Dynamic endpoint total organic fluoride measurement

Abstract

One embodiment provides a method for measuring the amount of total organic fluoride content of a PFAS-containing sample, the method comprising: placing a sample comprising a PFAS compound into a measurement device, where the measurement device comprises an oxidation pond and a non-oxidation pond, where the oxidation pond comprises a boron-doped diamond electrode; measuring the amount of total inorganic fluoride of the sample prior to oxidation using the measuring device; applying an electric potential to a portion of the sample in the oxidation pond, wherein the electric potential oxidizes the PFAS compound; measuring an amount of total organic fluoride of the sample after the oxidation using the measuring device to provide a measurement signal of the total organic fluoride; and determining a first derivative of the measurement signal of the total organic fluoride. Other aspects are described and claimed.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to U.S. patent application serial number 17 / 951,777, filed on September 23, 2022, entitled “Dynamic Endpoint Total Organic Fluoride Measurement,” the contents of which are incorporated herein by reference. Technical Field

[0002] The present application relates generally to the measurement of total organic and inorganic fluorides in a sample, and more particularly to the measurement of total organic and inorganic fluorides in a sample using a boron doped diamond oxidation cell and a fluoride ion selective electrode. Background Art

[0003] Ensuring water quality is critical in a variety of industries such as drinking water, wastewater treatment and reuse, pharmaceuticals, and other manufacturing fields. In addition, ensuring water quality is critical to the health and well-being of humans, animals, and plants that depend on water for survival. Per- and polyfluoroalkyl substances (PFAS) are a large class of synthetic chemicals that affect public health at ultra-low levels. Governments and regulatory agencies have set limits on PFAS concentrations. Such limits can be set for PFAS compounds in surface water, groundwater, wastewater, biosolids, and soil. Several industries that use or have used PFOS / PFOA are replacing them with alkyl fluoride alternatives, which remain a concern. Summary of the invention

[0004] In summary, one embodiment provides a method for measuring the amount of total organic fluoride content in a PFAS-containing sample, the method comprising: placing a sample containing PFAS compounds in a measuring device, wherein the measuring device comprises an oxidation pool and a non-oxidation pool, wherein the oxidation pool comprises a boron-doped diamond electrode; using the measuring device to measure the amount of total inorganic fluoride in the sample before oxidation; applying an electric potential to a portion of the sample in the oxidation pool, wherein the electric potential oxidizes the PFAS compounds; using the measuring device to measure the amount of total organic fluoride in the sample after the oxidation to provide a measurement signal of the total organic fluoride; and determining the first derivative of the measurement signal of the total organic fluoride.

[0005] Another embodiment provides a method for measuring the amount of an analyte in a sample, the method comprising: placing the sample in a measuring device, wherein the measuring device comprises an oxidation pool and a non-oxidation pool, wherein the oxidation pool comprises a boron-doped diamond electrode; using the measuring device to measure the amount of a first component of the sample before oxidation, wherein an ion-selective electrode measures the first component; applying an electric potential to a portion of the sample in the oxidation pool, wherein the electric potential oxidizes the sample; and using the measuring device to measure the amount of a second component of the sample after the oxidation, wherein another ion-selective electrode measures the second component.

[0006] Another embodiment provides a device for measuring the amount of total organic fluoride content of PFAS compounds in a sample, the device comprising: a non-oxidizing pool; an oxidizing pool comprising an ion-selective electrode and a boron-doped diamond electrode; a processor; the device for measuring the amount of fluoride content of PFAS compounds in a sample is configured to: use the measuring device to measure the amount of total inorganic fluoride of the sample before oxidation; apply an electric potential to a portion of the sample in the oxidizing pool, wherein the electric potential oxidizes the PFAS compound; use the measuring device to measure the amount of total organic fluoride of the sample after the oxidation to provide a measurement signal of the total organic fluoride; and determine the first derivative of the measurement signal of the total organic fluoride.

[0007] The foregoing is a summary and thus may contain simplifications, generalizations, and omissions of detail; consequently, those skilled in the art will appreciate that this summary is illustrative only and is not intended to be in any way limiting.

