Reducing agent for arsenic measurement

Abstract

One embodiment provides a method for measuring arsenic in a sample that shows a significant increase in sensitivity over previous methods, the method comprising: preparing a compound plated with zinc and zinc; introducing the compound into an acidified sample, wherein the sample contains an amount of arsenic, wherein the compound reduces the amount of arsenic to produce arsine gas; wherein sufficient hydrogen gas is produced to purge the sample solution; wherein the arsine gas is completely purged from the sample and captured on a test pad, wherein the pad comprises mercury bromide, wherein the capturing produces a color change of the pad; and measuring the amount of arsenic in the sample by measuring the color change of the pad. Other aspects are described and claimed.

Description

[0001] Cross-references to related applications

[0002] This application claims priority to U.S. Patent Application Serial No. 17 / 345,359, filed June 11, 2021, entitled “Reducing Agent for Arsenic Measurement,” the contents of which are incorporated herein by reference. Background Technology

[0003] This application generally relates to the measurement of arsenic in samples, and more specifically to the measurement of arsenic using plated zinc.

[0004] Arsenic is a naturally occurring component found in water. It can be introduced into water from rocks or sediments. Arsenic can also be introduced through human activities. Mining, pesticides, manufacturing, and other industries can introduce arsenic into groundwater. Even at low levels, arsenic can be toxic to animals. Arsenic is also a known carcinogen. Treatment facilities require careful measurement and monitoring of arsenic levels. Regulatory agencies set limits for arsenic, and detection at low concentrations ensures that treatment facilities comply with regulations.

[0005] Currently available commercially available field test kits employ the Gutzeit test, in which zinc metal is added to an acidified sample that may contain arsenic. The arsenic in the sample is reduced to arsenic gas by zinc, which must then be purged from the aqueous sample by potential hydrogen generation or mechanical agitation. Recent scientific research has demonstrated the limitations of this type of test kit (see R.R. Reddy et al., 2019, Evaluation of arsenic field testkits for drinking water: Recommendations for improvement and implications for arsenic-affected regions such as Bangladesh, Water Research 170(2020)115325). Further improvements to cost-effective field arsenic testing are needed. Summary of the Invention

[0006] In summary, one embodiment provides a method for measuring arsenic in a sample, the method comprising: providing a zinc plating and a zinc compound; introducing the compound into the sample, wherein the sample contains a certain amount of arsenic, wherein the compound reduces the certain amount of arsenic to produce arsenic gas; capturing the arsenic gas on a test pad, wherein the test pad contains mercuric bromide, wherein the capture produces a color change in the test pad; and measuring the amount of arsenic in the sample by measuring the color change in the test pad.

[0007] Another embodiment provides a method for measuring arsenic in a sample, the method comprising: preparing a zinc plating and a zinc compound, wherein the metal comprises a zero-valent metal; acidifying the sample using an acid; introducing the compound into the acidified sample, wherein the sample contains a certain amount of arsenic, wherein the compound reduces the certain amount of arsenic to produce arsenic gas and hydrogen gas; capturing the arsenic gas on a test pad, wherein the pad contains mercuric bromide, wherein the capture produces a color change in the pad; and measuring the amount of arsenic in the sample by measuring the color change of the pad.

[0008] Another embodiment provides a method for measuring arsenic in a sample, the method comprising: preparing a compound selected from the group consisting of pure metals and mixtures of pure metals and zinc, wherein the metal is in a zero valence state; acidifying the sample using an acid; introducing the compound into the acidified sample, wherein the sample contains a certain amount of arsenic, wherein the compound reduces the certain amount of arsenic to produce arsenic gas and hydrogen gas; capturing the arsenic gas on a test pad, wherein the pad contains mercuric bromide, wherein the capture produces a color change in the pad; and measuring the amount of arsenic in the sample by measuring the color change of the pad.

[0009] 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.

[0010] To better understand the embodiments and their other and additional features and advantages, reference is made to the following description in conjunction with the accompanying drawings. The scope of the invention will be defined in the appended claims. Attached Figure Description

[0011] Figure 1 A flowchart of an exemplary arsenic measurement system is shown.

[0012] Figure 2 An exemplary transition of the calibration curve of a test pad used for arsenic measurement to a darker color is shown.

[0013] Figure 3 An example of a computer circuit system is shown. Detailed Implementation

[0014] 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.

[0015] 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.

