Nitrate Analysis of Water Using a Fiber Optics Dip Probe

Importance of the Topic

Nitrate contamination in water presents significant environmental and health challenges. Rapid and accurate determination of nitrate levels supports regulatory compliance, safeguards drinking water quality, and protects aquatic ecosystems.

Study Objectives and Overview

This application note evaluates the use of a quartz fiber optics dip probe on a Cary 50 or Cary 60 UV-Vis spectrophotometer for the quantification of nitrate in water. The goal is to demonstrate the method s precision, speed, and suitability for both laboratory and field measurements.

Methodology and Instrumentation

• Spectrophotometer Cary 50 UV-Vis or Cary 60 UV-Vis
• Fiber optics assembly including dip probe and coupler
• Software Cary WinUV concentration application
• Reagents Potassium nitrate standards hydrochloric acid chloroform deionized water

Standards in the range of 0 to 7 mg NO3 N per liter were prepared according to standard methods. Absorbance readings were taken at 220 nm and 275 nm. Organic matter interference was corrected by subtracting twice the 275 nm absorbance from the 220 nm absorbance. Six calibration standards each run in triplicate provided data for curve fitting.

Main Results and Discussion

A quadratic calibration curve produced a correlation coefficient of 0.99931, indicating excellent linearity across the tested range. Relative standard deviations for standards and two tap water samples were below 1.8 percent. A brief rinse in distilled water between measurements prevented carryover. Twenty four measurements including replicates were completed in approximately five minutes.

Benefits and Practical Applications

• High precision with RSD below 2 percent
• Fast throughput allowing dozens of measurements in minutes
• Versatile deployment for laboratory or field use
• Reduced use of cuvettes and disposable materials

Future Trends and Potential Uses

Integration of fiber optic probes with portable or handheld UV-Vis instruments could enable real time field monitoring. Automated probe washing and sample handling can further increase throughput. Adaptation to additional analytes through wavelength selection expands application scope.

Conclusion

The quartz fiber optics dip probe on Cary 50 or Cary 60 UV-Vis instruments offers a reliable, rapid, and precise approach for routine nitrate analysis in water. Its ease of use and high sample throughput make it an attractive alternative to traditional cuvette methods in both lab and field environments.

Reference

• D Eaton L S Clesceri and A E Greenberg Standard Methods for the Examination of Water and Wastewater 19th Edition American Public Health Association Washington 1995 p4-85
• P A Liberatore Automated nitrate analysis of water Agilent publication UV59