Quantitative Analysis of Nitrate and Nitrite in Water Samples using UV-1900

Significance of the Topic

Accurate monitoring of nitrate and nitrite in water is critical for protecting public health and the environment. Elevated nitrate levels can cause infant methemoglobinemia, while nitrite contamination poses additional risks. Regulatory limits such as the US EPA’s maximum contaminant levels (10 mg/L NO3–N and 1 mg/L NO2–N) underscore the need for reliable analytical methods. The use of UV-VIS spectrophotometry with pre-formulated reagent kits simplifies routine water quality assessments.

Objectives and Study Overview

This study illustrates a quantitative method for determining nitrate-nitrogen and nitrite-nitrogen in bottled, tap and lake water samples. It employs the Shimadzu UV-1900i UV-VIS spectrophotometer in conjunction with the CHEMetrics Vacu-vials test kit, following APHA Standard Methods.

Methodology and Instrumentation

· Sample types: bottled water, tap water and lake water (diluted 1:10).
· Standards: 0.5 ppm NO3–N and NO2–N prepared from 1000 ppm stock.
· Nitrate analysis: reduction with cadmium foil, mixing and 10 min color development.
· Nitrite analysis: direct reaction in Vacu-vial ampoule and 10 min incubation.
· Measurement: absorbance at 520 nm, 1.0 nm slit, 0.1 s integration, LabSolutions UV-Vis advanced formula computes concentration from absorbance using quadratic and cubic equations.

Main Results and Discussion

Standard replicates (n=5) achieved recoveries of 100.6–101.1% and RSD below 1%, confirming precision and accuracy. Environmental samples showed higher nitrate than nitrite levels, reflecting natural oxidation processes. Representative results: bottled water (0.72 ppm NO3–N, 0.03 ppm NO2–N), tap water (1.14 ppm, 0.04 ppm), lake water (1.78 ppm, 0.32 ppm).

Benefits and Practical Applications

· Simplified reagent handling via Vacu-vials reduces preparation time.
· Automated concentration calculations streamline data processing.
· Applicable to routine QA/QC, environmental monitoring and industrial water analysis.

Future Trends and Opportunities

Advancements may include automated sample introduction, miniaturized UV-VIS devices for field deployment and integrated data analytics. Development of multiplexed test kits and AI-enhanced calibration models could further accelerate water quality assessments.

Conclusion

The Shimadzu UV-1900i paired with CHEMetrics Vacu-vials offers a robust, user-friendly approach for quantifying nitrate and nitrite in diverse water matrices. The method delivers regulatory-compliant accuracy and precision while minimizing reagent preparation.

Instrumentation Used

Shimadzu UV-1900i UV-VIS Spectrophotometer: absorbance mode at 520 nm, 1.0 nm slit width, 0.1 s accumulation time.

References

1. McKnight G., Duncan C., Leifert C., Golden M. Dietary nitrate in man: Friend or foe? British Journal of Nutrition 81(5):349–358 (1999)
2. Greer F.R., Shannon M. Infant methemoglobinemia: the role of dietary nitrate in food and water. Pediatrics 116(3):784–786 (2005)
3. APHA Standard Methods for the Examination of Water and Wastewater, Method 4500-NO3–E (2017)
4. APHA Standard Methods for the Examination of Water and Wastewater, Method 4500-NO2–B (2017)
5. National Academy of Sciences. The health effects of nitrate, nitrite and N-nitroso compounds. National Academy Press (1981)