[0008] For a better understanding of the embodiments, together with other and further features and advantages thereof, reference is made to the following description taken in conjunction with the accompanying drawings.The scope of the invention will be indicated in the appended claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 A flow chart for dynamic endpoint detection is shown.

[0010] Figure 2 An exemplary stabilization module for a fluoride ion selective electrode in a recirculation path is shown.

[0011] Figure 3A Exemplary data for dynamic endpoint detection of PFOA in the presence of inorganic fluoride are shown.

[0012] Figure 3B Exemplary data for the first derivative of endpoint detection of PFOA are shown.

[0013] Figure 4AExemplary data of PFOA oxidation curves are shown.

[0014] Figure 4B Exemplary data from a PFOA oxidation profile of a portion of the equilibration step are shown.

[0015] Figure 5A Exemplary data of a PFOA kinetic oxidation profile for kinetic endpoint detection are shown.

[0016] Figure 5B Exemplary data for a calibration curve of PFOA for kinetic endpoint detection are shown.

[0017] Figure 6 An example of a computer circuit system is shown. DETAILED DESCRIPTION

[0018] It will be readily understood that, in addition to the exemplary embodiments described, the components of the embodiments generally described and illustrated in the drawings herein may be arranged and designed in a variety of different configurations. Therefore, the following more detailed description of the exemplary embodiments as shown in the drawings is not intended to limit the scope of the embodiments, but merely represents exemplary embodiments.

[0019] References throughout this specification to "one embodiment" or "an embodiment" (etc.) mean that a particular feature, structure, or characteristic described with respect to that embodiment is included in at least one embodiment. Thus, the appearances of the phrases "in one embodiment" or "in an embodiment", etc., at various locations throughout this specification do not necessarily all refer to the same embodiment.

[0020] In addition, the described features, structures or characteristics can be combined in any suitable manner in one or more embodiments. In the following description, many specific details are provided to give a comprehensive understanding of the embodiments. However, those skilled in the relevant art will recognize that various embodiments can be implemented without one or more specific details, or implemented using other methods, components, materials, etc. In other cases, well-known structures, materials or operations are not shown or described in detail. The following description is only for illustration, and only some exemplary embodiments are described.

[0021] Per- and polyfluoroalkyl substances (PFAS) are a large class of synthetic chemicals that affect public health at ultra-low levels, even in the parts per trillion (ppt) range. The current U.S. Environmental Protection Agency (EPA) Health Advisory Committee states a maximum value of 70 ng / L for PFOS and PFOA in drinking water, and recommends 1 µg / L of total organic fluoride (TOF) as an alternative measurement for fluorinated compounds in surface water, groundwater, wastewater, biosolids, and soil. Other governments have imposed regulatory limits on PFAS compounds. Treatment plants make significant investments to meet these limits. Many of these treatment methods have not been fully validated. Several industries that use PFOS / PFOA are replacing them with alkyl fluoride alternatives, and these replacements still have health and environmental concerns. Very few high-end laboratory methods have agency approval for PFAS analysis. The technology to analyze PFAS in field environments does not exist. In many cases, field analysis of these parameters is impractical due to the complex sample preparation required in existing methods.

[0022] There are many challenges with TOF measurements, which can be critical for the detection of per- and polyfluoroalkyl substances. For example, methods and systems require ultra-low level detection of a wide variety of compounds. PFAS compounds are widely present in the environment. The difficulty in degrading larger molecules into smaller molecules that are difficult to degrade, precursor conversion, chemical structure changes after industrial discharges or during the leaching process in landfills, and high background during TOF analysis because most tap water has a 0.5 to 1 ppm background of inorganic fluoride anions from municipal treatment. In addition, there are a variety of locations and conditions to be tested, such as military bases, airports, industrial plants, landfills, fire training grounds, etc. Some tests only measure a limited set of chemicals and precursors and cannot identify all PFAS compounds.

