Patent Description:
Ensuring water quality is critical to the health and well-being of humans, animals, and plants, which are reliant on water for survival. One parameter of water that may be measured is the pH. The measurement of pH of an aqueous sample is critical in a number of industries such as pharmaceuticals, biomedical, water supply, and other manufacturing fields. Measurement of pH may allow for proper treatment of water or ensuring proper water quality for sensitive purposes, and allows for identifying the overall quality of the water. One method to measure pH in an aqueous sample includes the use of electrodes which require constant maintenance and calibration of the pH measurement system.

Document <CIT>, with its abstract, discloses a combination pH and CO2 sensor employing separate sensors. Each sensor has a wire with an electrochemically active layer, an electrolyte layer and a membrane between the electrolyte layer and the fluid to be tested. Each electrolyte layer is constructed of a dried residue which can be easily stored and which must be rehydrated prior to the first use. The electrolyte layer in the pH sensor when hydrated forms an aqueous solution buffered against changes in pH due to changes in the dissolved CO2 concentration and is preferably formed of <NUM>-(n-morpholino) ethanesulfonic acid, <NUM>-(n-morpholino) ethanesulfonic acid - sodium salt and potassium chloride. The electrolyte layer in the CO2 sensor when hydrated forms an aqueous solution having bicarbonate ions and is preferably formed of polyvinyl alcohol, sodium chloride and sodium bicarbonate. The electrical potential at the pH sensor is proportional to the pH of the fluid. The electrical potential difference between the CO2 sensor and the pH sensor is proportional to the concentration of dissolved CO2 in the fluid.

Document <CIT>, with its abstract, discloses a method for calibration of a potentiometric sensor comprising: selection of at least three calibration solutions all containing a well-known different concentration of the ion or the dissolved gas and at least one of the calibration solutions having a concentration which according to the response equation falls between the lower linearity limit point and the sensitivity limit point, measurement of the potential of each of these solutions, insertion of these values of potential and concentration into a theoretical response equation for the sensor, determination of the values of the unknowna, and determination of the response equation for the sensor by inserting the unknown values into the theoretical equation.

Document <CIT>, with its abstract, discloses a sensing apparatus comprising an ion sensitive field effect transistor arranged to generate an electrical output signal in response to localised fluctuations of ionic charge at or adjacent the surface of the transistor, and means for detecting the electrical output signal from the ion sensitive field effect transistor, the localised fluctuations of ionic charge indicating events occurring during a chemical reaction.

Document <CIT>, with its abstract, discloses an electrode for the determination of pH which is made by depositing a phenolic compound on a conductive substrate, where the phenolic compound has a phenolic hydroxy group attached to a carbon atom on an aromatic ring and also has an oxygen atom connected through one other atom to an adjacent carbon atom of the aromatic ring such that this oxygen atom can form a hydrogen bond to the phenolic hydroxy group; and then electrochemically oxidising the immobilized phenolic compound in a one electron one proton oxidation so as to form a polymeric, water-insoluble, redox-active deposit on the conductive substrate.

In summary, the present disclosure provides a method for measuring pH in an aqueous sample with a frit-less electrode, comprising the steps described at claim <NUM>. The dependent claims outline advantageous ways of carrying out the method.

Additionally, the present disclosure provides a measurement device for measuring pH in an aqueous sample with a frit-less electrode, comprising the features described at claim <NUM>. The dependent claims outline advantageous forms of embodiment of the measurement device.

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 pointed out in the appended claims.

The measurement of the pH of water or other aqueous solutions or samples is very common and allows for determination of the quality or other characteristics of the aqueous solution. Conventional pH measurement instruments are available; however, these instruments are complex, and require constant maintenance and calibration. For example, traditional pH measurements use a pH electrode that is introduced into an aqueous sample. To measure the pH of the sample, the pH electrode includes an internal solution that is used as a reference for the measurements taken within the aqueous sample. Thus, the conventional pH measurement devices require that a user manually add the internal solution to the electrode.

The internal solution that is used in conventional pH measurement electrodes is often a high molar potassium chloride solution. Many pH electrodes contain a filling port for the internal or reference solution that must be closed to prevent evaporation of the reference solution. Failure to close this port leads to evaporation and an increase in the molarity of the internal reference solution. This rise in molarity can alter the sensitivity of the pH electrode and also lead to crystallization of salts in the pH electrode, thereby damaging the electrode.

