Square wave voltammetry with repeated cycles

Abstract

One embodiment provides a method of measuring components of an aqueous sample using square wave voltammetry, comprising: introducing the aqueous sample into a chamber of a square wave voltammetry apparatus; applying a step of a stimulus voltage comprising a staircase voltage to the aqueous sample, each step of the staircase voltage defining a group and having two or more repeating square wave modulations of equal voltage amplitude; measuring the resulting composite current output from the stimulus voltage by a measurement comprising square wave voltammetry; and averaging the composite current output over at least two or more cycles of each of the groups.

Description

[Technical field]

[0001] This application claims priority to U.S. patent application Ser. No. 17 / 698,263, entitled "REPEATED CYCLES SQUARE WAVE VOLTAMMETRY," filed March 18, 2022, the contents of which are incorporated herein by reference.

[0002] This application relates generally to the measurement of chemical species in solution using square wave voltammetry, and more particularly to voltammetry using repeated cycles in aqueous samples. [Background technology]

[0003] Voltammetry is a technique used in electrochemical measurements. It involves applying a varying voltage between two electrodes in a solution and recording the resulting current response. Typically, this current response is measured at a third electrode. The resulting curve of response current versus applied voltage provides useful information about the fluid sample being measured. A typical voltammogram shows one or more quasi-Gaussian response peaks, the peak positions of which are related to the redox potentials of the chemical species in the solution being analyzed. Summary of the Invention [Means for solving the problem]

[0004] In summary, one embodiment provides a method for measuring components of an aqueous sample using square wave voltammetry, comprising: introducing the aqueous sample into a chamber of a square wave voltammetry apparatus; applying a step of a stimulus voltage to the aqueous sample, the stimulus voltage step comprising a staircase voltage, each step of the staircase voltage defining a group and having two or more repeating square wave modulations of equal voltage amplitude; measuring the resulting composite current output from the stimulus voltage by a measurement comprising square wave voltammetry; and averaging the composite current output over at least two or more cycles of each of the groups.

[0005] In another embodiment, an apparatus is provided for measuring components of an aqueous sample using square wave voltammetry, the apparatus comprising a voltammetry electrode, at least one reference electrode, at least one counter electrode, and a memory storing instructions executable by a processor, the instructions including: applying to the aqueous sample a step of a stimulus voltage comprising a stepped voltage, each step of the stepped voltage having two or more repeating square wave modulations of equal voltage amplitude defining a group; measuring a resultant current output of the stimulus voltage by a measurement comprising square wave voltammetry; and averaging the resultant current output over at least two or more cycles of each of the groups.

[0006] In a further embodiment, a system is provided for measuring components of an aqueous sample using square wave voltammetry, the system comprising: a voltammetric electrode, at least one reference electrode, at least one counter electrode, and a memory device storing code executable by a processor, the code including: code for applying to the aqueous sample a step of a stimulus voltage comprising a stepped voltage, each step of the stepped voltage having two or more repeating square wave modulations of equal voltage amplitude defining a group; code for measuring a resulting composite current output from the stimulus voltage by a measurement comprising square wave voltammetry; and code for averaging the composite current output over at least two or more cycles of each of the groups.

