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The goal of this study is to develop Surface-enhanced Raman scattering (SERS) detection
methods for flow injection analysis (FIA) and high performance liquid chromatography (HPLC).
Nucleic acid bases have been chosen for analysis because of their importance in life processes. The
advantages to the use of SERS-based detection include its sensitivity, specificity and versatility.
With the development of improved methodology, the detection limits should be comparable to UV
spectroscopy. However, the specificity is considerably superior to that obtained with electronic
spectroscopy in that the Raman spectrum provides a molecular fingerprint of the individual
analytes. Raman spectroscopy is very versatile: aqueous samples, gases and solids can be analyzed
with equal facility.
The results presented here demonstrate that SERS can be used as a detection method for both
FIA and HPLC detection. In the following experiments Ag sols have been used as the active
substrate. The effect of various parameters such as temperature, pH, flow rate, and the nature of
the interface between the HPLC system and the Raman spectrometer have been examined. One
of the most significant findings is that the temperature of the Ag sol/HPLC effluent mixture has
a dramatic effect on the SERS intensities. This effect is a result of increased colloid aggregation
at higher temperatures. Aggregation is known to produce greater enhancement in SERS and
proceeds much more rapidly at elevated temperatures. An increase in the temperature of the Ag
sol enables SERS detection under flowing conditions and in real time. This is a substantial
improvement over many of the previous attempts to interface SERS detection to FIA or HPLC.
In most of the previous studies, it was necessary to stop the flow as the analyte eluted from the
chromatogram and measure the SERS spectra under static conditions.
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