[0023] Specifically, some methods for detecting PFAS compounds have limitations. For example, combustion ion chromatography may have inefficient adsorption of organic and inorganic fluoride activated carbon. The method may have an additional step of eluting inorganic fluoride from activated carbon by washing with a neutral nitrate solution. There is still a complex process of burning activated carbon loaded with adsorbable organic fluoride (AOF) in an oxygen stream under thermal hydrolysis conditions. This may produce toxic gas byproducts of activated carbon after combustion captured in the absorption medium, wherein corrosive hydrogen fluoride is formed during the combustion process. The corrosive hydrogen fluoride is then condensed back into the solution, and the hydrogen fluoride dissociates to form fluoride anions. A separate aliquot of the absorption solution containing fluoride anions of known volume is then injected into the inherently complex ion chromatograph through a sample injection valve. This requires a long cycle time to separate the halogen anions on the anion separation column of the ion chromatograph (IC). In addition, before measuring the IC conductivity detector of fluoride, an anion suppression device is required to reduce the conductivity of the eluent.

[0024] What is needed is an accurate and simpler TOF measurement method for PFAS analysis. For example, it is advantageous to eliminate the combustion cartridge to avoid the generation of hydrogen fluoride gas in conventional TOF, as well as the generation of oxidants without the use of reagents during the digestion process. On boron-doped diamond (BDD) electrodes, hydroxyl radical generation is more efficient because there is a weak interaction between the radicals and BDD. The robustness of BDD can provide long-term stability under harsh conditions, high current density, fluctuating pH, and complex solution matrices. Bipolar electrode configurations can be used to improve the oxidation efficiency of PFAS. Treatment effectiveness verification can be achieved through the total organic fluoride and total oxidizable precursor measurements. This can be achieved by digesting PFAS on BDD electrodes and detecting fluoride electrochemically or optically.

[0025] Therefore, the systems and methods described herein provide a technique for measuring PFAS and other substances in a sample. In one embodiment, total organic and inorganic fluorides can be determined in the most efficient way. The sample solution can be recycled through a boron-doped diamond (BDD) oxidation cell and a fluoride ion selective electrode (ISE). The flow rate, volume, stirring and temperature stabilization module can be measured and optimized to achieve the best performance of the ISE under oxidation process conditions. Fluoride content can be measured during the oxidation of PFAS in a recycling cell. Oxidation can be operated in a stepwise or continuous mode. Appropriate shielding techniques can be used during the continuous oxidation mode to ensure that the ISE signal is not distorted due to the higher voltage / current applied to the BDD electrode. During the stepwise oxidation implementation, an ISE electrode is used between the oxidation steps. Fluoride generation can be monitored during the equilibrium time between the oxidation steps. The signal measured by the ISE electrode can then be processed using first-order and / or second-order derivative analysis to determine the dynamic endpoint. The oxidation curve is usually composed of exponential oxidation. The endpoint can be determined when the curvature becomes less obvious. When the first-order and / or second-order derivative is below a predetermined limit, the endpoint can be determined. The first derivative analysis may show a higher signal and then asymptote to the background slope at the end. Noise may be amplified during the first and second derivative analysis. In one embodiment, appropriate data filtering is required to achieve the best quality signal. Fluoride can be detected before, during and after oxidation. The fluoride content measured before oxidation can provide the total inorganic fluoride. Once oxidation begins, the fluoride content can increase exponentially due to the degradation of PFAS. It can then reach a stable value, and the difference between the initial fluoride measurement and the final fluoride value provides the total organic fluoride content. The total amount of TOF and total inorganic fluoride (TIF) provides the total fluoride value.

[0026] The illustrated exemplary embodiments will be best understood by referring to the accompanying drawings.The following description is for illustration only and describes only certain exemplary embodiments.

[0027] In one embodiment, the method and apparatus can measure the total organic fluoride in a sample. The sample can be drinking water, industrial wastewater, from a natural water body, and the like. In one embodiment, a boron-doped diamond (BDD) electrode can oxidize PFAS compounds to produce fluoride. Fluoride can be measured using an ion selective electrode (ISE) or other non-invasive techniques such as x-ray photoelectron spectroscopy. In one embodiment, fluoride production during oxidation of PFAS can be measured. The system can monitor in situ fluoride production during oxidation in a BDD electrochemical (Echem) cell.

