WO2024005719A1

WO2024005719A1 - Analyser and computer-implemented method for pollutant detection

Info

Publication number: WO2024005719A1
Application number: PCT/SG2023/050465
Authority: WO
Inventors: Ten It Wong; Xiao Dong Zhou; Ke Zhao; Liya GE; Grzegorz LISAK
Original assignee: Agency For Science, Technology And Research; Nanyang Technological University
Priority date: 2022-06-30
Filing date: 2023-06-30
Publication date: 2024-01-04

Abstract

An analyser (10, 100) for pollutant detection and a computer-implemented method (200) for pollutant detection are provided. The analyser (10, 100) includes one 5 or more electrochemical detection units (12, 102), one or more processors (14), a non-transitory computer-readable memory (16) and a display (18). Each of the one or more electrochemical detection units (12, 102) is configured to receive a control voltage signal according to a pollutant-specific detection protocol and output a measured current signal based on a measured electrical current from an electrode chip (20). The non-transitory 0 computer-readable memory (16) stores a detection protocol for each of a plurality of pollutants, a characterisation curve for each of the pollutants and computer program instructions executable by the one or more processors (14) to perform operations for pollutant detection, the operations comprising: identifying a current peak in the measured current signal; determining a peak intensity corresponding to the identified current peak; 5 and determining a concentration of a selected pollutant from the characterisation curve of the selected pollutant based on the determined peak intensity. The display (18) is configured to display the concentration of the selected pollutant.

Description

ANALYSER AND COMPUTER-IMPLEMENTED METHOD FOR POLLUTANT DETECTION

Field of the Invention

The present invention relates in general to detection of pollutants and more particularly to an analyser for pollutant detection and a computer-implemented method for pollutant detection.

Background of the Invention

Heavy metal ions are highly toxic to humans, animals and the environment, causing chronic or even fatal damage with trace amounts at parts per million (ppm) concentrations. Consequently, rapid on-site detection of heavy metal ions is of great importance for solid waste disposal, wastewater discharge and hazard identification to prevent the spread of pollutants.

For concentration measurement of heavy metal ions, laboratory characterization using bulky and expensive equipment such as atomic absorption spectrophotometer (AAS), inductively coupled plasma-mass spectrometer (ICP-MS) or inductively coupled plasma-optical emission spectrometer (ICP-OES) usually takes several days from sample collection to test completion. This also imposes potential risks on sample conditions, which may undergo changes in heavy metal status whilst being transported from a site to a laboratory. Laboratory characterizations also require customers to wait for concentration measurement results before making decisions on waste disposal.

In addition to heavy metals, some other pollutants, such as phenolic compounds and iodide, are also environmental pollutants of great concern. Phenolic compounds are common contaminants in industrial wastewater, especially in sectors associated with oil refineries, metallurgies, petrochemicals, steelworks, dyes, ceramic plants, pesticides, and phenolic resin manufacturing, and are harmful to organisms even at low concentrations. Phenolic compound and iodide concentrations are usually determined by ultraviolet-visible (UV-Vis) spectrophotometer, but a significant flaw of this method is that it could be interfered with by particles and coloured substances in the sample, which are very common in environmental samples. Several types of portable heavy metal ion sensors have been reported. Amongst these, electrochemical (EC) detection is a reliable method for on-site heavy metal ion detection without much interference from other ion types. This method identifies each species of heavy metal ion in a solution specifically based on current change caused by redox reaction on a surface or modified surface of EC electrodes. Two types of heavy metal ion detectors based on EC detection are currently available: on-site portable or online devices for heavy metal ion detection. Drawbacks of these devices include a requirement for external computer and software to analyse data manually as the data cannot be automatically analysed and thus these devices are not standalone. Another drawback is that these devices reuse large electrodes, requiring users to clean the electrodes after each use. Failure to thoroughly clean the electrodes could cause crosscontamination from sample to sample, compromise reliability and/or introduce inconsistency of results. A further drawback is that each device has only one-channel of EC detector. Therefore, the detector only detects one species of heavy metal ions for each measurement and each measurement takes several minutes to tens of minutes.

