Nirode WF, Devault GL, Sepaniak MJ, Cole RO
Department of Chemistry, University of Tennessee, Knoxville 37996-1600, USA.
Anal Chem. 2000 Apr 15;72(8):1866-71. 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 microm 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 x 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.
在毛细管电泳（CE）中实现了直接柱上表面增强拉曼光谱（SERS）检测。在内径为100微米的熔融石英毛细管中，使用含有银胶体溶液的运行缓冲液，在CE条件下获得了两种测试化合物核黄素和罗丹明6G的独特SERS光谱。使用未改性的商用拉曼光谱仪在共聚焦显微镜操作模式下进行检测。评估了激光功率、波长、光谱采集时间、银胶体浓度和施加电压（即流速）对SERS光谱质量的影响。在515nm处使用17mW（在样品处）的激光功率并采用1s的光谱采集时间，对于1.0×10⁻⁶M的核黄素和极低纳摩尔浓度的罗丹明6G，可以获得带的信噪比大于10的光谱。这是在未优化银胶体溶液组成的情况下，通过使用低通量光谱仪实现的。将胶体溶液加入运行缓冲液中，如使用激光诱导荧光仪器方案监测的那样，对测试化合物的分离影响很小。然而，如果在实验之间不冲洗毛细管，SERS光谱会退化。对于实际的CE分离，可以实时获得核黄素和罗丹明6G的光谱。对于后一种溶质，进样量约为90 amol。