[0028] In one embodiment, fluoride production from oxidation can start quickly, for example, exponentially. Over time, fluoride production begins to stabilize or stabilize to an asymptote. In one embodiment, the first and second derivatives can be calculated from the slope of fluoride production. In one embodiment, the end point of oxidation can be determined dynamically. For example, when the PFAS concentration is low or the sample contains easily oxidizable compounds, the time required for complete oxidation can be less, and when the PFAS concentration is high or the sample contains more difficult to oxidize compounds, the time required for complete oxidation can be longer. In this way, the oxidation time can be optimized for time so that the oxidation time is dynamically optimized for PFAS concentration. As an example, in a sample with a low PFAS concentration, oxidation and waiting for a long time to measure may not be required. As another example, some PFAS compounds require longer oxidation even at low concentrations. The methods described herein can optimize the time for oxidation for PFAS compounds and / or concentrations. Using a fixed oxidation time may not oxidize PFAS compounds, or may last too long. Using kinetic endpoint detection utilizing first and second derivatives, the method can ensure that oxidation is complete for all PFAS compounds including complex PFAS molecules.

[0029] In one embodiment, measuring the fluoride produced by oxidation can provide a feedback loop for the Echem generator of the system. Feedback can increase or decrease the voltage or current of the Echem cell according to the fluoride generation / production curve. In other words, the energy use in the system and method can be optimized. In one embodiment, when reaching an asymptote, a small slope can be maintained. This small slope can measure the background contribution from the cell components or other components that contribute to the fluoride signal. In one embodiment, the method and apparatus can measure pH or carbon dioxide.

[0030] In one embodiment, the measurement can be continuous or stepwise. Stepwise can allow for more accurate measurements because the sample can reach homogeneity within the cell or enable the Echem cell to be reset. In continuous measurements, the potential applied for oxidation may have an effect on the electrochemical measurement, which should be compensated by filtering or shielding techniques.

[0031] Reference Figure 1, in one embodiment, a flow chart of a dynamic endpoint detection is shown. In one embodiment, a set voltage or potential can be used as a starting point. PFAS compounds can be oxidized in a digestion tank. Samples or standard solutions can be recycled during the digestion process. In other words, mixing or flow can be generated in the digestion tank. Recirculation can move the fluid sample between the oxidation tank and the non-oxidation tank. The non-oxidation tank may not contain irritating reagents, such as hydroxyl radicals or other oxidants. The amount of fluoride can be measured in the non-oxidation tank. The measurement can be a continuous measurement. The measurement can also determine the first and second derivatives of the fluoride measurement signal. Determining the first and second derivatives of the fluoride measurement signal may generate noise. The noise can be electrical noise. Noise can be filtered using a noise filter, which can be a hardware or software component of the measurement system. In one embodiment, after noise filtering, the fluoride measurement signal can be compared with a predetermined threshold. If the signal is lower than or equal to the predetermined threshold, the system can proceed to the next step. If the signal is not less than or equal to the predetermined threshold, the method and system can continue with the step-wise continuous electrochemical oxidation of PFAS using the BDD electrode in the digestion cell. An increase in oxidation potential or current can increase the efficiency of the oxidation process.

[0032] If the predetermined value is reached, the increasing slope of oxidation of the PFAS compound and the resulting fluoride is reached, and the method and system can proceed to the next step in which the signal is compared to a threshold. If the signal is less than or equal to the threshold, the oxidation is complete. If the signal is not equal to or less than the threshold, the oxidation potential can be adjusted or optimized.

