Measurement of TOC in Perfluorochemical (PFOS) Solution

Significance of the Topic

Perfluorooctane sulfonate (PFOS) is a persistent organic pollutant with exceptionally strong carbon–fluorine bonds. Widely used as a surfactant and stain repellent, PFOS resists conventional oxidation methods and accumulates in the environment and wildlife. Accurate total organic carbon (TOC) analysis of PFOS solutions is critical for environmental monitoring and industrial quality control.

Objectives and Overview

This study evaluates and compares two TOC measurement techniques for PFOS quantification: high-temperature catalytic combustion (TOC-LCPH) and wet chemical oxidation (TOC-VWS). The aim is to determine which approach provides reliable, quantitative results for difficult-to-oxidize fluorinated compounds.

Methodology and Instrumentation

Sample Preparation:

• PFOS solutions were prepared in purified water at nominal concentrations of 10 mg/L and 5 mg/L (theoretical carbon concentrations 1.921 mgC/L and 0.961 mgC/L).
• Foaming tendencies of PFOS required use of the TC-IC method to correct for inorganic carbon interference.

Calibration and Measurement:

• Two-point calibration for total carbon (TC) using potassium hydrogen phthalate (0–3 mgC/L).
• Two-point calibration for inorganic carbon (IC) using sodium carbonate/bicarbonate solutions (0–3 mgC/L).

Used Instrumentation

• TOC-LCPH high-temperature catalytic combustion total organic carbon analyzer (680 °C combustion with standard catalyst).
• TOC-VWS wet oxidation total organic carbon analyzer (acid persulfate reagent with UV radiation and heating).

Major Results and Discussion

High-Temperature Catalytic Combustion:

• 10 mg/L PFOS: TOC measured 1.840 mgC/L (theoretical 1.921 mgC/L).
• 5 mg/L PFOS: TOC measured 0.921 mgC/L (theoretical 0.961 mgC/L).

Wet Chemical Oxidation:

• 10 mg/L PFOS: TOC measured 0.008 mgC/L.
• 5 mg/L PFOS: TOC measured 0.014 mgC/L.

The high-temperature combustion method achieved near-quantitative recovery and high sensitivity. In contrast, the wet chemical oxidation approach showed negligible PFOS detection due to its weaker oxidizing power.

Benefits and Practical Applications

• Provides accurate quantification of persistent fluorinated compounds that resist conventional oxidation.
• Supports environmental monitoring and regulatory compliance for PFOS contamination.
• Enables robust quality control in industrial processes where PFOS presence is a concern.

Future Trends and Potential Applications

• Advancement of catalytic materials and reactor designs to further enhance combustion efficiency.
• Integration of TOC analysis with mass spectrometry for compound-specific halogen profiling.
• Development of portable, automated TOC systems for on-site monitoring of persistent organic pollutants.

Conclusion

The TOC-LCPH high-temperature catalytic combustion analyzer delivers superior performance for PFOS measurement compared to wet chemical oxidation, offering accurate and reproducible results essential for both environmental and industrial applications.

Reference

Shimadzu Application News No. O54 "Measurement of TOC in Perfluorochemical (PFOS) Solution", First Edition, June 2015.