An atomic fluorescence spectrometer for monitoring nitrogen nutrients via NO vapor generation

Long-term and multipoint monitoring is very important to evaluate the safety of water environment. Atomic fluorescence spectrometer (AFS) is generally used for analyzing metals or metalloids in water quality monitoring. In the present work, for the first time, AFS is employed for sensitive monitoring of nitrogen nutrients, i.e., NO₂^-, NO₃^- and NH₄⁺, with nitric oxide (NO) vapor generation. By taking advantage of the different vapor generation conditions for NO₂^-, NO₃^- and NH₄⁺, a unit integrating with sampling, heating, cooling, gas-liquid separation and moisture removal is employed for controlling the vapor generation process, by reacting with either iodide or titanium (III). An antimony hollow cathode lamp is used for the excitation of NO to produce fluorescence emission at 193-320 nm. Linear calibration graphs are obtained within 0.02-2, 0.1-20, 0.2-1 mg L^-1 for NO₂^-, NO₃^- and NH₄⁺, along with detection limits of 0.006, 0.03, 0.06 mg L^-1, respectively. The new analytical strategy obviously broadens the application of AFS, and it is well demonstrated by the determination of NO₂^-, NO₃^- and NH₄⁺ in certified reference materials as well as various real water samples, providing competitive sensitivity with the current techniques for nutrient monitoring in environmental water.