8 based lithography and low temperature wafer bonding techniques. Adenosine, guanosine, xanthosine and adenosine-5′-monophosphate were separated in a borate-containing separation electrolyte (10 mM, pH 9.3). Functional group (carbohydrate) detection was accomplished by use of the 1080 cm−1 emission line of the available QC-laser. The assessable optical path length could be increased, from the normally available 10-15 μm in CE-FTIR analyses, to 60 μm using this powerful mid-infrared laser and aqueous solutions.