Manganese detection

Abstract

One embodiment of a method for measuring the amount of manganese in an aqueous sample includes reducing with a dechlorinating agent, wherein the dechlorinating agent comprises iron (II) and potassium iodide; oxidizing Mn(II) to Mn(IV) in the aqueous sample under alkaline conditions using sodium hydroxide, chelating Fe(II) and Fe(III) in the aqueous sample using hydroxyethylidene diphosphonic acid (HEDP), oxidizing an amount of a colorimetric indicator, 3,3',5,5'-tetramethylbenzidine (TMB) with Mn(IV); and measuring the amount of manganese in the aqueous sample by measuring the absorbance intensity of the oxidized amount of 3,3',5,5'-tetramethylbenzidine (TMB) at a certain wavelength. Other aspects are described and claimed.

Description

[0001] Cross-reference to related applications

[0002] This application claims priority to U.S. Patent Application Serial No. 63 / 239,147 entitled “Manganese Measurement”, filed August 31, 2021, the contents of which are incorporated herein by reference. Background Technology

[0003] This application generally relates to the measurement of manganese in aqueous or liquid samples, and more specifically to the measurement of manganese using iron and potassium iodide to reduce chlorine interference from samples containing free chlorine or monochloramine.

[0004] Ensuring water quality is crucial in many industries, such as pharmaceuticals and other manufacturing sectors. Furthermore, ensuring water quality is essential for the health and well-being of humans, animals, and plants that depend on water for survival. One component commonly measured in water is manganese. Excessive manganese in water can be harmful to humans or animals. Therefore, detecting the presence and concentration of manganese in water or other liquid solutions is of paramount importance. Summary of the Invention

[0005] In summary, one embodiment provides a method for measuring the amount of manganese in an aqueous sample, the method comprising: reducing the sample using a dechlorinating agent comprising Fe(II) and potassium iodide; oxidizing Mn(II) in the aqueous sample to Mn(IV) under alkaline conditions using sodium hydroxide, and chelating Fe(II) and Fe(III) in the aqueous sample using hydroxyethyl phosphate (HEDP), oxidizing a certain amount of 3,3',5,5'-tetramethylbenzidine (TMB) with Mn(IV); and measuring the amount of manganese in the aqueous sample by measuring the absorbance intensity of the oxidized certain amount of 3,3',5,5'-tetramethylbenzidine (TMB) at a wavelength using a colorimetric indicator.

[0006] One embodiment provides an apparatus for measuring the amount of manganese in an aqueous sample, the apparatus comprising: a measuring chamber; and a memory device storing processor-executable instructions for: measuring the amount of manganese in the aqueous sample by measuring the absorbance intensity at a certain wavelength of an oxidized amount of 3,3',5,5'-tetramethylbenzidine (TMB) using a colorimetric indicator, wherein the aqueous sample is reduced using a dechlorinating agent comprising Fe(II) and potassium iodide, wherein Mn(II) in the aqueous sample is oxidized to Mn(IV) under alkaline conditions using sodium hydroxide, and wherein hydroxyethyl phosphate (HEDP) chelates Fe(II) and Fe(III) in the aqueous sample.

[0007] Another embodiment provides a method for measuring the amount of manganese in an aqueous sample, the method comprising: introducing a certain amount of 3,3',5,5'-tetramethylbenzidine (TMB) into the aqueous sample, wherein Mn(IV) oxidizes the certain amount of 3,3',5,5'-tetramethylbenzidine (TMB); and measuring the amount of manganese in the aqueous sample by measuring the absorbance intensity of the oxidized certain amount of 3,3',5,5'-tetramethylbenzidine (TMB) at a certain wavelength using a colorimetric indicator.

[0008] The foregoing is an overview and may therefore contain simplifications, generalizations and omissions of details; therefore, those skilled in the art will understand that this overview is merely illustrative and is not intended to be limiting in any way.

[0009] To better understand the implementation schemes and their other and additional features and advantages, refer to the following description in conjunction with the accompanying drawings. Attached Figure Description

[0010] Figure 1 A flowchart of an exemplary manganese measurement system is shown.

[0011] Figure 2 A reaction scheme for detecting manganese is shown.

[0012] Figure 3 An exemplary manganese calibration with different background matrices is shown.

[0013] Figure 4 Exemplary manganese calibrations with different background matrices are shown in tabular form.

[0014] Figure 5 An exemplary tetramethylbenzidine substance is shown in one embodiment.