Additionally, conventional pH electrodes contain a frit. The frit serves as an electrically conductive "wick" between the electrode filing solution and the aqueous sample to be measured. The frit allows electrical conductivity while keeping the internal solution and aqueous sample as separate volumes. This frit requires maintenance, such as cleaning of the frit to prevent fouling. If the frit fouls the electrode would require recalibration and maintenance. Additionally, the frit is susceptible to drying out. Thus, the conventional pH measurement electrodes need to be stored in an aqueous environment to minimize damaging the electrode by allowing the frit to dry. Failure to maintain a proper internal solution or frit can damage a pH electrode, lower the sensitivity, or render the electrode inoperative. Additionally, the frit and filling solution may cause junction potentials, which may affect the measurement of the pH electrode.

Additionally, conventional pH electrodes may be constructed using fragile, thin glass. This glass breaks easily leading to higher replacement and maintenance costs. Conventional pH electrodes also may have "alkali errors. " These errors arise from interfering ions such as sodium and lithium affecting the pH response at high pH values. What is needed is a pH measurement electrode that requires less maintenance while maintaining the sensitivity of pH measurement.

Accordingly, the method and device described herein provide a technique for pH measurement using a frit-less and internal solution free electrode that is able to measure electrical signals and identify the portion of the electrical signal that is associated with interferants and the electrical signal that is a result of the pH of the aqueous sample. Specifically, the method and device as described herein are able to identify an electrical potential of an aqueous sample using an electrode sensitive to interferants, and an electrode sensitive to both the interferants and the pH of an aqueous sample. In other words, in an embodiment, an electrode may be of a material sensitive to interferants and/or interferants and pH in an aqueous sample. For example, electrodes may comprise Sp2 and/or Sp3 carbon materials that can include diamond-like materials doped with elements like boron (BDD). In this case the first electrode includes a localized microelectrode or nanoelectrode array of SP2 carbon on the SP3 substrate that will be sensitive to interferants and pH, whereas the second electrode will be include SP3 substrate which will be sensitive to only interferants. Other materials may include metallic systems, where, in this case the first electrode includes localized iridium oxide micro or nano-electrodes on a conductive iridium metal substrate which would be sensitive to both pH and interferants, whereas the second electrode will be include just iridium metal which will be sensitive to only interferants.

Other proton sensitive/insensitive metal oxide/metal systems include tin, tungsten, palladium, rhodium, platinum, osmium, tantalum, vanadium. Other proton sensitive/insensitive carbonaceous systems include, modified CNT, graphene nanocellulose. By incorporating silicon oxide micro/nanostructures on conductive or semi-conductive silicon substrates, a first electrode glass system that is sensitive to interferants and pH can achieved. The second electrode will include just the silicon substrate without any silicon oxide which will be sensitive to interferants but not the pH, which will be a reference-free glass electrode. By taking both measurements, the system can subtract the measurement associated with the interferants from the overall measurement to then identify the pH of the aqueous sample. To conduct these measurements the system may include a common ground electrode or reference electrode. Thus, the method may use a sequence of measurements as a means to quantify the interferant species.

The use of BDD serves as a better electrode material than other carbon-based or metallic materials (e.g., silver, gold, mercury, nickel, etc.) because these materials may eventually themselves become oxidized, thereby generating interfering signals and contributing to the errors in the measurement of pH. Thin film BDD electrodes may undergo thermal stress because of the different thermal expansion coefficients between the substrate and the BDD layer, which limits the current density that can be applied to these electrodes. Thick BDD solid electrodes do not have the substrate and therefore the structural and electrical integrity may be maintained at a higher current. The lack of substrate in the thick, solid, free-standing BDD electrode eliminates the problem of delamination that can occur on thin-filmed BDD materials. Thus, the electrodes used in the measurement device as described may be thick-filmed BDD electrodes.

In an embodiment, an aqueous sample is introduced into a measurement chamber. Alternatively, the pH measurement apparatus is introduced into an aqueous sample. A first potential measured across a first electrode and a ground electrode is measured. This first potential is associated with a measure of the interferants in the aqueous sample. A second potential measured across a second electrode and the ground electrode is also measured. The ground electrode associated with the measurement of the second potential may be the same ground electrode used in measurement of the first potential. The second potential is associated with both the interferants and a pH of the aqueous sample. In an embodiment, the second potential is subtracted from the first potential to remove an interferant component of the measurement to identify a pH of an aqueous sample. The method therefore mathematically accounts for interferants by utilization of the two or more electrical responses to remove the charge delivered to interferant species that may result in false pH identification, without the use of an electrode including a frit or internal reference solution.