Commercially available portable analysers for iodide are based on an ion- selective electrode (ISE) and an electrical conductivity reader measuring current from an iodide ISE. Such devices may take about 10 minutes (min) for on-site manual detection of iodide. The ISE is disposed after a number of uses and cannot measure iodide reliably in the presence of Ag⁺, S^2-, Hg²⁺, or CN^_ due to interferences by such ions. No portable analyser or detector is currently commercially available for total phenolic compounds.

Summary of the Invention

In a first aspect, the present invention provides an analyser for pollutant detection. The analyser includes one or more electrochemical detection units, one or more processors, a non-transitory computer-readable memory and a display. Each of the one or more electrochemical detection units is configured to receive a control voltage signal according to a pollutant-specific detection protocol and output a measured current signal based on a measured electrical current from an electrode chip. The non-transitory computer-readable memory stores a detection protocol for each of a plurality of pollutants, a characterisation curve for each of the pollutants and computer program instructions executable by the one or more processors to perform operations for pollutant detection, the operations comprising: identifying a current peak in the measured current signal; determining a peak intensity corresponding to the identified current peak; and determining a concentration of a selected pollutant from the characterisation curve of the selected pollutant based on the determined peak intensity. The display is configured to display the concentration of the selected pollutant.

In a second aspect, the present invention provides a computer-implemented method for pollutant detection. The method includes comprising executing via one or more processors the steps of: receiving a measured current signal based on a measured electrical current from each of one or more electrode chips; identifying a current peak in the measured current signal; determining a peak intensity corresponding to the identified current peak; and determining a concentration of a selected pollutant from a characterisation curve of the selected pollutant based on the determined peak intensity.

Other aspects and advantages of the invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.

Brief Description of the Drawings

Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

FIG. 1A is a schematic block diagram illustrating an analyser for pollutant detection in accordance with an embodiment of the present invention;

FIG. 1 B is a photograph of the analyser for pollutant detection of FIG. 1A;

FIGS. 1C through 1 F are characterization curves embedded in the analyser of FIG. 1A;

FIG. 1G is a schematic diagram illustrating a user interface of the analyser of FIG. 1A;

FIG. 1 H is a schematic flow diagram illustrating an operational flow of the analyser of FIG. 1A; FIG. 2A is a schematic block diagram illustrating an analyser for pollutant detection in accordance with another embodiment of the present invention;

FIG. 2B is a photograph of the analyser for pollutant detection of FIG. 2A;

FIG. 2C is a photograph of accessories for the analyser of FIG. 2A;

FIG. 2D is a photograph of a sample loading setup for the analyser of FIG. 2A;

FIG. 2E is a schematic flow diagram illustrating an operational flow of the analyser of FIG. 2A;

FIG. 2F is a schematic diagram illustrating a user interface of the analyser of FIG. 2A;

FIG. 2G is a schematic flowchart illustrating a workflow when using the analyser of FIG. 2A;

FIGS. 2H through 2M illustrate user interface changes over the workflow of the analyser according to FIG. 2G;

FIG. 3 is a schematic flow diagram illustrating a computer-implemented method for pollutant detection in accordance with an embodiment of the present invention;

FIG. 4A is a photograph of an on-site test using a portable multi-channel analyser in accordance with an embodiment of the present invention for solid waste leachate; and

FIG. 4B is a schematic diagram illustrating a user interface of the portable multichannel analyser of FIG. 4A; and

FIG. 4C is a schematic diagram illustrating an automatically generated report for heavy metal ion, iodide and total phenolic compound detections by the multi-channel analyser of FIG. 4A.

