SPADNS Colorimetric Method to Quantify Fluorides in Water

Importance of the Topic

Fluoride concentration in drinking water is critical to dental health and public safety. While low levels of fluoride prevent tooth decay, excessive exposure can lead to fluorosis and other health concerns. Reliable quantification using the SPADNS colorimetric method supports regulatory compliance and environmental monitoring.

Objectives and Study Overview

This application note demonstrates the use of the Agilent Cary 60 UV-Vis spectrophotometer and Cary WinUV software concentration module to quantify fluoride in water. The goal is to streamline absorbance measurements, automate calibration and data analysis, and validate performance across the 0–1.4 mg/L analytical range.

Methodology and Instrumentation

• Instrumentation: Agilent Cary 60 UV-Vis spectrophotometer with 10 mm quartz cell; Cary WinUV software version 5.1.3 concentration module for data acquisition and analysis.
• Reagents: Zirconyl-SPADNS reagent prepared by mixing ZrCl2·8H2O and SPADNS dye in acidic medium; stock fluoride solution (100 mg/L) and calibration standards (0.2–1.4 mg/L) in polyethylene containers to avoid glass attack.
• Procedure: Zero the instrument with reference solution; measure absorbance at 570 nm in triplicate; generate calibration curve with linear fit (minimum R² 0.95000); apply method to unknown samples.

Main Results and Discussion

A linear calibration curve with slope –0.1872 and R² 0.9993 was obtained for 0–1.4 mg/L fluoride. Analysis of spiked samples (0.5 and 0.7 mg/L) yielded recoveries within acceptable limits and low relative standard deviations. The software automatically generated concentration reports, reducing manual data handling and accelerating throughput. Water samples free from interfering ions were successfully analyzed following standard pretreatment to remove chlorine and other contaminants.

Benefits and Practical Applications of the Method

This approach offers rapid setup, automated data processing, and high analytical accuracy. It meets drinking water guidelines (0.5–1.5 mg/L) and allows extension to 3.5 mg/L via quadratic calibration. Reusable method templates ensure consistency across multiple analyses and laboratories.

Future Trends and Possibilities

Advances may include in-line or on-site monitoring with flow injection analysis, enhanced software for kinetic and multicomponent assays, and cloud-based data integration for remote surveillance and regulatory reporting. Integration with laboratory information management systems will further streamline quality assurance workflows.

Conclusion

The Agilent Cary 60 UV-Vis spectrophotometer combined with Cary WinUV software enables precise, efficient quantification of fluoride in water using the SPADNS colorimetric method. Automated calibration and reporting enhance productivity and support reliable public health monitoring.

References

1. World Health Organization. Guidelines for Drinking-Water Quality, 4th Edition, 2011.
2. Shahroom, N. B.; Mani, G.; Ramakrishnan, M. Interventions in Management of Dental Fluorosis, J. Family Med. Prim. Care 2019, 8(10), 3108.
3. American Public Health Association. Standard Methods for the Examination of Water and Wastewater, Method 4500-F D, 22nd Edition.