[0015] Figure 6 An example of a computer circuit system is shown. Detailed Implementation

[0016] It will be readily understood that, in addition to the exemplary embodiments described herein, the components of the embodiments summarized and illustrated in the accompanying drawings can 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.

[0017] Throughout this specification, the reference to "one embodiment" or "an embodiment" (etc.) means that a particular feature, structure, or characteristic described with respect to that embodiment is included in at least one embodiment. Therefore, the phrases "one embodiment" or "in an embodiment," etc., appearing in various places throughout this specification, do not necessarily refer to the same embodiment.

[0018] Furthermore, the described features, structures, or characteristics can be combined in any suitable manner in one or more embodiments. Numerous specific details are provided in the following description to give a comprehensive understanding of the embodiments. However, those skilled in the art will recognize that various embodiments can be implemented without one or more specific details, or using 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 illustrates only certain exemplary embodiments.

[0019] Conventional methods for measuring manganese in water or aqueous samples may have some limitations. For example, manganese measurement can be used to determine water quality. High concentrations of manganese can be harmful to animals, humans, and / or plants. For instance, elevated manganese levels may be associated with neurological and behavioral effects such as deficits in memory, attention, and motor skills. As another example, a user or entity may want the manganese level in water to be below a specific threshold; therefore, the user can measure manganese to determine whether the amount of manganese is below said threshold.

[0020] Previous methods for measuring manganese have limitations. For example, some methods are unavailable or unapproved in certain geographic areas. Some manganese tests require the use of cyanide. The reagents used in some tests may be unapproved or regulated, making the test unusable due to environmental, regulatory, and / or government guidelines. Tests that use more environmentally friendly reagents and can measure manganese in the presence of chlorine interfering substances can provide a solution to this problem.

[0021] Conventional manganese measurement methods can be affected by interfering substances in the sample, leading to inaccurate manganese measurement results. An exemplary interfering substance may include chlorine or chlorine-containing substances. An example of a manganese test that is intolerant to chlorine-containing samples is the LCW 632 manganese test (Hach Company, Loveland, CO). This test lacks a dechlorination step. Such tests, and similar tests, cannot measure manganese in the presence of chlorine or chlorine-containing substances.

[0022] A method is needed to accurately measure manganese in the presence of chlorine or chlorine-containing substances.

[0023] Therefore, one embodiment provides a system and method for measuring manganese in an aqueous solution or an aqueous sample. In one embodiment, the aqueous sample containing a certain amount of manganese may also contain chlorine and / or chlorinated substances. In one embodiment, the aqueous sample may be reduced using a dechlorinating agent. The dechlorinating agent may contain iron(II) and potassium iodide. In one embodiment, an iron(II) standard may be oxidized by chlorine or chlorinated substances in the aqueous sample. The concentration of the iron sample may be 100 mg / L. The iron in the iron standard may be in an acid (e.g., 0.85% hydrochloric acid). In one embodiment, unreacted iron(II) may be removed by chelation or oxidation to iron(III) followed by chelation. Chelation may be performed using hydroxyethyl phosphate (HEDP). Under alkaline conditions using sodium hydroxide, Mn(II) may be oxidized to Mn(IV). Mn(IV) may oxidize a certain amount of 3,3',5,5'-tetramethylbenzidine (TMB). In one embodiment, a colorimetric technique may be used to measure the amount of manganese in the aqueous sample by measuring the absorbance intensity of the oxidized TMB fraction. Test samples can be compared with blank measurements. Absorbance can be measured at approximately 450 nanometers (nm). Colorimetric measurements can be performed using a spectrophotometer.

[0024] The exemplary embodiments illustrated will be best understood by referring to the accompanying drawings. The following description is for illustrative purposes only and illustrates only some exemplary embodiments.

[0025] Reference Figure 1 Exemplary systems and methods for detecting manganese in aqueous samples are shown. In one embodiment, an aqueous sample containing manganese may be introduced into a reaction vessel. The reaction vessel may be used to complete method steps prior to transfer to a colorimetric container or cuvette. In one embodiment, the reaction vessel may serve as a colorimetric container. The amount of manganese in the aqueous sample may be determined by the change in absorbance of a colorimetric indicator. The measurement of the absorbance of the aqueous sample containing a certain amount of manganese is compared with a blank measurement.

