Simultaneous voltammetric determination of nitrites and nitrates in waters

A rapid procedure was developed for the simultaneous voltammetric determination of nitrites and nitrates from a single sample of potable, mineral, or underground water. Nitrites were first determined upon the anodic polarization of a graphite electrode in a sodium sulfate supporting electrolyte. Next, ascorbic acid and a copper salt were added, and the solution was acidified to an optimum pH value. A copper electrode was formed in situ, and the nitrate signal was recorded as the first derivative using cathodic sweep. The procedure does not require sample preparation or oxygen removal from the solution with a nitrogen flow. The copper-graphite electrode was regenerated electrochemically in the same solution. The analytical range for nitrite ions was 0.2-10.0 mg/L in the presence of any amount of nitrates. Nitrates were quantitatively determined in the range 0.5-5 mg/L. Common cations and anions in waters did not interfere with the determination. The procedure is suitable for the analysis of potable, mineral, underground, and surface waters. The procedure was verified by the added-found method and by the photometric procedure GOST (State Standard) 18826-73.