[0033] Reference Figure 2 , in one embodiment, a stabilization module for a fluoride ISE recirculation path is shown. A non-oxidizing cell is shown. The ISE can be used to measure the sample. The measurements can be for fluoride, pH, carbon dioxide, etc. The cell can be designed with contacts that allow for faster thermal equilibrium and a reservoir for creating isothermal conditions. The cell can have at least one influent and at least one effluent. The cell can be fluidly connected to an oxidizing cell. The sample can be stirred, and the chamber is designed to minimize bubble interference near the ISE electrode.

[0034] Reference Figure 3A and Figure 3B , in one embodiment, a dynamic endpoint determination is shown to ensure digestion is complete. Figure 3AIn, an exemplary dynamic endpoint detection in the case of 50 ppb (parts per billion) of PFOA and 50 ppb of inorganic fluoride is shown. Before oxidation, initial inorganic fluoride and total inorganic fluoride can be measured. Before oxidation, the sample can be circulated between the oxidation pool and the non-oxidation pool, wherein for the initial part of the scheme, the oxidation pool does not apply an electric potential. Afterwards, an electric potential can be applied to the portion of the sample in the oxidation pool. Measurements can be made in a non-oxidation pool or a reservoir pool. The oxidation of PFOA increases the concentration of free fluoride in the solution. In one embodiment, the method described above for dynamic endpoint detection can be used to optimize oxidation and oxidation potential. The increase in the fluoride ISE signal after oxidation can represent the amount of the total organic fluoride component in the sample. In addition, the sum of the total inorganic fluoride and total organic fluoride signals gives the measurement result of total fluoride. The total organic fluoride concentration can be measured by the oxidation of PFOA compounds. Although this specification uses PFOA as an example, other analytes may be measured, such as organometallics, solid metals, organosulfates, or organophosphates, such as but not limited to iron, nickel, cadmium, mercury, lead, and the like.

[0035] In one embodiment, the threshold value may be zero, close to zero, or approximately the value of the background signal of the measurement system. For example, the background may be Figure 3A The slope of the parallel dashed lines in . The background can define the asymptotes of the measurement system. Background or instrument related background or system contribution variables can depend on a variety of variables, such as the oxidation rate constant at the surface of the boron-doped diamond electrode, the penetration depth and diffusion rate of hydroxyl radicals, the total volume of the oxidation pool, and / or the exchange rate of the sample between the oxidation pool and the non-oxidation pool. The method and system can monitor these system contributions. The method or system can determine whether a variable or system contribution approaches or exceeds a threshold, range or value. Such monitoring can alert the user or system to poor performance, maintenance, recalibration, etc. The output can be in any form, such as an alarm, visual prompt, auditory feedback, event recorder, etc.

[0036] Reference Figure 3B , in one embodiment, shows Figure 3A The first derivative of similar measurements can be plotted against time. In other words, the first derivative of ppb / minute of fluoride can be plotted against time. Oxidation can continue until a threshold is reached. As an example, the threshold reached by the endpoint of 50 ppb PFOA is shown. As another example, the endpoint of 250 ppb PFOA is also shown. The duration and oxidation potential of the protocol can be optimized for a given PFOA (or other ISE electrode measurement) concentration. The method and apparatus can reduce experimental time and power consumption while ensuring complete oxidation.

[0037] Reference Figure 4A and Figure 4B , in one embodiment, a sample oxidation curve is shown. In one embodiment, oxidation can be stopped and started oxidation. When the digestion is stopped, an increase in fluoride concentration can be observed. During the digestion, the temperature can be increased. In one embodiment, in order to deconvolute the effects of oxidation and digestion on fluoride concentration and temperature, oxidation can be stopped and fluoride measurements can be recorded. Figure 4A The PFOA oxidation curve during the equilibrium between 5 minute digestions is shown. In other words, during the pause in the digestion, the temperature can be reduced from the higher temperature during the digestion. This method enables the determination of any fluoride concentration component caused by the elevated temperature. In addition, the high potential, such as 60 volts and 300 milliamps, may interfere with the relatively small voltage measured at the ISE electrode. In one embodiment, Figure 4B Shown are the fluoride concentrations measured by the ISE electrode for the last 2 minutes of the equilibration step in the presence of 1 ppm PFOA.

