Deep-UV Raman spectroscopy is a promising method for the analysis of nitrates and nitrites in water at ppm (mg/l) concentrations. In addition to the high sensitivity, the tunability of the laser source allows to deeper investigate the photoinduced reactions taking place under deep-UV illumination. Under these conditions, nitrate ions decompose into oxygen and nitrite through different reaction pathways. Analysis of the evolution of nitrate and nitrite Raman modes as a function of the excitation wavelength allows for estimating the photo-energy dependent quantum yield of the photolysis process. The results highlight the limits and capabilities of deep UV Raman as a on-line nitrate and nitrite monitoring method.

Short-wavelength (λ < 260 nm) Raman spectroscopy offers an advantage of a generally higher sensitivity than Raman spectroscopy in the visible range. An application with high potential is its use for environmental water analysis targeting archetypal compounds that are present in industrial and urban sewage water. However, this application is feasible only if specific performance benchmarks are met. We validate the applicability of a simple and cost-effective deep-UV Raman spectrometer (λ exc = 236.5 nm). The analysis brings to the fore that the experimentally derived detection limits the studied archetypal compounds are to high by several orders of magnitude. We outline potential further development and associated limitations. These are the deterioration of the analysed species by photolysis as a consequence of the high photon energy and intensity, and the self absorption of the UV radiation. These effects are explained and partially corrected along a simple mathematical model from which a general limit of detection is estimated.