Dynamic end-point total organic fluoride measurement

A device for dynamic end-point total organic fluoride measurement of a PFAS-containing sample, the device comprising:

• a non-oxidation cell;
• an oxidation cell comprising a boron-doped diamond electrode;
• a fluoride ion-selective electrode configured to measure fluoride concentration in the sample;
• a recirculation system for moving the sample between the oxidation cell and the non-oxidation cell;
• and
• a processor configured to:
• control application of electrical potential to the BDD electrode;
• receive a time-dependent fluoride measurement signal from the ISE;
• compute at least the second derivative (d²F/dt²) of the fluoride measurement signal;
• and
• determine a dynamic oxidation end-point when the second derivative indicates depletion of oxidizable C-F bonds, characterized by a change in curvature or transition of the second derivative from positive to negative.

A method for measuring total organic fluoride of a PFAS containing sample, comprising:

• placing a sample comprising a PFAS compound in a measurement device, wherein the measurement device comprises an oxidation cell comprising a boron-doped diamond (BDD) electrode and a non-oxidation cell;
• measuring, using the measurement device, an amount of total inorganic fluoride in the sample before oxidation;
• applying an electrical potential to a portion of the sample in the oxidation cell, wherein the electrical potential oxidizes the PFAS compound and generates fluoride ions;
• measuring, using the measurement device, a fluoride signal over time during or after the oxidation to provide a measurement signal of total organic fluoride;
• and
• determining a dynamic endpoint of the oxidation using a model-based prediction that depends on the rate of fluoride production, wherein the model-based prediction comprises at least one of:
• exponential decay fitting, piecewise linear regression, or kinetic model fitting of the fluoride generation curve.