[0038] Reference Figure 5A and Figure 5B , in one embodiment, a calibration curve for a dynamic endpoint assay is shown. Figure 5A The oxidation curve of PFOA is shown or the concentration is shown, which shows the fluoride concentration over time as measured by ISE. Figure 5B Shows Figure 5A In other words, the method and system can be used to measure fluoride concentrations over a wide range of PFOA concentrations.

[0039] The described methods and systems can simplify the analysis or measurement of total organic fluoride, total inorganic and total fluoride. For example, the elimination of the combustion cartridge is achieved, thereby avoiding the generation of hydrogen fluoride gas in existing adsorbable organic fluoride (AOF). In addition, the system and method can produce oxidants without the use of reagents during the digestion process. In addition, on the BDD electrode, the efficiency of hydroxyl radical generation can be higher because there is a weak interaction between the radicals and BDD. The robustness of BDD provides long-term stability under harsh conditions, high current density, fluctuating pH and complex solution matrices. In addition, optionally, a bipolar electrode configuration is used to improve the oxidation efficiency. In addition, the method and system can optimize the time and / or power consumption of the measurement process.

[0040] At the BDD electrode, PFAS can be directly oxidized to carbon dioxide and fluoride. This may happen for lower chain PFAS compounds. PFAS can be indirectly oxidized by hydroxyl radicals. Hydroxyl radicals can be produced in two ways. Water oxidation can produce hydrogen peroxide or oxygen. Hydrogen peroxide can dissociate to form hydroxyl radicals. Oxygen can form superoxide, which then reacts with protons to form hydrogen peroxide. The hydrogen peroxide can then dissociate and produce hydroxyl radicals. In one embodiment, at the counter electrode, water can be reduced to form hydroxide anions and hydrogen.

[0041] The method and system can determine the amount of TOF and / or TIF of a sample. The system can output the amount of total organic fluoride, total inorganic fluoride, total fluoride, PFAS concentration, etc. of the sample. The system can also output parameters such as flow rate, amperage, digestion time, etc. In one embodiment, the output can be in the form of display, storage of data in a memory device, sending output through a connected system or wireless system, printout, etc. The system can be automated, which means that the system can automatically output the measurement results. The system can also have associated alarms, limits, or predetermined thresholds. For example, if the measured value reaches a threshold, the system can trigger an alarm, alert the system / personnel that an error has occurred, change the flow rate of the aqueous solution, etc. The data can be analyzed in real time, stored for later use, or any combination thereof. If the measured amount cannot be determined, the system can obtain another sample for testing, output an alarm, send a maintenance reminder, divert the sample flow, etc.

[0042] Aqueous samples can be put into or introduced into oxidation ponds, non-oxidation ponds, etc. manually or by using mechanical means (e.g., gravity flow, pump, pressure, fluid flow, etc.) by the user. For example, the water sample for testing can be introduced into the chamber by a pump. In one embodiment, there can be one or more chambers in which one or more method steps can be carried out. In one embodiment, valves, etc. can control the inflow and outflow of samples into or out of one or more chambers (if present). Once the sample is introduced into the measurement system, the system can automatically measure the sample.

[0043] In one embodiment, the electrode can be completely or at least partially arranged in the volume of the aqueous solution or sample. For example, if the sample is introduced into a chamber with one or more electrodes, the aqueous solution can at least partially cover the one or more electrodes. As another example, one or more electrodes can be partially arranged in the chamber, while other parts of the electrodes are outside the chamber. Therefore, when the aqueous solution is introduced into the chamber, it only covers the part of the electrode in the chamber.

[0044] Therefore, each embodiment described herein represents a technical improvement to conventional methods and instruments for measuring PFAS, fluoride or other analytes. Using the technology described herein, one embodiment can use methods and apparatus for instruments for measuring PFAS. This is in contrast to conventional methods with the above limitations. Such technology provides a better construction method and an instrument for measuring PFAS.