[0016] 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 specific embodiments.

[0017] Conventional methods for measuring and detecting arsenic have several drawbacks. For example, many arsenic test kits use color indicators to compare with known standard colors. At low concentrations of arsenic, these colors may be off-white or very pale yellow. Distinguishing between arsenic concentrations at these pale colors can be difficult, leading to errors in distinguishing between off-white and pale yellow at the lower end of the concentration detection plate.

[0018] One method for detecting arsenic uses the Gutzee test, which was introduced in the late 19th century. Other arsenic test kits have been introduced to the market; however, the method remains similar. The chemistry of the arsenic test remains the same. For example, the arsenic test may require the reduction of inorganic arsenic in aqueous form to arsene gas. The arsene gas must then be purged from the aqueous solution. The purged gas can then be captured on a test strip. The color of the test strip indicates the presence or concentration of arsenic in the sample.

[0019] Routine arsenic measurements may require stirring. In other words, the arsenic-containing sample used for measurement may require physical agitation or a stirring device. Stirring may be necessary to move the arsenic gas to the test strip. Conventional methods may not capture all the arsenic gas on the test strip. This inefficiency can lead to false negatives or incorrect low readings due to the presence of arsenic in the sample. What is needed is a reliable, field-usable test for arsenic that captures the arsenic gas more completely on the test strip.

[0020] Therefore, one embodiment provides a method and system for measuring arsenic using a reducing agent. In one embodiment, a dual-action method can be used to reduce arsenic to arsenic and generate an amount of hydrogen sufficient to completely purge arsenic from the sample. In one embodiment, the metal can be plated on zinc, or the metal can be in a zinc-free zero state. The metal can be nickel, copper, tin, silver, iron, etc., and can be in a pure state or a mixture of them. The metal can be in a zero valence state. Electrolytic plating of the metal on zinc can be used. The plated zinc, such as nickel-zinc plating, can be combined with zinc to form a compound. Nickel-zinc plating and / or zinc can be introduced into a sample containing a certain amount of arsenic. In one embodiment, zinc can primarily reduce arsenic to arsenic. Nickel-zinc plating can primarily generate hydrogen. Hydrogen can be generated vigorously, eliminating the need for mechanical stirring or agitation. The generated arsenic can be captured on a test pad. The test pad can contain mercuric bromide. The color change of the test pad can be correlated with the amount of arsenic in the sample. In one implementation, nickel-zinc plating can cause the standard calibration curve of the test pad to shift to a darker color. A darker color, or stronger arsenic capture, can allow for more accurate arsenic measurements at lower arsenic concentrations.

[0021] 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.

[0022] Reference Figure 1 Exemplary methods and systems for detecting arsenic in solution are shown. In one embodiment, a compound of nickel-zinc and zinc can be prepared. The compound can be introduced into a sample, wherein the sample may contain a certain amount of arsenic. Arsenic can be reduced to arsenic gas. Arsenic gas can be captured on a test pad. A color change of the test pad can measure the presence or concentration of a certain amount of arsenic in the sample.

[0023] At point 101, in one embodiment, a compound can be prepared. The compound can contain a metal, a metal plated with another metal, or a combination thereof. For example, the plating can be a metal such as cobalt, nickel, tin, iron, silver, or other metals that can be actively or passively plated onto zinc. For ease of reading, nickel can be used as an example; however, other metal platings can be used. The compound can contain nickel-zinc plating, zinc, or a combination thereof. Nickel plating of zinc can be carried out by electrolysis. In other words, an electrochemical reaction can place nickel on the surface of zinc. The plating can be complete and encapsulate zinc. Alternatively, the nickel plating can be part of the surface of zinc. In one embodiment, the nickel can be particles with a size of about 100 mesh. In one embodiment, nickel can be plated onto zinc using about 2 mg / g (2 mg nickel per 1 gram of zinc). This nickel-zinc plating is then mixed with unplated zinc at a ratio of 1 to 2 parts to 20. In one embodiment, a combination of nickel-zinc plating and zinc can be prepared. The metal and plating metal can be in the form of small pieces, granules, or fine powder. The ratio of metal to plating metal portion can be varied. The size and ratio of the metals can be adjusted to appropriately generate hydrogen. In one embodiment, another metal, such as copper, can be used for the coating. In one embodiment, the metal can be in a zero valence state. In other words, a +2 or +3 valence state where the metal is a soluble salt may not be preferred.

