Granted Patent B2

US 12,693,261 · App. 17/951,777 · Granted Jul 28, 2026

Inventors: Vishnu Vardhanan Rajasekharan (Fort Collins, CO); Matthew Ryan Salzer (Loveland, CO); Russell Young (Fort Collins, CO); Benjamin James Walter (Fort Collins, CO); Jorge Gomez (Fort Collins, CO)

Assignee: Hach Company

G01N27/4163G01N27/308

Abstract

Claims (32)

1 . A method for measuring an amount of total organic fluoride of a polyfluoroalkyl substance (PFAS) compound in a sample, comprising:

placing the sample comprising the PFAS compound in a measurement device, wherein the measurement device comprises an oxidation cell and a non-oxidation cell, wherein the oxidation cell comprises a boron-doped diamond electrode;

measuring, using the measurement device, an amount of total inorganic fluoride of the sample before an oxidation;

applying an electrical potential to a portion of the sample in the oxidation cell, wherein the electrical potential oxidizes the PFAS compound;

measuring, using the measurement device, the amount of total organic fluoride of the sample after the oxidation to provide a measurement signal of the total organic fluoride;

determining a first derivative of the measurement signal of the total organic fluoride; and

comparing the first derivative to a predetermined value, wherein if the first derivative is greater than the predetermined value then adjusting the electrical potential provided to the oxidation cell.

2 . The method of claim 1 , wherein the sample circulates between the oxidation cell and the non-oxidation cell.

3 . The method of claim 1 , wherein the electric potential provides a step wise electrochemical oxidation.

4 . The method of claim 1 , further comprising determining a second derivative of the measurement signal of the total organic fluoride.

5 . The method of claim 1 , further comprising periodically turning off the electrical potential to the oxidation cell for a temperature stabilization.

6 . The method of claim 1 , further comprising periodically turning off the electrical potential to the oxidation cell to reduce an electrical noise as measured by the measurement device.

7 . The method of claim 1 , further comprising shielding the measurement device from the electrical potential applied during the oxidation.

8 . The method of claim 1 , further comprising filtering the first derivative to reduce electrical noise.

9 . The method of claim 1 , wherein the oxidation generates fluoride from a digestion of the PFAS compound using the boron-doped diamond electrode.

10 . The method of claim 1 , wherein the first derivative approaches an asymptote representing a linear background of the measurement device.

11 . The method of claim 1 , wherein the first derivative approaching an asymptote defines a dynamic end point of the oxidation.

12 . The method of claim 1 , wherein a total fluoride content equals a summation of the total inorganic fluoride and the total organic fluoride.

13 . The method of claim 1 , wherein a duration of the oxidation is determined by the first derivative reaching a threshold value.

14 . The method of claim 1 , further comprising subtracting a linear background from the measurement of the total inorganic fluoride and from the measurement of the total organic fluoride.

15 . The method of claim 14 , wherein the linear background comprises system contribution variables, wherein the system contribution variables are selected from the group consisting of: a rate constant of oxidation at the surface of the boron-doped diamond electrode, a penetration depth and diffusional rate of hydroxyl radicals, a total volume of the oxidation cell, and an exchange rate of the sample between the oxidation cell and the non-oxidation cell.

16 . The method of claim 1 , wherein the measurement device is selected from the group consisting of: an electrochemical device and an optical device.

17 . A device for measuring an amount of total organic fluoride of a PFAS compound in a sample, comprising:

a non-oxidation cell;

an oxidation cell comprising an ion selective electrode and a boron-doped diamond electrode; and

a processor;

wherein the processor is configured to:

measure an amount of total inorganic fluoride of the sample before an oxidation;

apply an electrical potential to a portion of the sample in the oxidation cell, wherein the electrical potential oxidizes the PFAS compound;

measure the amount of total organic fluoride of the sample after the oxidation to provide a measurement signal of the total organic fluoride;

determine a first derivative of the measurement signal of the total organic fluoride; and

compare the first derivative to a predetermined value, wherein if the first derivative is greater than the predetermined value then adjusting the electrical potential provided to the oxidation cell.

Assignments (1)

Continuity (1)

References Cited (18)