[0026] Aqueous samples can include samples from natural water bodies, containment tanks, processing tanks, pipes, etc. The solution can be in a continuous flow state, a static volume of liquid, or any combination thereof. In one embodiment, the solution can be introduced into the reaction chamber and / or test chamber of the measuring device. In one embodiment, the measuring device can be a benchtop device, a field device, or a handheld device. Handheld devices can have advantages such as lower cost, portability, and field use. Introducing the sample into the measuring device can include the user manually or using mechanical means (e.g., gravity flow, pump, pressure, fluid flow, etc.) to place or introduce the sample into the test chamber. For example, a pump can be used to introduce an aqueous sample for manganese measurement into the measuring chamber or test chamber. In one embodiment, valves, etc., can control the flow of the solution into or out of one or more chambers (if present).

[0027] Chambers, containers, and units can hold aqueous samples and related reagents, such as iron standards, oxidants, buffers, chelating agents, acids, and alkalis. Various reagents can be added to the aqueous sample in powder, liquid, or pre-packaged modules. The device may include one or more reagent bottles containing the necessary reagents. The reagents contained in the one or more bottles can be pumped or gravity-fed. The flow of reagents can be metered to ensure the appropriate volume delivered to the measuring unit. Aqueous samples can be fed through pressurized inlets, containers, etc. Aqueous samples can be introduced into the measuring chamber by pumping or gravity feeding. The sampling device can be connected in series or parallel with the aqueous flow. The device may have a system to ensure proper mixing of the aqueous sample and reagents.

[0028] Alternatively or additionally, the measuring device may be present in or introduced into a volume of solution. The measuring device can then be exposed to that volume of aqueous sample, where it can be measured. The method and system can measure a sample taken from a volume of liquid, or it may be a stopped flow design. Alternatively, the system may be a flow system in which aqueous samples and / or reagents are automatically mixed and measured. As discussed in more detail herein, once the sample comes into contact with the measuring system, the system can measure the amount of manganese in the sample. In one embodiment, the measuring device may include one or more chambers in which one or more method steps can be performed.

[0029] At point 101, in one embodiment, an iron standard and potassium iodide, or a dechlorinating agent, may be introduced into the aqueous sample. The aqueous sample may contain a certain amount of manganese. The aqueous sample may contain interfering substances. Interfering substances may be chlorine, chlorinated substances, or combinations thereof. In one embodiment, the dechlorinating agent may contain iron at a concentration of 100 mg / L. The iron may be in dilute hydrochloric acid. As an example, the acid may be 0.85% dilute hydrochloric acid. In one embodiment, potassium iodide (KI) may be added together with the dechlorinating agent. The iron standard may be added in a reaction vessel or a measuring vessel.

[0030] At point 102, in one embodiment, a certain amount of manganese (Mn) in the aqueous sample can be oxidized. Oxidation can oxidize Mn(II) to Mn(IV). Oxidation can be carried out under alkaline conditions using sodium hydroxide. In one embodiment, unreacted iron can be removed from the aqueous sample by chelation. Unreacted iron can be in the form of iron(II) and is present in the incompletely oxidized aqueous sample from the start of the addition of the dechlorinating agent. Iron(II) can be oxidized to iron(III). Unreacted iron can also be chelated. In one embodiment, any unreacted iron(II) in the solution can be oxidized to iron(III) and chelated using hydroxyethyl phosphate (HEDP). In one embodiment, Fe(II) and Fe(III) can be completely chelated. HEDP can be added to the aqueous sample in an alkaline or strongly alkaline solution. The alkaline solution can be sodium hydroxide (NaOH). The addition of hydroxyethyl phosphate can be in a reaction vessel or a measuring vessel.

[0031] At point 103, in one embodiment, a colorimetric indicator may be added to an aqueous sample containing a certain amount of manganese. In one embodiment, the colorimetric indicator may be tetramethylbenzidine or 3,3',5,5'-tetramethylbenzidine (TMB). An example of TMB and oxidized TMB (at a pH below 1) is provided. Figure 5 As shown in the diagram. In one embodiment, the aqueous sample can be acidified using hydrochloric acid (HCl), phosphoric acid (H3PO4), etc. In one embodiment, the method may be referred to as a three-step process, wherein the steps include the addition of a dechlorinating agent, the addition of hydroxyethyl phosphoric acid in an alkaline solution, and the addition of TMB. An exemplary reaction scheme of the method is shown in... Figure 2 The steps are shown in the diagram. The timing of the steps can be varied. However, as an example, the dealumination step can take two minutes. Hydroxyethyl phosphoric acid can be present for five minutes before the next step of adding the colorimetric indicator, and then the absorbance is measured for two minutes. This example illustrates a three-step method for measuring the amount of manganese by measuring the absorbance of oxidized TMB at 450 nm.