[0007] The foregoing is a summary and, as such, may contain simplifications, generalizations, and omissions of detail. As such, 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, as well as other further features and advantages, reference is made to the following description taken in conjunction with the accompanying drawings, the scope of the invention being set forth in the appended claims. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 shows example simulation results of the effect of AC line interference on square wave voltage measurements when swept from −0.5 V to +0.5 V in 101 ramp steps with fmod=500 Hz and fline=50 Hz. [Diagram 2] Figure 2 shows an example oscilloscope capture image of the stimulus voltage (top) and response current (bottom) of a square wave voltage, where cursors labeled X1 and X2 may span an even number of power line periods. [Diagram 3]Figure 3 shows example oscilloscope capture images of the stimulus voltage (top) and response current (bottom) of a square wave voltage with repeating cycles, where the cursors labeled X1 and X2 may span an even number of power line periods. [Figure 4] FIG. 4 is a block diagram for processing the response for square wave voltammetry with repeated cycles. [Diagram 5] FIG. 5 shows an example of the magnitude response of a uniformly weighted averaging filter of length r=5 centered at frequency fmod=100Hz, showing nulls in the response at DC, fline=60Hz, and the second and third harmonics of fline. [Figure 6A] FIG. 6A illustrates an example of unequal weighting averaging over repeat cycles. [Figure 6B] FIG. 6B illustrates another example of unequal weighting averaging over repeat cycles. [Figure 6C] FIG. 6C illustrates a further example of unequal weighting averaging over repeat cycles. [Figure 7] FIG. 7 shows an example of the magnitude response of uniform and triangular averages of 8 repetitions at fmod=200 Hz. [Figure 8] FIG. 8 shows an example frequency response of 11 repeated sweeps at fmod=150 Hz using a more highly averaged profile. [Figure 9] Figure 9 shows example oscilloscope capture images of five repeated stimulus and response cycles at fmod=100Hz, where the first repeated cycle of each group can be excluded from averaging since the ramp steps are large and unrepresentative. [Figure 10] FIG. 10 is a flow chart for measuring components in an aqueous sample using square wave voltammetry. [Figure 11] FIG. 11 is a diagram illustrating an example of a computer circuit. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] It will be readily understood that the components of the embodiments as generally described and illustrated in the Figures herein could be arranged and designed in a wide variety of different configurations in addition to the example embodiments described. Thus, the following more detailed description of the example embodiments, as represented in the Figures, is not intended to limit the scope of the claimed embodiments, but is merely representative of example embodiments.

[0011] Throughout this specification, the reference to "one embodiment" or "an embodiment" (or similar phrases) means that a particular feature, structure, or characteristic described in connection with that embodiment is included in at least one embodiment. Thus, the appearances of phrases such as "in one embodiment" or "in an embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment.

[0012] Furthermore, the described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. In the following description, numerous specific details are provided to provide a thorough understanding of the embodiments. However, one of ordinary skill in the art will recognize that various embodiments may be practiced without one or more of the specific details, or with other methods, components, materials, etc. In other instances, well-known structures, materials, or operations are not shown or described in detail. The following description is for illustrative purposes only and merely illustrates examples of specific embodiments.

[0013] A variety of voltage waveforms may be used in voltammetry experiments. Many of the commonly used stimulus waveforms involve step changes in voltage. Square-wave voltammetry (SWV) may superimpose a square-wave modulation on top of a voltage ramp. In modern SWV instruments, the "ramp" may consist of a series of small amplitude voltage steps, usually in a staircase pattern. The modulation amplitude is usually tens of millivolts, although lower or higher amplitudes may also be used. The modulation amplitude differs from the amplitude of the ramp step to which it is applied. In SWV, the height of each step may be only a few millivolts. In contrast, step voltammetry (SCV) traverses the voltage range of interest in several larger steps. Instruments performing SWV scans usually capture the current response to the positive- and negative-going portions of the square-wave modulation separately. The latter is usually subtracted from the former to cancel out the "background" response current. Many other stimulus waveforms with step changes are conceivable and may be used.

[0014] Thus, the systems and methods described herein provide a technique for enhancing conventional SWV. This may be referred to as repetitive cycle square wave voltammetry (RCSWV). While this is a preferred embodiment, the ideas described are not limited to SWV and may be applied to any stimulus waveform that includes a series of periodic edge transitions, with the periodicity preferably being selected in relation to the power line frequency. For example, in a laboratory environment, a shielded enclosure may mitigate the problem of power line interference. However, a contradiction arises when applying SWV measurements to heavy industrial and field measurement applications. Challenging venues and locations often do not allow the use of shielded enclosures used in sensitive laboratory work and laboratory environments. As a result, it is necessary to limit the range of available SWV settings to eliminate interference from AC power lines.

[0015] A voltage step can induce a response current that varies over time. At the time of the step, an initial surge of current occurs due to capacitive charging of the double-layer electrochemical capacitor at the electrode-fluid interface. This capacitive charging current decays exponentially. Once the capacitive charging current has disappeared, a second current component becomes dominant. This so-called faradaic current is the result of ion diffusion and its amplitude depends on the applied stimulus voltage compared to the activation potential of the reaction occurring near the electrode-fluid interface. This dependence is the basis on which fluid samples are commonly characterized.