[0024] In one implementation, the nickel-zinc plating and zinc compound can be described as having a dual function. For example, zinc can reduce arsenic, while nickel can utilize hydrogen to purge the sample solution to remove arsenic gas. Additionally, the process of stirring the sample solution can be eliminated. In other words, the combination of nickel and zinc allows for more sensitive measurement and detection of arsenic in the sample solution without altering the stirring technique.

[0025] At point 102, in one embodiment, a compound may be introduced into a solution or sample. In one embodiment, the sample may be acidified with hydrochloric acid, sulfamic acid, or other suitable acid. The compound may comprise nickel-zinc plating. The sample solution may contain a certain amount of arsenic. The sample solution may be an aqueous sample, which may include samples from water treatment facilities, natural water bodies, industrial process facilities, storage tanks, treatment tanks, pipelines, etc. The sample solution may be in a continuously flowing state, a static volume of liquid, or any combination thereof. Nickel-zinc plating and / or zinc may have a dual function. In one embodiment, zinc may reduce arsenic to arsenic gas. In one embodiment, nickel may be used to purge the sample solution with hydrogen to remove arsenic gas. Sufficient purging of arsenic gas can lead to more accurate measurements because more arsenic gas comes into contact with or is captured by the test pad. In one embodiment, sulfamic acid may be added to the reaction. Sulfamic acid may be in liquid, powder, or powder pillow form. If the sample volume is large, for example when increasing the volume from 50 ml to 75 ml, aminosulfonic acid can be used to maintain acidic conditions.

[0026] In one embodiment, a sample solution may be placed in a reaction vessel for arsenic testing. In another embodiment, the sample solution may be introduced into a compound (e.g., the test chamber of a measuring device). In one embodiment, the measuring device may be a handheld device. Alternatively, the measuring device may be a larger benchtop device. Testing for arsenic can be performed on-site using test kits, portable devices, etc. Introducing the sample solution into the measuring device may include manually or mechanically placing or introducing the solution into the test chamber by a user (e.g., gravity flow, pump, pressurized fluid flow, etc.). For example, a pump may be used to introduce an aqueous sample for arsenic testing into the measuring chamber or test chamber. In one embodiment, valves, etc., may control the inflow and outflow of the solution into or from one or more chambers (if present). Alternatively, the measuring device may be directly connected to a processing or characterization measurement system.

[0027] Alternatively or concurrently, the measuring device may be present in or introduced into a volume of solution. The measuring device is then exposed to that volume of solution, where it can perform measurements. The system may be a flow system in which solutions 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 arsenic 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.

[0028] At point 103, in one embodiment, the method and system can utilize a color change in a test pad to measure the amount of arsenic in a sample solution. In one embodiment, a certain amount of arsenic can be reduced to arsenic gas by zinc. In one embodiment, nickel or a nickel plating can properly purge the arsenic gas so that it can contact the test pad. The test pad may contain mercuric bromide. The reaction of arsenic gas with the mercuric bromide pad causes a color change in the test pad. For example, a low amount of arsenic in the sample solution can produce a grayish-white or light yellow or yellow color. As another example, a higher amount of arsenic in the sample solution can produce a light brown, brown, or dark brown color. A moderate amount of arsenic produces a hue between yellow and brown.

[0029] Reference Figure 2 Conventional arsenic detection methods may struggle to visually determine hues ranging from grayish-white to pale yellow, making it difficult to detect even low levels of arsenic in sample solutions using the human eye or even color-sensitive equipment. For example, in Figure 2 The image shows a series of standard arsenic detection kit test pads (large squares) and, as an insert, test pads using nickel-zinc plating (small squares). Standard methods show a range of arsenic detection levels from 0 ppb (parts per billion) white, to 50 ppb light yellow, to 200 ppb yellow, and 500 ppb reddish-brown. Note that the 50 ppb nickel-zinc plating results in a color change similar to that observed in standard tests at 300-400 ppb. In one embodiment, the use of dual-action nickel-zinc plating produces a test pad signal that is 2-6 times stronger than the signal obtained using currently commercially available methods at an arsenic concentration of 50 ppb. Nickel, or a nickel plating, enables the generation of hydrogen gas. Nickel does not interfere with the reduction of arsenic to arsenic. The generation of hydrogen allows for better transfer of arsenic to the test pad. In one embodiment, nickel can be plated onto zinc at approximately 2 mg / g (2 mg nickel per 1 gram of zinc). The nickel-zinc plating is then mixed with unplated zinc at a ratio of 1 to 20 parts per 1 part ...