[0032] In one embodiment, a colorimetric indicator can be added to an aqueous sample. In one embodiment, the colorimetric indicator can provide a measurable parameter, such as absorbance intensity, for the amount of manganese in the aqueous sample. For example, TMB can be oxidized to produce a change in absorbance. For example, the absorbance intensity of the sample can be measured at 450 nm. In one embodiment, the colorimetric indicator can be added after the oxidation and chelation of iron. The colorimetric indicator can be contained in a liquid, powder, or powder pillow. Other methods for introducing colorimetric indicators are considered and disclosed. For example, the reagent can be added using drip irrigation, pipettes, controlled flow systems, as a solid, etc. Specific examples are, for instance, embodiments.

[0033] At 104, in one embodiment, the system and method can determine whether the amount of manganese in an aqueous sample can be measured. In one embodiment, the presence of a certain amount of manganese in the aqueous sample can cause an increase in the absorbance intensity of a colorimetric indicator. In one embodiment, the colorimetric indicator can be reactive to manganese. Examples of this increase in absorbance intensity of the colorimetric indicator and its dose-response curve can be found in... Figure 3 The diagram shows samples with background matrices of deionized (DI) water, samples with free chlorine, and samples with monochloramine. Exemplary data in tabular form regarding the background matrices of deionized (DI) water, samples with free chlorine, and samples with monochloramine are shown in [the diagram]. Figure 4 As shown in the example, the average absorbance at 450 nm increases with increasing amount of manganese in the sample.

[0034] Therefore, the absorbance intensity of a manganese-containing aqueous sample can be correlated with the concentration of manganese in the sample. Absorbance curves can be generated for various manganese concentrations, different colorimetric indicators, and different conditions that may affect absorption (e.g., temperature, sample content, turbidity, viscosity, measuring equipment, aqueous sample chamber, etc.).

[0035] Alternatively or concurrently, manganese concentration measurements can be performed at user-defined periodic intervals or at pre-programmed frequencies within the device. Measuring manganese via the device allows for real-time data acquisition with minimal human intervention. Programmed calibration curves can be input into the device for calibration. In one embodiment, a periodic testing system and method using known amounts of manganese in the sample can be used. The system can then be recalibrated or an error report sent for maintenance. The system can implement cleaning cycles in cases where errors are caused by uncleaned equipment or where cleaning is required. Cleaning of the colorimetric chamber may be necessary at unspecified time intervals, after a certain number of measurements, or upon user or system request. In one embodiment, cleaning cycles for the colorimetric device can be performed using automated or manual methods.

[0036] In one implementation, colorimetric techniques can measure the concentration or amount of manganese using colorimetric indicators or complexes. For example, the measurement could be the measurement of the absorbance of a colored complex at a specific wavelength. The measurement could include obtaining the ratio of absorbance collected at multiple wavelengths. Various measuring devices can be used to perform the measurement, such as portable spectrophotometers (e.g., the DR1900, available from Hach Company, Loveland, CO), test strips, colorimetric analyzers, spectrophotometers, pocket colorimeters, online processing instruments, etc.

[0037] Cuvettes, chambers, containers, units, etc., can hold aqueous samples, at least one colorimetric indicator, and related reagents such as buffers and / or additives. The apparatus may include one or more reagent bottles containing the necessary reagents. The reagents contained in the one or more bottles can be pumped or gravity-fed. The flow of reagents can be metered to ensure the appropriate volume delivered to the measuring unit. Aqueous samples can be fed through pressurized inlets, containers, etc. Aqueous samples can be introduced into the measuring chamber by pumping or gravity feeding. Sampling devices can be connected in series or parallel with the aqueous flow. The apparatus may have a system to ensure proper mixing of the aqueous sample, colorimetric indicator, and related reagents.

[0038] Absorbance intensity or manganese concentration can be output in the form of display, printing, storage, audio, haptic feedback, etc., on the device. Alternatively, the output can be transmitted to another device via wired, wireless, fiber optic, Bluetooth®, near-field communication, etc. One implementation may use an alarm to warn of measurements or concentrations outside acceptable levels. One implementation may use the system to shut off water output or divert water from sources with unacceptable manganese levels. For example, the manganese measuring device may use a relay connected to an electric valve.

