No abstract

A chemiluminescence system is described for the determination of nitrite ion based on new designs for an ozone generator, liquid-gas separator and chemiluminescence reaction cell. The method is based on the gas-phase chemiluminescence reaction between ozone and nitric oxide, which is generated from the reduction of nitrite with iodide in sulfuric acid solution. The efficiency of the system was evaluated by investigation of the analytical performance characteristics of the system for nitrite determination in batch and flow injection procedures. Under optimal conditions, the chemiluminescence response of the system was linear against the nitrite concentration over the range 1 to 1 × 10 4 ng ml -1 in the batch procedure and 10 to 5 × 10 3 ng ml -1 in the flow injection procedure, with detection limits of 1 and 10 ng ml -1 , respectively. The method is highly selective and allows for the determination of nitrite in the presence of high concentrations of several cationic, anionic and nitrogen containing species. It has been successfully applied to the analysis of nitrite in natural water and soil extracts.

A simple flow injection spectrophotometric method for the determination of nitrite is described. Nitrite injected into the flow system reacts with thiourea in acidic medium and the generated thiocyanate ion reacts with Fe(III) in the reagent solution to produce a highly colored product. The influences of chemical and physical parameters including reagent concentrations, sample volume injected, flow rates of the carrier and reagent solutions, reaction coil length and reaction temperature, were studied and optimum values of these parameters were established. Under the optimum conditions, the calibration curve for nitrite was linear over the concentration range 0.36 -90 µg ml -1 without preconcentration and over the range 3.8 -500 ng ml -1 with a simple online preconcentration step using an anion exchange column. The corresponding detection limits were 0.36 µg ml -1 and 3.8 ng ml -1 , respectively. Up to 25 samples can be analyzed per hour, with an average relative standard deviation of ≤ 1.2%. Interferences by various foreign ions were studied and the method was applied to the determination of nitrite in water and spiked water samples.