Separation and on-line distinction of enantiomers: a non-aqueous capillary electrophoresis Fourier transform infrared spectroscopy study.

We report on the separation and on-line distinction of (R,S)-3,5-dinitrobenzoyl leucine (DNB-Leu) enantiomers with non-aqueous capillary electrophoresis (CE) and Fourier transform infrared (FT-IR) spectroscopic detection using O-(tert-butyl carbamoyl) quinine (tBuCQN) as the chiral selector (CS). Due to stereoselective intermolecular interactions--particularly ionic interactions, hydrogen bonding, and pi-pi-interactions--the enantiomers undergo enantioselective complex and ion-pair formation, respectively, with the CS enabling CE separation and direct identification with FT-IR detection. Especially the (S)-enantiomer of the analyte shows significant changes in the mid-infrared region upon complexation, allowing for a clear spectral distinction between both enantiomers.

Time-resolved Fourier transform infrared spectrometry using a microfabricated continuous flow mixer: application to protein conformation study using the example of ubiquitin.

We report on the use of time-resolved Fourier transform infrared spectroscopy (FT-IR) to study chemically induced conformational changes of proteins using the example of ubiquitin. For this purpose a micromachined mixer is coupled to a conventional IR transmission cell with a pathlength of 25 microm and operated in both the continuous and the stopped-flow mode. This experimental set-up allows the elucidation of reaction pathways in the time frame of about 500 milliseconds to seconds with little reagent consumption and low pressure.

Micellar electrokinetic chromatography with on-line Fourier transform infrared detection.

Micellar electrokinetic chromatography (MEKC) was successfully coupled to Fourier transform infrared (FTIR) detection, using a micromachined IR-transparent flow cell with an optical path length of 15 micro m for the on-line detection of five neutral analytes. Tight connections between the flow cell and the capillaries were achieved by creating a small O-ring of UV-curing epoxy adhesive on the sharply cut capillary ends. The background electrolyte consisted of 15 mM phosphate buffer at pH 7 and 40 mM sodium dodecyl sulfate (SDS).

On-line fourier transform infrared detection in capillary electrophoresis.

The coupling of Fourier transform infrared (FT-IR) spectroscopy as a new on-line detection principle in capillary electrophoresis (CE) is presented. To overcome the problem of total IR absorption by the fused-silica capillaries that are normally employed in CE separations, a micromachined IR-transparent flow cell was constructed. The cell consists of two IR-transparent CaF2 plates separated by a polymer coating and a titanium layer producing an IR detection window, 150 microm wide and 2 mm long, with a path length of 15 microm.