[0016] It should be noted that the faradaic current also varies with time. It reaches a maximum value immediately after the step transition and decays from that initial value to a lower asymptotic value depending on the diffusion rate of the reactants and the size and geometry of the electrodes. Many conventional instruments integrate a portion of this decay curve to report a single value associated with each square wave half-cycle or step.

[0017] Because their differential response currents are small, typically nanoamps to microamps, these measurements are easily contaminated by interference from nearby AC (alternating current) power lines. If the integration scheme of the SCV instrument is known, the instrument settings can be adjusted to make the integration period one or more periods of the power line frequency. For square wave voltammetry, a different strategy may be used. The modulation frequency may be chosen to place the positive and negative half-cycle transitions an integer multiple of the power line period apart. When this is done, the inferential contributions to each will be similar and are removed when subtracted with the half-cycle response. This works regardless of the integration scheme used by the instrument. Experienced users of conventional SWV instruments may choose square wave modulation frequencies to achieve this result.

[0018] The example illustrated embodiments will be best understood with reference to the drawings, in which: The following description is for purposes of illustration only and merely illustrates examples of specific embodiments.

[0019] Figure 1 shows an idealized SWV response plot in one embodiment where the potential effects of power line interference are with and without additive AC noise. In this example, the AC interference shifts the response peak position by 30 mV. If this approach were used to measure a Nernstian pH response, this would result in an error of more than 0.5 in pH.

[0020] In a laboratory environment, careful wiring and the use of shielded enclosures may mitigate the problem of power line interference. In that event, the step rate or square wave modulation frequency may be considered as free parameters that the experimenter can adjust to obtain optimal results. However, a conflict arises when SWV measurements are applied to heavy industrial or field measurement applications. In such difficult locations and positions, careful laboratory practices and the shielded enclosures used in laboratory environments are often hampered. As a result, the range of SWV settings must be severely limited to eliminate interference from AC power lines.

[0021] Selecting a square-wave modulation frequency with a fixed relationship to the frequency of the AC power grid can mitigate the corruption of sensitive SWV measurements by induced power line noise. Similarly, in SCV mode, the length of each acquisition window is ideally equal to a fixed multiple of the AC line period. As a result, the step duration or modulation frequency is no longer a free parameter but is restricted to a set of discrete values. For conventional SWV to reject power line interference, the selected modulation frequency must be half the power line frequency or an integer fraction of it. Higher modulation frequencies cannot be used because they compromise AC line immunity.

[0022] The aforementioned limitations can be troublesome when studying certain types of surface-bound reactions where reactive species are depleted very rapidly. A knowledgeable and skilled laboratory analyst can program a potentiostat with a modulation frequency fast enough to measure the current response before it decays. However, the presence of power line-related interference makes this impossible to do without compromising the integrity of the measurement.

[0023] In repeating cycle square wave voltammetry, each single cycle of a conventional SWV voltage excitation is replaced by a shorter cycle divided by an integer number r such that the total time of these repeating cycles is equal to the duration of the original single cycle, ideally the period of an even number k of power line periods. This is illustrated in Figures 2 and 3. The top oscilloscope waveform in Figure 2 shows the stimulus waveform of a conventional SWV measurement in one embodiment, and the top waveform in Figure 3 shows the corresponding RCSWV waveform of the present disclosure. Comparing the time cursors X1 and X2, it can be seen that a single square wave cycle of conventional SWV is replaced by several shorter square wave cycles in repeating cycle SWV. The time interval bounded by X1 and X2 is preferably selected to ensure the elimination of AC lines.

[0024] In a preferred embodiment, the square wave frequency and the power line frequency are related by the equation shown in Equation 1.

[0025]

number

[0026] In this formula, fmod is the square wave modulation frequency, fline is the local power line frequency (usually 50Hz or 60Hz), r is the number of square wave repetitions per lamp voltage value, and k is an integer multiple of the power line period into which these repetitions fall exactly. Power line frequencies vary between regions or countries, and parameters may be adjusted for local use.

[0027] In one embodiment, the current response reported for each of the stimulus ramp voltages is obtained by averaging the constituent square wave responses. This averaging can be performed either before or after the SWV differencing operation. In one embodiment, the periodic responses are combined with uniform weighting, although other embodiments may employ averaging with non-uniform weighting.