[0039] At point 105, in one implementation, if the amount of manganese cannot be determined, the system can continue measuring manganese. For example, the system and method can attempt another measurement on a sample of the same volume containing water, or obtain a new sample. Alternatively or additionally, the system can output alarms, record events, etc.

[0040] At point 106, in one implementation, if the amount of manganese can be determined, the system can provide a measurement result of the manganese concentration. The system can connect to a communication network. The system can issue an alarm to the user or the network. This alarm can be issued regardless of whether the amount of manganese has been determined. The alarm can take the form of sound, visual, data, storing data in a memory device, sending output via a connected system or wireless system, printout, etc. The system can record information such as measurement location, calibration action, geographic location, time, date, number of measurement cycles, etc. Alarms or logs can be automated, meaning the system can automatically output whether calibration is needed. The system can also have associated alarms, limits, or predetermined thresholds. For example, if the amount of manganese concentration reaches a threshold. Alarms or logs can be analyzed in real time, stored for later use, or any combination thereof.

[0041] Therefore, the embodiments described herein represent a technical improvement over conventional manganese measurement techniques. Using the techniques described herein, one embodiment can be used to determine the amount of manganese in an aqueous sample. This contrasts with conventional methods that have the limitations described above. Such techniques provide a faster and more accurate method for measuring manganese in aqueous or liquid solutions.

[0042] Although various other circuits, circuit systems, or components may be used in information processing devices, regarding the instrument for manganese measurement according to any of the embodiments described herein, Figure 6 An example is shown. System 10' may include a measurement system based on chip design results, such as a specific computing platform (e.g., mobile computing, desktop computing, etc.). Software and one or more processors are combined in software + processor 11'. As is well known in the art, a processor includes an internal arithmetic unit, registers, cache memory, buses, I / O ports, etc. The internal buses, etc., vary depending on the vendor, but essentially all other devices (12') can be connected to software + processor 11'. Circuit system 10' combines the processor, memory control, and I / O controller hub into software + processor 11'. Additionally, this type of system 10' generally does not use SATA, PCI, or LPC. For example, common interfaces include SDIO and I2C.

[0043] There are one or more power management chips 13', such as a battery management unit (BMU), which manages power supplied, for example, through a rechargeable battery 14' (which can be recharged by connecting to a power source (not shown). In at least one design, software plus a processor, such as 11', is used to provide BIOS-like functionality and DRAM memory.

[0044] System 10' typically includes one or more of a WWAN transceiver 15' and a WLAN transceiver 16' for connecting various networks, such as radio communication networks and wireless internet devices (e.g., access points). Additionally, it typically includes other devices 12', such as transmitting and receiving antennas, oscillators, PLLs, etc. System 10' includes input / output devices 17' for data input and display / rendering (e.g., a computational location easily accessible to the user, remote from the single-beam system setup). System 10' typically also includes various memory devices, such as flash memory 18' and SDRAM 19'.

[0045] As can be understood from the foregoing, 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 the various components (including the memory) to the one or more processing units. The system or device may include or access various device-readable media. 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)). For example, but not as a limitation, system memory may also include an operating system, application programs, other program modules, and program data. In one embodiment, the disclosed system can be used to measure manganese in an aqueous sample.

[0046] Those skilled in the art will understand that the aspects can be implemented as a system, method, or apparatus program product.

[0047] Therefore, the embodiments may take the form of a completely hardware implementation or an implementation that includes software, both of which can be collectively referred to herein as a “circuit,” a “module,” or a “system.” Furthermore, the embodiments may take the form of a device program product embodied in one or more device-readable media containing device-readable program code.

[0048] 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), wherein the instructions are executed by a processor. In the context of this document, the storage device is not a signal, and "non-transient" includes all media other than signal media.

[0049] The program code used to perform the operation can be written in any combination of one or more programming languages. The program code can be executed entirely on a single device, partially on a single device, as a standalone software package, partially on a single device and partially on another device, or entirely on another device. In some cases, the device can be connected via any type of connection or network (including local area networks (LANs) or wide area networks (WANs), or via other devices (e.g., via the internet through an internet service provider), via wireless connections (e.g., near-field communication), or via hard-wired connections (e.g., via USB).

[0050] Exemplary embodiments are described herein with reference to the accompanying drawings, which illustrate exemplary methods, apparatuses, and products according to various exemplary embodiments. It is to be understood that actions and functions can be implemented at least in part by program instructions. These program instructions can be provided to the processor of a device (e.g., a handheld measuring device) or other programmable data processing device to produce a machine, such that the instructions, executed by the device's processor, perform the specified functions / actions.