[0045] Although various other circuits, circuit systems or components may be used in the information processing device, with respect to the instrument for fluoride measurement according to any one of the embodiments described herein, Figure 6 An example is shown in . The device circuit system 10' may include a measurement system based on a created chip design, for example, a specific computing platform (e.g., mobile computing, desktop computing, etc.). Software and one or more processors are combined in a single chip 11'. It is well known in the art that a processor includes an internal arithmetic unit, registers, cache memory, bus, I / O ports, etc. The internal bus, etc. depends on different vendors, but basically all peripheral devices (12') can be connected to a single chip 11'. The circuit system 10' combines the processor, memory control, and I / O controller center into a single chip 11'. In addition, this type of system 10' generally does not use SATA or PCI or LPC. For example, common interfaces include SDIO and I2C.

[0046] There are one or more power management chips 13', e.g., a battery management unit (BMU), which manages power supplied, e.g., by a rechargeable battery 14', which can be recharged by connection to a power source (not shown). In at least one design, a single chip such as 11' is used to provide BIOS-like functions and DRAM storage.

[0047] The system 10' typically includes one or more of a WWAN transceiver 15' and a WLAN transceiver 16' for connecting to various networks such as radio communication networks and wireless Internet devices (e.g., access points). In addition, devices 12' are generally included, such as transmit and receive antennas, oscillators, PLLs, etc. The system 10' includes input / output devices 17' for data input and display / rendering (e.g., a computing location located away from the single beam system that is easily accessible to the user). The system 10' typically also includes various memory devices, such as flash memory 18' and SDRAM 19'.

[0048] It can be understood from the foregoing that the electronic components of one or more systems or devices may include, but are not limited to: at least one processing unit, memory, and a communication bus or communication device connecting each element (including memory) to the one or more processors. The system or device may include or access various device-readable media. The system memory may include device-readable storage media in the form of volatile and / or non-volatile memory (such as read-only memory (ROM) and / or random access memory (RAM)). By way of example but not limitation, the system memory may also include an operating system, application programs, other program modules, and program data. The disclosed system may be used in an embodiment of an instrument for fluoride measurement.

[0049] Those skilled in the art will appreciate that various aspects may be implemented as systems, methods, or device program products. Thus, various aspects may take the form of a complete hardware implementation or an implementation including software, which may all be collectively referred to herein as a "circuit," "module," or "system." Additionally, various aspects may take the form of a device program product embodied in one or more device-readable media containing device-readable program code.

[0050] It should be noted that the various functions described herein can be implemented using instructions stored on a device-readable storage medium (such as a non-signal storage device), where the instructions are executed by a processor. In the context of this article, a storage device is not a signal, and "non-transient" includes all media except signal media.

[0051] The program code for implementing the operation can be written in any combination of one or more programming languages. The program code can be executed completely on a single device, partially on a single device, as an independent software package, partially on a single device and partially on another device or completely on other devices. In some cases, the device can be connected by any type of connection or network (including local area network (LAN) or wide area network (WAN)), or can be connected by other devices (for example, by using the Internet of an Internet service provider), by wireless connection (for example, near field communication) or by hard wire connection (such as by USB connection).

[0052] Exemplary embodiments are described herein with reference to the accompanying drawings, which illustrate exemplary methods, devices, and products according to various exemplary embodiments. It is to be understood that actions and functions may be implemented at least in part by program instructions. These program instructions may be provided to a device (e.g., Figure 6 The measuring device shown) or other programmable data processing device processor to produce a machine so that the instructions executed by the processor of the device implement specified functions / actions.

[0053] It should be noted that the values ​​provided herein should be interpreted to include equivalent values ​​indicated by the use of the term “about.” Equivalent values ​​will be apparent to one of ordinary skill in the art, but at least include values ​​obtained by ordinary rounding of the last significant digit.

[0054] The present disclosure has been provided for illustration and description, but is not intended to be exhaustive or limiting. Many changes and variations will be apparent to those of ordinary skill in the art. Exemplary embodiments are chosen and described to explain principles and practical applications, and to enable those of ordinary skill in the art to understand the disclosure of multiple embodiments with a variety of changes suitable for the intended specific use.

