3.4. Laboratory and field application
The proposed method was applied to the determination of nitrate in various water samples with a range of salinities and nitrate concentrations. The reliability of the method for analysis of these real samples was checked by recovery experiments and analysis of a certified reference material (Analytical Products Group Inc., Lot Number 40720-40721). Table 4 shows that the recovery of the spiked sample was always in the range of 97–101%, and at the 5% confidence level, there is satisfactory agreement between the result obtained using the proposed method (7.85 ± 0.12 NO3−–N) and certified value (7.69 ± 0.0448 mg/L NO3−–N)