Analyst Blog

LED-SERDS in Raman Spectroscopy

Raman spectroscopy finds a range of uses in analytical chemistry. Like infra-red (IR) spectroscopy it can provide a vibrational fingerprint by which compounds may be identified. Unlike IR, Raman is a scattering technique that does not require complex sample preparation, and water can be used as a solvent. In some samples, however, the Raman spectrum is rendered useless by intense fluorescence signals.

Chemical engineers Renata Adami (University of Salerno, Italy) and Johannes Kiefer (University of Aberdeen, UK) have developed a new approach to shifted-excitation Raman difference spectroscopy (SERDS) for suppression of fluorescence. SERDS experiments conventionally require expensive diode lasers, but in this Analyst paper Kiefer and Adami demonstrate the use of light-emitting diodes (LEDs) as an inexpensive light source. A dielectric bandpass filter narrows and stabilises the broad LED spectrum to make it usable for SERDS. While the resulting spectral resolution is low, different compounds and functional groups can be clearly distinguished using this method.

To read the full access, please click on the link below. This paper will be free to read for the next three weeks:

Low cost webcam based prism spectrometer

Techniques such as cavity ring-down spectroscopy (CRDS) have greatly enhanced the sensitivity in traditional absorption spectroscopy methods. Although CRDS can detect analytes in very small concentrations in solution, it requires expensive and complex instrumentation, which has restricted its widespread implementation. Alternatively, broadband cavity enhanced absorption spectroscopy (BBCEAS) has emerged to overcome some of these limitations. These adjustments allow for multiplexed data collection and improved resolution.

Researchers at the University of Cambridge, UK,  have constructed a BBCEAS apparatus using relatively simple components and achieved sensitivity levels similar to much more expensive systems.  Using a well-studied process, the Griess Assay, they measured different concentrations of nitrite and the dye Rhodamine 6 G with a system that contained a low cost prism spectrometer and a webcam detector. The limits of detection were found to be 3.7 nM (nitrite) and 850 pM (Rhodamine), and by adding a better detector, these can further be improved upon.

To read the full article, please access the link below. This paper will be free to read for the next three weeks:

High sensitivity liquid phase measurements using broadband cavity enhanced absorption spectroscopy (BBCEAS) featuring a low cost webcam based prism spectrometer
Zhechao Qu, Julia Engstrom, Donald Wong, Meez Islam and   Clemens F. Kaminski
Analyst, 2013,138, 6372-6379
DOI: 10.1039/C3AN01441J