[0051] It should be noted that the values ​​provided herein should be interpreted to include equivalent values ​​indicated by the term "about". Equivalent values ​​will be obvious to those skilled in the art, but at least include values ​​obtained by ordinary rounding of the last significant digits.

[0052] This disclosure has been provided for illustrative and descriptive purposes, but is not intended to be exhaustive or limiting. Many changes and variations will be apparent to those skilled in the art. Exemplary embodiments have been chosen and described to explain the principles and practical applications, and to enable others skilled in the art to understand the disclosure of multiple embodiments with various modifications suitable for the intended particular purpose.

[0053] Therefore, although exemplary embodiments have been described herein with reference to the accompanying drawings, it should be understood that this description is not restrictive, and various other changes and modifications can be made therein without departing from the scope and spirit of this disclosure.

Claims

1. A method for measuring the amount of manganese in an aqueous sample, the method comprising: The water sample was reduced using a dechlorinating agent, wherein the dechlorinating agent contained iron(II) and potassium iodide; Mn(II) in the aqueous sample was oxidized to Mn(IV) under alkaline conditions using sodium hydroxide. Then, Fe(II) and Fe(III) in the aqueous sample were chelated using hydroxyethyl phosphate (HEDP), and a certain amount of 3,3',5,5'-tetramethylbenzidine (TMB) was oxidized with Mn(IV). The amount of manganese in the aqueous sample was measured by using 3,3',5,5'-tetramethylbenzidine (TMB) as a colorimetric indicator and measuring the absorbance intensity of a certain amount of oxidized 3,3',5,5'-tetramethylbenzidine (TMB) at a certain wavelength.

2. The method according to claim 1, wherein the dechlorinating agent further comprises dilute acid.

3. The method according to claim 2, wherein the dilute acid comprises 0.85% hydrochloric acid.

4. The method according to claim 1, wherein the aqueous sample further comprises an interfering substance selected from the group consisting of free chlorine and monochloramine.

5. The method according to claim 1, wherein the absorbance intensity of the oxidized TMB is proportional to the concentration of manganese in the aqueous sample.

6. The method of claim 1, wherein the measurement includes determining the concentration of manganese based on a calibration curve.

7. The method of claim 1, wherein the measurement wavelength is 450 nanometers.

8. The method of claim 1, wherein the measurement comprises comparing the absorbance intensity of the aqueous sample at the wavelength with the absorbance intensity of a blank at a certain wavelength.

9. The method according to claim 1, wherein in the aqueous sample, Fe(II) and Fe(III) are completely chelated, and Mn(II) is completely oxidized to Mn(IV).

10. The method of claim 1, wherein the aqueous sample includes a sample for water quality testing.

11. An apparatus for measuring the amount of manganese in an aqueous sample, the apparatus comprising: Measurement room; and A memory device storing processor-executable instructions for: measuring the amount of manganese in an aqueous sample by measuring the absorbance intensity of a certain amount of oxidized 3,3',5,5'-tetramethylbenzidine (TMB) at a certain wavelength using 3,3',5,5'-tetramethylbenzidine (TMB) as a colorimetric indicator, wherein the aqueous sample is reduced using a dechlorinating agent comprising iron(II) and potassium iodide, wherein Mn(II) in the aqueous sample is oxidized to Mn(IV) under alkaline conditions using sodium hydroxide, and wherein hydroxyethyl phosphate (HEDP) chelates Fe(II) and Fe(III) in the aqueous sample.

12. The apparatus of claim 11, wherein the dechlorinating agent further comprises a dilute acid.

13. The apparatus of claim 12, wherein the dilute acid comprises 0.85% hydrochloric acid.

14. The apparatus of claim 11, wherein the aqueous sample further comprises an interfering substance selected from the group consisting of free chlorine and monochloramine.

15. The apparatus of claim 11, wherein the absorbance intensity of the oxidized TMB is proportional to the concentration of manganese in the aqueous sample.

16. The apparatus of claim 11, wherein the measurement includes determining the concentration of manganese based on a calibration curve.

17. The apparatus of claim 11, wherein the measurement wavelength is 450 nanometers.

18. The apparatus of claim 11, wherein the measurement comprises comparing the absorbance intensity of the aqueous sample at the wavelength with the absorbance intensity of a blank at a certain wavelength.

19. The apparatus according to claim 11, wherein in the aqueous sample, Fe(II) and Fe(III) are completely chelated, and Mn(II) is completely oxidized to Mn(IV).

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