[0028] The option to perform non-uniform averaging of responses over each group of repeating square wave cycles is a novel and useful aspect of the present disclosure: it provides an additional degree of freedom in measurement setup that a skilled instrument designer or analyst can use to improve measurement robustness.

[0029] A diagram illustrating the operations involved in one embodiment is shown in Figure 4. This is depicted as a discrete-time digital signal processing (DSP) block diagram familiar to DSP implementers. The numerical flow shown comprises separate paths for the positive and negative half-cycle responses to each square wave, with each path incorporating the same averaging calculation. Those skilled in the art will recognize that other processing diagrams within the scope of this disclosure may be used to achieve the same numerical results.

[0030] The averaging block of FIG. 4 operates on discrete-time data and may be considered as a finite impulse response (FIR) style digital filter. In many embodiments, the filter weights are selected to produce a "low-pass" frequency response. A subsequent difference operation has the effect of interleaving both sets of filter coefficients with inverted sign. The resulting aggregate filter has twice the sample rate and a "high-pass" frequency response, with its passband centered on the modulation frequency fmod. This ensures that the "background" current (averaged over the positive and negative half cycles) is completely rejected while passing the desired differential current. Furthermore, by careful selection of the filter length (number of iterations) and weighting coefficients, a frequency response "null" can be achieved that suppresses interference occurring at the AC line frequency fline.

[0031] In FIG. 5, the amplitude response obtained from a pair of averaging filters of length 5 and uniform weighting in one embodiment is shown. The horizontal axis is frequency in Hertz (Hz). When operating at fmod=100Hz, the filter shows nulls at 60Hz, 120Hz, and 180Hz, eliminating the first three harmonics at fline=60Hz. The desired differential response signal at fmod is marked with a "*" and the AC line fundamental (shown with non-zero amplitude only for clarity) is marked with an "x". This example shows that even the very simple case of a repeating cycle SWV is superior to conventional SWV measurements. For conventional SWV, the choice of fmod=100Hz is not permitted in the United States because it does not provide immunity to pollution from AC power lines. The maximum allowable modulation frequency for conventional SWV is fmod=30Hz in the United States. More generally, it is half the local AC power frequency. In contrast, users of repeated cycle SWVs can employ very high modulation frequencies and still maintain power line immunity by using an appropriate number of repeated cycles.

[0032] Non-uniform weighted averaging of the repeating square wave response provides further advantages, as demonstrated by several examples. In one embodiment, possible weighting shapes are shown in Figures 6A, 6B, and 6C for measurements using 31 repeating cycles. The triangular weighting shown in the graph above provides the advantage of being easier to explain than uniform weighting. The amplitude plot in Figure 5 is recognizable to those skilled in the art as having a sin(f) / f or "sinc" characteristic with equally spaced nulls between side lobes whose peaks decrease linearly on either side of the main lobe. In a preferred embodiment, fmod and r can be selected to place one of the nulls at fline. As the number of repeats increases, the nulls occur closer together and they also become narrower. Eventually, the nulls may become so narrow that even normal variations in the power line frequency may not completely eliminate the power line interference. To address this issue, triangular weighted averaging can be used. Figure 7 compares the effects of triangular averaging and uniform averaging for 8 repeating cycles at fmod=200Hz. The amplitudes are plotted in decibels because the differences are more easily seen using a logarithmic axis. It is clear that with triangular weighting there are fewer nulls, but the nulls are wider. This triangular setup with wide notches at 50Hz, 100Hz, and 150Hz is suitable for use in any country with a nominal power line frequency of 50Hz, and maintains at least 60dB of line rejection even with a 1.5% power line frequency error, and greater than 50dB of line rejection even with a 5% error.

[0033] FIG. 8 shows the effect of a weighting function similar to the example of FIG. 6B, but with 11 repeat cycles, in one embodiment. When used with a modulation frequency of 150 Hz, these weights provide a perfect null at 50 Hz and over 72 dB of attenuation at 60 Hz, allowing this measurement protocol to be used in both the US and the UK. The design of averaging weights to meet specific criteria can be performed by FIR (Finite Impulse Response) filter design, so the exact weights used in this example can be adjusted. Any set of weighting coefficients and how they are derived is within the scope of this disclosure.

