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Analytical Chemistry

Polymer Beads Improve Detection Limits Of Absorption Spectroscopy

Polystyrene beads suspended in samples increase optical path length and sample sensitivity

by Celia Henry Arnaud
January 12, 2015 | A version of this story appeared in Volume 93, Issue 2

In absorption spectroscopy, absorbance is directly proportional to the path length of the light through a sample containing analytes. In a new method called multiscattering-enhanced absorption spectroscopy, Christian Santschi, Volodymyr B. Koman, and Olivier J. F. Martin of ETH Lausanne report a low-cost, quick, and easy way to increase the path length through samples and thus improve the sensitivity of standard absorption spectroscopy. No instrument adaptations are required: The sample itself is modified (Anal. Chem. 2014, DOI: 10.1021/ac502267q). The researchers suspend polystyrene beads, which do not absorb visible light, in a cuvette with a sample containing the analytes. Light scattered by the beads traverses a longer path length that depends on the beads’ size and concentration. The researchers demonstrate that the method improves detection limits for various analytes, including 10-nm gold nanoparticles and some organic compounds, by a factor of roughly three to seven, respectively. The method is particularly well-suited to low analyte concentrations.

Diagram shows standard sample preparations (black arrows/spectrum) compared with adding light-scattering beads in absorption spectroscopy (red arrows/spectrum).
Compared with standard sample preparations (black arrows/spectrum), adding light-scattering beads increases the optical path length and analyte sensitivity in absorption spectroscopy (red arrows/spectrum).


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