The illustrated example embodiments will be best understood by reference to the figures. The following description is intended only by way of example, and simply illustrates certain example embodiments.

While various other circuits, circuitry or components may be utilized in information handling devices, with regard to an instrument for pH measurement according to any one of the various embodiments described herein, an example is illustrated in <FIG>. Device circuitry <NUM> may include a measurement system on a chip design found, for example, a particular computing platform (e.g., mobile computing, desktop computing, etc.) Software and processor(s) are combined in a single chip <NUM>. Processors comprise internal arithmetic units, registers, cache memory, busses, I/O ports, etc., as is well known in the art. Internal busses and the like depend on different vendors, but essentially all the peripheral devices (<NUM>) may attach to a single chip <NUM>. The circuitry <NUM> combines the processor, memory control, and I/O controller hub all into a single chip <NUM>. Also, systems <NUM> of this type do not typically use SATA or PCI or LPC. Common interfaces, for example, include SDIO and I2C.

There are power management chip(s) <NUM>, e.g., a battery management unit, BMU, which manage power as supplied, for example, via a rechargeable battery <NUM>, which may be recharged by a connection to a power source (not shown). In at least one design, a single chip, such as <NUM>, is used to supply BIOS like functionality and DRAM memory.

System <NUM> typically includes one or more of a WWAN transceiver <NUM> and a WLAN transceiver <NUM> for connecting to various networks, such as telecommunications networks and wireless Internet devices, e.g., access points. Additionally, devices <NUM> are commonly included, e.g., a transmit and receive antenna, oscillators, PLLs, etc. System <NUM> includes input/output devices <NUM> for data input and display/rendering (e.g., a computing location located away from the single beam system that is easily accessible by a user). System <NUM> also typically includes various memory devices, for example flash memory <NUM> and SDRAM <NUM>.

It can be appreciated from the foregoing that electronic components of one or more systems or devices may include, but are not limited to, at least one processing unit, a memory, and a communication bus or communication means that couples various components including the memory to the processing unit(s). A system or device may include or have access to a variety of device readable media. System memory may include device readable storage media in the form of volatile and/or nonvolatile memory such as read only memory (ROM) and/or random access memory (RAM). By way of example, and not limitation, 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 to perform pH measurement of an aqueous sample.

Referring now to <FIG>, an embodiment measures pH in an aqueous solution using frit-less electrodes that do not require an internal reference solution. In other words, the electrodes do not require a filling solution, a frit, and are made of a material other than the fragile, thin glass of conventional electrodes. The method and device as described herein provide a technique for interferants-free measurement for pH that can be used in practice with actual aqueous samples without the recalibration and maintenance required by conventional systems, due to the removal of the components that cause maintenance requirements and calibration.

At <NUM>, the measurement apparatus is introduced into an aqueous sample. Alternatively, an aqueous sample is introduced into a test chamber, for example, a test chamber of a measurement device. If the aqueous sample is introduced into the measurement device, the aqueous sample is placed or introduced into a test chamber manually by a user or using a mechanical means, for example, gravity flow, a pump, pressure, fluid flow, or the like. For example, a water sample for pH testing is introduced to a measurement or test chamber using a pump. Valves or the like control the influx and efflux of the aqueous solution into or out of the one or more chambers, if present. Once the sample is introduced to the measurement system, the system measures the pH of the sample, using steps as explained in more detail below. The measurement device may include one or more chambers in which the one or more method steps are performed.

The measurement device includes at least three electrodes for measuring the pH of an aqueous sample, namely a first measurement electrode, a second measurement electrode, and a ground (reference) electrode. The ground electrode may be shared by the first measurement electrode and the second measurement electrode. In other words, both the first and second measurement electrode may be electrically connected to the ground or reference electrode and the ground or reference electrode may be used by both measurement electrodes for completing the electrical circuit. One or more measurement electrodes may be constructed of the same or different materials. For example, one measurement electrode may be constructed of a material that is insensitive to analytes, for example, Sp3/phase pure Boron doped diamond material, whereas a second measurement electrode may be constructed of a material that is sensitive to analytes, for example, Sp2/Sp3 Boron doped diamond or other carbon material.

The electrodes may be fully or at least partially disposed in the volume of aqueous solution. For example, if the aqueous solution is introduced into a chamber having one or more electrodes, the aqueous solution may at least partially cover the one or more electrodes. As another example, the one or more electrodes may be partially disposed within the chamber with the other portion of the electrode outside the chamber. Thus, when the aqueous solution is introduced into the chamber it only covers the portion of the electrodes that are within the chamber.