[0034] In one embodiment, the voltage change between the ramp steps is significantly larger than the square wave amplitude in the oscilloscope captured image as shown in FIG. 9. Note that the first current response in each repeat group is not typical and is much larger than the others. If the repeats of each group are averaged, the response from the first repeat may be overweighted and the resulting filter response may differ from the intended one. Therefore, another aspect of the present disclosure is to allow the first repeat in each group to be excluded from the averaging calculation. If this is done in the case of FIG. 9, only the last four repeat cycles from each group will be averaged and the resulting frequency response will be the same as in the case of FIG. 5. To achieve this result, the instrument may provide an explicit "skip first" option. Also, a similar result can be achieved by setting the first weighting factor to zero.

[0035] In one embodiment according to FIG. 10, the measurement of an analyte of a sample is possible. The analyte can be any ion, component, or feature of the sample. In step 1001, in one embodiment, an aqueous sample can be introduced into a sample chamber or region. The aqueous sample can be placed or introduced into the sample chamber manually by a user or using mechanical means, such as gravity flow, pumps, pressure, fluid flow, etc. For example, the aqueous 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 performed. In one embodiment, valves, etc., can be present to control the inflow and outflow of the aqueous solution into and from one or more chambers. Once the sample is introduced into the measurement system, the system can measure the analyte or property of the sample.

[0036] In step 1002, in one embodiment, the system and method can apply a step of the stimulation voltage to the aqueous sample, including a step voltage, where each step of the step voltage defines a group and includes two or more repeating square wave modulations of equal or similar voltage amplitude. In step 1003, in one embodiment, the system and method can measure the resultant current output resulting from the stimulation voltage, where the measurement includes square wave voltammetry. In step 1004, in one embodiment, the system and method can average the resultant current output over at least two or more cycles of each group. Further details and structures related to this step are described herein.

[0037] The combination of the width of the step shape and the additional square wave modulation defines the complete excitation voltage waveform and may be referred to as an electrical signal. The electrical signal may be applied using one or more electrodes, for example, a series of electrodes. The electrodes may include a working electrode, a counter (auxiliary) electrode, a reference electrode, etc. In one embodiment, the electrodes may include pH-sensitive voltammetric electrodes. In one embodiment, the one or more series of electrodes may be boron-doped diamond (BDD) electrodes. Other electrode materials are also disclosed and contemplated. Electrodes of carbon-based or metallic materials (e.g., silver, gold, mercury, nickel, etc.) may eventually oxidize themselves, thereby generating interfering signals and contributing to errors in measurements. The use of BDD may serve as a better electrode material than these materials. One or more electrodes may be operably coupled to the electrical circuitry and / or any square wave voltammetry circuitry described herein. Such circuitry may allow for the delivery of voltage protocols, receiving current responses, collecting, filtering, weighting, averaging, storing, outputting, etc. of data.

[0038] In one embodiment, the electrodes may be disposed completely or at least partially within the volume of the aqueous solution or sample. For example, when 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, one or more electrodes may be partially disposed within the chamber, with other portions of the electrodes disposed outside the chamber. Thus, when the aqueous solution is introduced into the chamber, the aqueous solution covers only the portions of the electrodes disposed within the chamber.

[0039] The methods and systems may determine the analyte, analyte concentration, or property of the sample in step 1005. This determination may be performed based on the previous voltage step and the resultant current from the method or system.

[0040] However, when an analyte or property can be determined in step 1005, the system can output the properties of the aqueous sample, the ion concentration of the analyte, etc., in step 1006. In an embodiment, the output can be in the form of a display, storing the data in a memory device, transmitting the output by a connected or wireless system, printing the output, etc. The system can be automated such that the system can automatically output the results. The system can also have associated alarms, limits, or predefined thresholds. For example, when a measurement reaches a threshold, the system can respond by raising an alarm, alerting the system / personnel of a fault, altering the flow of the aqueous solution, etc. The data can be analyzed in real time, stored for later use, or a combination thereof.

[0041] In one embodiment, the step voltage may be controlled in real time by the processor. In one embodiment, the square wave modulation amplitude may be preset. In one embodiment, the timing of each cycle may be controlled by a "hardware state machine" rather than each edge being directly controlled by the processor. Alternatively, some or all of the processing may be performed using dedicated logic circuits including hardware state machines. These parameters may be controlled by a user, a configuration program, a circuit, a processor, etc. In one embodiment, the primary interfaces between the processor and components may be I2C, SPI, and RS-485, in addition to other hardware disclosed. These may be local serial buses and / or serial field buses used between the measurement instrument and an external computer, and they may include USB support.