[0030] At point 104, in one embodiment, the system and method can determine whether the amount of arsenic in the solution can be measured. In one embodiment, the presence of arsenic in the aqueous solution can result in a deeper color being observed on the test pad. Therefore, the observed color of the test pad for testing a solution containing a certain amount of arsenic can be correlated with the color of the test pad at a known concentration of arsenic in the aqueous solution or sample solution. In other words, the determination of the amount of arsenic can be performed by human observation or automated using an instrument capable of determining the color of the test pad.

[0031] Alternatively or additionally, the amount or concentration of arsenic can be measured at user-defined periodic intervals or at pre-programmed frequencies within the device. Device-based arsenic measurement allows for real-time data acquisition with minimal human intervention during the measurement process. Cleaning of the measurement chamber or reaction chamber may be required at unspecified intervals. Programmed calibration curves can be input into the device.

[0032] Chambers, containers, units, etc., can hold aqueous samples, zinc, zinc plating, and related reagents such as buffers and / or additives. The apparatus may include bottles / containers containing one or more reagents and / or metals. The reagents contained in one or more bottles or containers can be pumped or gravity-fed. The flow of reagents can be metered to ensure appropriate volume delivery to the measuring unit. Aqueous samples can be fed via 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, metals, and related reagents.

[0033] The measurement results of arsenic can be output in the form of display, printing, storage, audio, haptic feedback, etc. on the device. Alternatively or additionally, the output results can be transmitted via wired, wireless, fiber optic, etc. Near-field communication, etc., is transmitted to another device. One implementation may use an alarm to warn of measurements or concentrations outside acceptable levels. Another implementation may use the system to shut off water output or divert water from sources with unacceptable levels. For example, the analyte measuring device may use a relay connected to an electric valve, etc.

[0034] At point 106, in one implementation, if the amount of arsenic cannot be determined, the system can continue to measure the amount of arsenic with samples of the same or different volumes. In one implementation, new test pads and associated reagents (such as nickel-zinc and zinc plating) can be used. Alternatively or additionally, the system can output alarms, log events, etc.

[0035] At point 105, if the amount of arsenic can be determined, the system can provide a measurement result of the amount of arsenic in the solution. In one embodiment, the color of the test pad can be associated with a known test pad concentration and the recorded and measured results. 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 an arsenic measurement result has been determined. The alarm can be in the form of sound, visual, data, data storage in a memory device, sending output results through a connected system or wireless system, printing output results, 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 or concentration of arsenic reaches a threshold. Alarms or logs can be analyzed in real time, stored for later use, or any combination thereof.

[0036] Therefore, the embodiments described herein represent technical improvements to conventional arsenic measurement techniques. Using the techniques described herein, one embodiment can use a reducing agent (such as nickel-zinc plating) to measure the amount of arsenic in a solution. The methods and systems described herein provide a more accurate and sensitive method for measuring arsenic in aqueous or liquid solutions.

[0037] Although various other circuits, circuit systems, or components may be used in information processing devices, regarding the instrument for arsenic measurement according to any of the embodiments described herein, Figure 3 An example is shown. Device circuitry 10' may include a measurement system based on an established chip design, such as a specific computing platform (e.g., mobile computing, desktop computing, etc.). Software and one or more processors are integrated into a single chip 11'. As is well known in the art, a processor includes internal arithmetic units, registers, cache memory, buses, I / O ports, etc. Internal buses, etc., vary depending on the vendor, but essentially all peripherals (12') can be connected to a single chip 11'. Circuitry 10' integrates the processor, memory controller, and I / O controller hub into a single chip 11'. Furthermore, this type of system 10' generally does not use SATA, PCI, or LPC. For example, common interfaces include SDIO and I2C.

[0038] 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, a single chip, such as 11', provides BIOS-like functionality and DRAM memory.

[0039] 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 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 and located away from the single-beam system setup). System 10' typically also includes various memory devices, such as flash memory 18' and SDRAM 19'.

[0040] 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, and 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 arsenic in an aqueous sample.