At <NUM>, the system measures a first electrical potential of the volume of aqueous solution in a chamber via application of an electrical signal across a first measurement electrode and the reference electrode. The use of the term "first" or "second" is not intended to designate either a temporal indication of when the measurement is taken or a location of one electrode with respect to another. Rather, the terms "first" and "second" are merely used to distinguish between two different electrodes.

The electrical signal may be applied using or across one or more electrodes, for example, a series of electrodes. The first measurement electrode is used to measure the electrical potential associated with any interferants in the aqueous sample. Thus, the first measurement electrode is constructed of an analyte insensitive material, for example, Sp3 boron doped diamond (BDD) electrode material. The Sp3BDD electrode may be alumina polished. The Sp3 BDD electrode may be phase pure. The Sp3 BDD electrode may be polarized, for example, using electrochemical procedures, to render a uniform, clean and homogenous substrate. This can be done in <NUM> H2SO4 at 3V for <NUM> seconds. A Sp3 electrode is insensitive to pH measurement alone. The particular pH insensitivity of the Sp3 BDD electrode is due to the pH response of the electrode is within <NUM> - <NUM> mV/pH. Thus, this type of material is useful for measuring electrical potential that is independent of pH. Therefore, the resulting potential measurement is associated with any interferants in the aqueous sample. The application of an electrical signal across the first electrode and the ground electrode allows for measurement of a first electrical potential.

At <NUM>, the system measures a second electrical potential of the volume of aqueous solution in a chamber via application of an electrical signal across a second measurement electrode and the ground electrode. The ground electrode used for the second measurement may be the same ground electrode used for the first measurement in order to ensure that the measurements are consistent and with reference to the same measurement. In other words, the use of a single ground electrode accounts for any noise or electrical imperfections that may be associated with the ground electrode itself. As with the first measurement, the electrical signal for the second measurement may also be applied using one or more electrodes, for example, a series of electrodes.

The second measurement electrode is constructed of an analyte sensitive material, for example, Sp2/Sp3 boron doped diamond (BDD) electrode material. A controlled amount of Sp2 carbon (e.g., a non-diamond material such as glassy carbon containing Sp2 carbon, etc.) is introduced into or onto the Sp3 BDD carbon, thereby creating a Sp2/Sp3 BDD electrode. For example, the Sp2 carbon may be introduced into the Sp3 BDD electrode using laser patterning, resulting in a polycrystalline boron doped diamond material that exhibits the benefits of glassy carbon electrode with respect to pH measurement while producing low background currents due to a BDD substrate. Introduction of the Sp2 carbon into the Sp3 BDD carbon enables the measurement of pH. Thus, as opposed to the Sp3 BDD electrode, the Sp2/Sp3 electrode is sensitive to pH. Therefore, the Sp2/Sp3 electrode is sensitive to both interferants and pH. The introduction of the Sp2 results in an electrode that can make a pH determination having a <NUM> mV/pH +/- <NUM> mV sensitivity. Since the second measurement electrode is sensitive to analyte, the potential measured across the second measurement electrode and the ground electrode is associated not only with the interferants in the sample, but also the pH of the sample.

A first measuring electrode and a second measuring electrode is used to measure a potential in an aqueous solution with reference to a ground electrode (ground rod or reference electrode). The ground electrode may be the same for both the first measuring electrode and the second measuring electrode. Use of a single ground rod with multiple measuring electrodes may compensate for electrical potential, conductivity, oxidation-reduction potential (ORP), or the like across multiple potential measurements of the aqueous sample. The ground electrode may contain or be made of titanium (Ti), platinum (Pt), or any other conductive metal that may not foul easily. The one or more series of electrodes may be boron doped diamond (BDD) electrodes.

At <NUM>, the system determines or identifies a pH of the aqueous sample. To make this determination, the system subtracts the electrical potential associated with the interferants of the aqueous sample from the electrical potential associated with the interferants and pH to give a resulting pH of the aqueous sample. For example, the open circuit potential measured from the Sp3 BDD material is the electrical potential associated with interferants minus the electrical potential of the ground. The open circuit potential measured from the Sp2/Sp3 material (BDD, glassy carbon, etc.) is the electrical potential associated with both pH and interferants. Thus, in this example, to identify the electrical potential associated with the pH of the sample, the measured electrical potential of measured at the first measurement electrode is subtracted from the measured electrical potential measured at the second measurement electrode. Referring to <FIG>, a voltammetry approach for determining a pH measurement may be used. For example, a scan for voltammetry is commenced from the open circuit potential for each aqueous sample. The difference between a peak potential and a starting potential identifies a dependence of peak. A differential potential measured between the open circuit potential and the peak potential eliminates the floating nature of the ground electrode itself. Examples of a method may be found in <FIG> and <FIG>.