[0042] Thus, various embodiments described herein provide technical improvements over conventional methods and instruments of square wave voltammetry. Using the techniques described herein, in one embodiment, methods and apparatus for instruments for measuring analytes using square wave voltammetry may be used. This is in contrast to conventional methods that have the aforementioned limitations. Such techniques provide better construction methods and instruments for measuring analytes using square wave voltammetry.

[0043] While various other circuits, circuitry, or components may be utilized in an information processing device, an example is illustrated in FIG. 11 for an apparatus for measuring an analyte using square wave voltammetry according to any of the various embodiments described herein. The device circuitry 10' may include, for example, a measurement system on a chip design found in a particular computing platform (e.g., mobile computing, desktop computing, etc.). The software and processor are integrated into a single chip 11'. The processor includes an internal arithmetic unit, registers, cache memory, buses, I / O ports, etc., as is well known in the art. Essentially all peripherals (12') may be connected to the single chip 11', although the internal buses, etc., are vendor dependent. The circuitry 10' integrates the processor, memory control, and I / O controller hub all into the single chip 11'. Also, SATA, PCI, and LPC are not typically used in this type of system 10'. Common interfaces include, for example, SDIO and I2C.

[0044] A power management chip 13', such as a battery management unit BMU, manages the power provided, for example via a rechargeable battery 14', which can be recharged by connecting to a power source (not shown). In at least one design, a single chip, such as 11', is used to provide BIOS-like functionality and DRAM memory.

[0045] The system 10' typically includes one or more of a WWAN transceiver 15' and a WLAN transceiver 16' to connect to various networks, such as telecommunication networks and wireless Internet devices (e.g., access points). Additionally, the system 10' typically includes devices 12', such as, for example, transmit and receive antennas, oscillators, PLLs, etc. The system 10' includes an input / output device 17' for data input and display / rendering (e.g., a computing location remote from the single beam system that is easily accessible to a user). The system 10' also typically includes various memory devices, such as, for example, flash memory 18' and SDRAM 19'.

[0046] The electronic components of one or more systems or devices may include at least one processing unit, a memory, and a communication bus or means coupling various components including the memory to the processing unit, but not limited thereto, as can be seen from the above description. The system or device may include or have access to various device-readable media. The system memory may include device-readable storage media in the form of non-volatile and / or volatile memory, such as read-only memory (ROM) and / or random access memory (RAM). By way of example and 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 one embodiment of an instrument for square wave voltammetry.

[0047] As will be appreciated by those skilled in the art, various aspects may be embodied as a system, method, or apparatus program product. As such, the aspects may take the form of an entirely hardware embodiment or an embodiment including software, all of which may be generally referred to herein as a "circuit," "module," or "system." Additionally, the aspects may be embodied in the form of an apparatus program product, in one or more device-readable mediums having device-readable program code embodied therein.

[0048] It should be noted that various functions described herein may be implemented using instructions stored on a device-readable storage medium, such as a non-signal storage device, and those instructions are executed by a processor. In the context of this specification, a storage device is not a signal, and "non-transitory" includes all media other than signal media.

[0049] The program code that performs the operations may be written in any combination of one or more programming languages. The program code may run entirely on a single device, partially on a single device, as a stand-alone software package, partially on a single device and partially on another device, or entirely on other devices. In some forms, the devices may be connected via any manner of connection or network, including a local area network (LAN) or a wide area network (WAN), or the connection may be effected via another device (e.g., via the Internet using an Internet Service Provider), via a wireless connection such as near field communication, or via a hardwired connection such as via a USB connection.

[0050] Example embodiments are described herein with reference to figures illustrating methods, apparatus, and products according to various example embodiments. It will be understood that operations and functions may be implemented, at least in part, by program instructions. These program instructions may be provided to a processor of an apparatus, such as a measurement apparatus as shown in FIG. 11, or other programmable data processing apparatus to create a machine, such that the instructions executed via the apparatus's processor implement the specified functions / operations.