[0055] Thus, although the illustrated exemplary embodiments have been described herein with reference to the accompanying drawings, it should be understood that this description is not limiting and that various other changes and modifications may be implemented therein by those skilled in the art without departing from the scope and spirit of the present disclosure.

Claims

1. A method for measuring the amount of total organic fluoride content of a PFAS-containing sample, the method comprising: placing a sample containing a PFAS compound into a measuring device, wherein the measuring device comprises an oxidizing cell and a non-oxidizing cell, wherein the oxidizing cell comprises a boron-doped diamond electrode; measuring the amount of total inorganic fluoride in the sample before oxidation using the measuring device; applying an electric potential to a portion of the sample in the oxidation cell, wherein the electric potential oxidizes the PFAS compound; measuring the amount of total organic fluoride of the sample after the oxidation using the measuring device to provide a measurement signal of the total organic fluoride; as well as The first derivative of the total organic fluoride measurement signal is determined.

2. The method of claim 1, wherein the sample is circulated between the oxidation tank and the non-oxidation tank.

3. The method of claim 1, wherein the potential is a step-wise continuous electrochemical oxidation. 4 . The method of claim 1 , further comprising determining a second derivative of the total organic fluoride measurement signal.

5. The method of claim 1, further comprising comparing the first order derivative to a predetermined value, wherein if the first order derivative is greater than the predetermined value, optimizing the potential provided to the oxidation tank.

6. The method of claim 1, further comprising comparing the first order derivative to a threshold value, wherein if the first order derivative is greater than the predetermined value, providing a stepwise continuous oxidation of the PFAS compound in the oxidation tank.

7. The method of claim 1 further comprising periodically shutting down the electrical potential provided to the oxidation bath for temperature stabilization.

8. The method of claim 1, further comprising periodically shutting down the electrical potential provided to the oxidation cell to reduce electrical noise measured by the measuring device.

9. The method of claim 1, further comprising shielding the measurement device from a voltage potential applied during the oxidation.

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

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

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

13. The method of claim 13, wherein the first derivative approaching an asymptote defines a kinetic endpoint of the oxidation.

14. The method of claim 1, wherein the total fluoride content is equal to the sum of the total inorganic fluoride and the total organic fluoride.

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

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

17. The method of claim 16, wherein the linear background comprises a system contribution variable, wherein the system contribution variable is selected from the group consisting of: an oxidation rate constant at the surface of the boron-doped diamond electrode, a penetration depth and a diffusion rate of hydroxyl radicals, a total volume of the oxidation pool, and an exchange rate of the sample between the oxidation pool and the non-oxidation pool.

18. The method of claim 1, wherein the measuring device is selected from the group consisting of an electrochemical device and an optical device.

19. A method for measuring the amount of an analyte in a sample, the method comprising: placing the sample in a measuring device, wherein the measuring device comprises an oxidation cell and a non-oxidation cell, wherein the oxidation cell comprises a boron-doped diamond electrode; measuring an amount of a first component of the sample prior to oxidation using the measurement device, wherein an ion selective electrode measures the first component; applying an electric potential to a portion of the sample in the oxidation cell, wherein the electric potential oxidizes the sample; as well as The amount of a second component of the sample after the oxidation is measured using the measuring device, wherein another ion selective electrode measures the second component.

20. A device for measuring the amount of total organic fluoride content of PFAS compounds in a sample, the device comprising: Non-oxidizing ponds; an oxidation tank comprising an ion selective electrode and a boron-doped diamond electrode; processor; The apparatus for measuring the amount of fluoride content of a PFAS compound in a sample is configured to: measuring the amount of total inorganic fluoride in the sample before oxidation using the measuring device; applying an electric potential to a portion of the sample in the oxidation cell, wherein the electric potential oxidizes the PFAS compound; measuring the amount of total organic fluoride of the sample after the oxidation using the measuring device to provide a measurement signal of the total organic fluoride; as well as The first derivative of the total organic fluoride measurement signal is determined.

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