On-Column Surface-Enhanced Raman Spectroscopy Detection in Capillary Electrophoresis Using Running Buffers Containing Silver Colloidal Solutions

• Published in: Analytical chemistry (Washington) Vol. 72; no. 8; pp. 1866 - 1871
• Main Authors: Nirode, William F, Devault, Gerald L, Sepaniak, Michael J, Cole, Roderic O
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 15.04.2000
• Subjects: Analytical chemistry; Chemistry; Chromatographic methods and physical methods associated with chromatography; Exact sciences and technology; Other chromatographic methods; Scientific imaging; Silver; Chemical analysis; Zone electrophoresis; Capillary electrophoresis; Coupled method; Vitamin; Riboflavin; Transition metal; Metal particle; Silver; Multicomponent analysis; Sample preparation; Surface Enhanced Raman Spectrometry; Qualitative analysis; Xanthene dye; Aqueous dispersion; Colloid particle
• ISSN: 0003-2700; 1520-6882
• DOI: 10.1021/ac991248d

Direct on-column surface-enhanced Raman spectroscopy (SERS) detection is demonstrated in capillary electrophoresis (CE). Distinctive SERS spectra of two test compounds, riboflavin and Rhodamine 6G, are obtained in 100 μm i.d. fused-silica capillaries under CE conditions using running buffers that contain silver colloidal solutions. Detection is performed using an unmodified commercial Raman spectrometer in a confocal microscope mode of operation. The effects of laser power, wavelength, spectra acquisition time, silver colloidal concentration, and applied voltage (i.e., flow rate) on the quality of SERS spectra are evaluated. Using laser powers of 17 mW (at the sample) at 515 nm and employing 1 s spectral acquisition times, spectra with bands exhibiting signal-to-noise ratios greater than 10 could be obtained for 1.0 × 10-6 M riboflavin and very low nanomolar concentrations of Rhodamine 6G. This was accomplished without optimization of silver colloidal solution compositions and by using a low-throughput spectrometer. Incorporation of the colloidal solutions into running buffers is shown to have little effect on the separation of the test compounds as monitored using a laser-induced fluorescence instrumental scheme. However, SERS spectra degrade if the capillary is not rinsed between experiments. Riboflavin and Rhodamine 6G spectra are obtained on-the-fly for actual CE separations. In the case of the latter solute, the injected quantity was approximately 90 amol.