[0051] It should be noted that values ​​provided herein should be construed to include equivalent values ​​as indicated by the use of the term "about." Equivalent values, as would be apparent to one of ordinary skill in the art, include at least values ​​obtained by ordinary rounding of the last significant figure.

[0052] The present disclosure has been presented for purposes of illustration and description, and is not intended to be exhaustive or limiting. Many modifications and variations will be apparent to those skilled in the art. The illustrated embodiments have been selected and described in order to explain the principles and practical applications, and to enable others skilled in the art to appreciate the disclosure of various embodiments with various modifications as appropriate for the particular use envisioned.

[0053] Thus, while illustrative 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 made by those skilled in the art without departing from the scope or spirit of the present disclosure.

Claims

1. 1. A method for measuring components of an aqueous sample using square wave voltammetry, comprising: introducing the aqueous sample into a chamber of a square wave voltammetry apparatus; applying a step of a stimulation voltage to the aqueous sample, the step comprising a staircase voltage, each step of the staircase voltage having two or more repeating square wave modulations defining a group and of equal voltage amplitude; measuring a resultant current output resulting from said stimulation voltages using a measurement comprising said square wave voltammetry; and each of said groups averaging said composite current output over at least two or more cycles.

2. The method of claim 1 , wherein the averaging step comprises uniform weighting of each of the groups.

3. The method of claim 1 , wherein the averaging step includes unequal weighting of each of the groups.

4. The method of claim 3 , wherein the averaging step further comprises selecting the non-uniform weighting to achieve a desired frequency response.

5. The method of claim 4 , wherein the desired frequency response includes nulls positioned to remove interfering frequencies.

6. The method of claim 5 , wherein the interference frequency comprises interference from an AC power source.

7. The method of claim 1 , wherein the length of the cycle averaged over the modulation group is equal to an integer multiple of the length of the power supply period.

8. The method of claim 3 , wherein the non-uniform weighting comprises triangular weighting.

9. The method of claim 1 , wherein the average of the resultant current output plotted against excitation voltage correlates to an analyte in the aqueous sample.

10. The method of claim 1 , wherein the average of the composite current output measured at one or more particular excitation voltages correlates to an analyte in the aqueous sample.

11. 1. An apparatus for measuring components of an aqueous sample using square wave voltammetry, comprising: A voltammetric electrode; At least one reference electrode; At least one counter electrode; a memory for storing instructions executable by a processor; The instruction: instructions to apply a step of a stimulation voltage to the aqueous sample, the step comprising a staircase voltage, each step of the staircase voltage defining a group and having two or more repeating square wave modulations of equal voltage amplitude; instructions for measuring a resultant current output resulting from said stimulation voltages by said measurement comprising square wave voltammetry; and instructions for averaging the composite current output over at least two or more cycles of each of the groups.

12. The apparatus of claim 11 , wherein the averaging instructions include a uniform weighting of each of the groups.

13. The apparatus of claim 11 , wherein the averaging instructions include unequal weighting of each of the groups.

14. The apparatus of claim 13 , wherein the instructions to average further comprise instructions to select the non-uniform weighting to achieve a desired frequency response.

15. The apparatus of claim 14 , wherein the desired frequency response includes nulls positioned to remove interfering frequencies.

16. The apparatus of claim 15 , wherein the interference frequency comprises interference from an AC power source.

17. The apparatus of claim 11 , wherein a length of a cycle averaged over a modulation group is equal to an integer multiple of a power supply period.

18. The apparatus of claim 13 , wherein the non-uniform weighting comprises triangular weighting.

19. 16. The apparatus of claim 15, wherein the average of the resultant current output plotted against excitation voltage correlates to an analyte in the aqueous sample.

20. 1. A system for measuring components of an aqueous sample using square wave voltammetry, comprising: The system comprises: A voltammetric electrode; At least one reference electrode; At least one counter electrode; a memory device for storing code executable by the processor; The code is code for applying a step of a stimulation voltage to the aqueous sample, the step comprising a staircase voltage, each step of the staircase voltage defining a group and having two or more repeating square wave modulations of equal voltage amplitude; code for measuring a resultant current output resulting from said stimulation voltages, the measurement comprising square wave voltammetry; and code for averaging the resultant current output over at least two or more cycles of each of the groups.

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