The role of Raman spectroscopy in the analytical chemistry of potable water

Advances in instrumentation are making Raman spectroscopy the tool of choice for an increasing number of chemical applications. For example, many recalcitrant industrial process monitoring problems have been solved in recent years with in-line Raman spectrometers. Raman is attractive for these applications for many reasons, including remote non-invasive sampling, minimal sample preparation and tolerance of water. To a lesser extent, Raman spectroscopy is beginning to play a significant role in environmental analysis for the same reasons. At present, the environmental applications typically apply only to the most contaminated situations due to the still relatively high limits of detection. However, some emerging sampling technologies hold out the promise that Raman may soon be more widely applicable to the analytical chemistry of potable water. Herein we discuss these recent advances, summarize some examples of environmental applications to aqueous systems and suggest avenues of future developments that we expect to be most useful for potable water analysis. Also, a simplified, but detailed, theory of normal Raman scattering is presented. While resonance-enhanced Raman spectroscopy, surface-enhanced Raman spectroscopy and non-linear Raman techniques are briefly discussed, their theories and instrumental configurations are not addressed. Also, this article deals primarily with the modern dispersive Raman experiment (as opposed to the Fourier transform Raman experiment), because it seems most suited for potable water analysis. The goal of this article is to give the environmental scientist with no specialized knowledge of the topic just enough theory and background to evaluate the utility of this rapidly developing analytical tool.