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N. Leopold, B. Lendl:
"On-line SERS detection in capillary electrophoresis (CE)";
Poster: Nanospec 2008, Cluj-Napoca; 07.09.2008 - 10.09.2008.

Detection of low analyte concentrations in complex biological, pharmaceutical or environmental samples continues to be a challenge. From the point of view of separation, capillary electrophoresis (CE) may well be the method of choice if the analytes are highly polar or ionic in nature.
CE provides efficient and fast separation, the most common detection method being UV-VIS absorption. Raman spectroscopy could offer a much higher molecular specific content, surface-enhanced Raman scattering (SERS) providing above molecular specific information also high sensitivity.
In this work we present a new on line detection approach for CE by using SERS spectroscopy. A glass connector was inserted between two capillaries (100 µm inner diameter) and used as detection window. A silver substrate, necessary for Raman enhancement, was prepared in situ in the capillary connector by laser induced growth of silver particles [1]. Citrate (10 mM, pH 7) was used as buffer solution and also AgNO3 at 1 mM concentration, necessary for the SERS substrate preparation, was added to the buffer. The Figure shows the evolution in time of the SERS spectra, during the separation process.
In the first minute a highly SERS active substrate is obtained. The SERS spectra of the electrophoretically separated analytes rhodamine 6G (10 ppm) and 4-(2-pyridylazo)resorcinol (6 ppm) are observed at the minutes 2.5 and 4, respectively. Between the analyte SERS spectra only citrate background bands are observed, the detection being not perturbed by memory effects.