If the system cannot identify a pH of the aqueous solution, the system continues to measure electrical responses from the electrodes of the system at <NUM>. Additionally or alternatively, the system may trigger an alarm, shut down, alter flow control of the aqueous sample, or the like. However, if, at <NUM>, a pH of the aqueous sample may be determined, the system outputs the pH of an aqueous solution. An output may be in the form of a display, storing the data to a memory device, sending the output through a connected or wireless system, printing the output, or the like. The system may be automated, meaning the system may automatically output the identified pH. The system may also have associated alarms, limits, or predetermined thresholds. For example, if a measured pH reaches a threshold, the system may trigger an alarm, adjust the pH of the aqueous solution, alter the flow of the aqueous solution, or the like. Data may be analyzed in real-time, stored for later use, or any combination thereof.

Referring to <FIG> and <FIG>, circuitry controls the electrical signal and or measurement (e. g, current, voltage, etc.) to one or more series of electrodes such that different electrical signals are applied and/or measured with respect to the volume of aqueous solution. The first measurement electrode and second measurement electrode are connected to a solid state differential pH measurement circuitry with internal referencing. In the case that multiple or a series of electrodes are included in the system, each electrode may correspond to a different electrical signal value. For example, a first electrode may correspond to a first electrical signal value, a second electrode may correspond to a second electrical signal value, and the like. Each of these different electrical signal values provides an electrical signal that will measure the interferants and/or pH of an aqueous sample. Thus, as the system provides electrical signals to each of the electrodes in series, the system applies different electrical signals to or measure different electrical signals at the single electrode. In either case, after each application of an electrical signal, the system measures the pH of the aqueous solution. Other electrodes may be included to complete the electrical circuit or to provide a reference electrode for measurement, for example, ground electrodes, multiple measuring electrodes, or the like. The circuitry of <FIG> and <FIG> are example embodiments and not meant to be limiting. The circuitry of <FIG> represents an example embodiment for BDD voltammetry with reference offset cancellation. The circuitry of <FIG> illustrates an example embodiment for BDD voltammetry with differential measurement of resting potential and response current.

As will be appreciated by one skilled in the art, various aspects may be embodied as a system, method or device program product. Accordingly, aspects may take the form of an entirely hardware embodiment or an embodiment including software that may all generally be referred to herein as a "circuit," "module" or "system. " Furthermore, aspects may take the form of a device program product embodied in one or more device readable medium(s) having device readable program code embodied therewith.

It should be noted that the various functions described herein may 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 document, a storage device is not a signal and "non-transitory" includes all media except signal media.

Program code for carrying out operations may be written in any combination of one or more programming languages. The program code may execute entirely on a single device, partly on a single device, as a stand-alone software package, partly on single device and partly on another device, or entirely on the other device. In some cases, the devices may be connected through any type of connection or network, including a local area network (LAN) or a wide area network (WAN), or the connection may be made through other devices (for example, through the Internet using an Internet Service Provider), through wireless connections, e.g., near-field communication, or through a hard wire connection, such as over a USB connection.

Claim 1:
A method for measuring pH in an aqueous sample with a frit-less electrode, comprising:
introducing (<NUM>) an aqueous sample into a measurement device comprising at least three electrodes, wherein at least one electrode of the at least three electrodes comprises a ground rod electrode, wherein at least one electrode of the at least three electrodes comprises a first measurement electrode, and wherein at least one electrode of the at least three electrodes comprises a second measurement electrode, wherein the first measurement electrode comprises a material that is pH insensitive and sensitive to components in the aqueous sample interfering with pH measurement, whereby the second measurement electrode comprises a material that is sensitive to both pH and components in the aqueous sample interfering with pH measurement;
measuring (<NUM>) a first electrical potential between the first measurement electrode and the ground rod electrode in the aqueous sample;
measuring (<NUM>) a second electrical potential between the second measurement electrode and the ground rod electrode in the aqueous sample; and
identifying (<NUM>) a pH of the aqueous sample based upon a difference between the first electrical potential and the second electrical potential.