[0041] Those skilled in the art will understand that each aspect can be embodied as a system, method, or device program product. Therefore, each aspect can take the form of a completely hardware implementation or an implementation including software, which herein can be collectively referred to as a “circuit,” “module,” or “system.” Furthermore, each aspect can take the form of a device program product, which is embodied as one or more device-readable media containing device-readable program code.

[0042] 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.

[0043] 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).

[0044] 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 processor of the device, perform the specified functions / actions.

[0045] 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.

[0046] 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 those skilled in the art to understand the disclosure of multiple embodiments with various modifications suitable for the intended particular purpose.

[0047] 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 arsenic in a sample, the method comprising: Provided a mixture of plating zinc and zinc, wherein the mass ratio of plating zinc to zinc is between 1 and 2 parts per 20, wherein the metal is selected from nickel, copper, tin, silver and iron, and is in pure form or a mixture of them; The zinc plating and zinc mixture is introduced into the acidified sample, wherein the sample contains a certain amount of arsenic, and wherein the zinc plating and zinc mixture reduces the certain amount of arsenic to produce arsenic gas. The arsenic gas is captured on a test pad containing mercuric bromide, and the capture produces a color change in the pad. as well as The amount of arsenic in the sample is measured by measuring the color change of the pad.

2. The method of claim 1, wherein the preparation of the zinc plating comprises electrolysis to plate the metal onto the zinc.

3. The method according to claim 1, wherein the zinc plating is prepared by using 2 milligrams of metal to 1 gram of zinc.

4. The method of claim 1, wherein the metal is in a zero valence state.

5. The method of claim 1, wherein the metal coating generates hydrogen gas sufficient to purge arsenic from the sample, but does not negatively affect the reduction of arsenic to arsenic.

6. The method according to claim 1, further comprising adding aminosulfonic acid to reduce the amount of arsenic.

7. The method of claim 1, wherein the zinc plating causes the calibration curve of the test pad according to the color change to produce a deeper color.

8. The method of claim 1, wherein the color change of the test pad is related to the amount of arsenic in the sample.

9. The method of claim 1, wherein physical stirring of the sample is not required during the reduction.

10. The method of claim 1, wherein the sample comprises a water sample.

11. A method for measuring arsenic in a sample, the method comprising: Prepare a mixture of metallized zinc and zinc, wherein the mass ratio of the metallized zinc to the zinc is between 1 and 2 parts by mass (20 parts by mass), wherein the metal includes zero-valent metals, and wherein the metal is selected from nickel, copper, tin, silver and iron, and is in pure state or a mixture of them; The sample was acidified using an acid; The mixture is introduced into an acidified sample containing a certain amount of arsenic, wherein the mixture reduces the certain amount of arsenic to produce arsenic gas and hydrogen gas; The arsenic gas is captured on a test pad containing mercuric bromide, and the capture produces a color change in the pad. as well as The amount of arsenic in the sample is measured by measuring the color change of the pad.

12. The method of claim 11, wherein the preparation comprises electrolysis to plate the metal onto the zinc.

13. The method of claim 11, wherein the zinc plating is prepared by using 2 milligrams of metal to 1 gram of zinc.

14. The method of claim 11, wherein the metal is in a zero valence state.

15. The method of claim 11, wherein the metal coating generates hydrogen gas sufficient to purge arsenic from the sample, but does not negatively affect the reduction of arsenic to arsenic.

16. The method of claim 11, further comprising adding aminosulfonic acid to reduce the amount of arsenic.

17. The method of claim 11, wherein the zinc plating causes the calibration curve of the test pad according to the color change to produce a deeper color.

18. The method of claim 11, wherein the color change of the test pad is related to the amount of arsenic in the sample.

19. The method of claim 11, wherein physical stirring of the sample is not required during the reduction.

20. A method for measuring arsenic in a sample, the method comprising: Prepare a compound, wherein the compound is selected from the group consisting of: pure metals, and mixtures of pure metals and zinc, wherein the zinc is plated with the pure metal, wherein the pure metal is in a zero valence state, and wherein the pure metal is selected from nickel, copper, tin, silver and iron; The sample was acidified using an acid; The compound is introduced into an acidified sample containing a certain amount of arsenic, wherein the compound reduces the certain amount of arsenic to produce arsenic gas and hydrogen gas. The arsenic gas is captured on a test pad containing mercuric bromide, and the capture produces a color change in the pad. as well as The amount of arsenic in the sample is measured by measuring the color change of the pad.

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