Detailed Description of Exemplary Embodiments

The detailed description set forth below in connection with the appended drawings is intended as a description of presently preferred embodiments of the invention, and is not intended to represent the only forms in which the present invention may be practiced. It is to be understood that the same or equivalent functions may be accomplished by different embodiments that are intended to be encompassed within the scope of the invention. In the accompanying figures, like references indicate similar elements.

Referring now to FIGS. 1A and 1 B, an analyser 10 for pollutant detection is shown. The analyser 10 includes an electrochemical detection unit 12, one or more processors 14, a non-transitory computer-readable memory 16 and a display 18.

The analyser 10 of the present embodiment is an electrochemical (EC) based handheld one-channel analyser for on-site detection of heavy metal ions and other pollutants and includes hardware, software and electrochemical detection recipes. The analyser 10 may be viewed as three (3) parts: an electrochemical (EC) detector unit, a single-board computer (SBC) including software, and a power supply and a touch screen. Advantageously, the single-board computer (SBC) may be programmed and integrated inside the stand-alone portable analyser 10; no external computer is required.

The electrochemical detection unit 12 is configured to receive a control voltage signal according to a pollutant-specific detection protocol and output a measured current signal based on a measured electrical current from an electrode chip 20.

The electrode chip 20 may include a counter electrode (CE), a reference electrode (RE) and a working electrode (WE). The counter electrode (CE), the reference electrode (RE) and the working electrode (WE) may be screen-printed onto a chip body. A sample under test experiences a redox reaction leading to a measurable electrical current passed between the counter electrode (CE) and the working electrode (WE).

Heavy metal ions may be detected by voltammetry, whose signal is analysed by a current-potential curve. Voltammetry may have different modes for heavy metal and other pollutant detection, for example, cyclic voltammetry (CV), square wave voltammetry (SWV), linear sweep voltammetry (LSV) and differential pulse voltammetry (DPV) and involves preconcentration and detection processes. During the preconcentration stage, heavy metal ions are reduced and concentrated at the working electrode (WE) by a voltage opposite to the ion charge (i.e., negative voltage for cations, and positive voltage for oxyanions). For the detection process, a reverse electrode potential is applied to strip heavy metal from the working electrode (WE). A current peak between the working electrode (WE) and the counter electrode (CE) is recorded during heavy metal dissolution, and corresponding peak intensity is used to quantify heavy metal concentration.

The electrochemical detection unit 12 may include a digital-to-analogue converter 24 configured to convert a plurality of control voltages in the control voltage signal into a control voltage waveform for pollutant detection. As the control voltages received by the electrochemical detection unit 12 may be in digital form, the control voltages may be turned into an analogue voltage supply by the digital-to-analogue converter 24 to impose various voltage conditions onto the electrode chip 20.

The electrochemical detection unit 12 may include a current-to-voltage converter 26 configured to convert the measured electrical current received from the electrode chip 20 into a measured voltage waveform. Current intensity (proportional to analyte concentration) may first be turned into an analogue voltage by the current-to-voltage convertor 26.

The electrochemical detection unit 12 may further include an analogue-to-digital converter 28 configured to convert the measured voltage waveform into a digital voltage signal. The analogue voltage from the current-to-voltage convertor 26 may then be converted into a digital signal by the analogue-to-digital convertor 28.

The electrochemical detection unit 12 may further include a microcontroller 30 configured to convert the digital voltage signal into the measured current signal. More particularly, the microcontroller 30 turns the digital voltage signal from the analogue-to- digital convertor 28 into a current signal and sends the current signal to the single-board computer (SBC) for further data processing. The microcontroller 30 may also send different voltage waveforms to the screen-printed electrode chip (SPEC) 20 based on control voltages sent from the single-board computer (SBC).

The one or more processors 14 (which may be referred to as a central processor unit or CPU) may be implemented as one or more CPU chips. Three (3) major software modules may be installed in the single-board computer (SBC), namely (a) a library of detection protocols I recipes for different heavy metal ions and other pollutants, (b) an electrochemical (EC) data process and heavy metal ion concentration analysis module, and (c) a user interface for users to select recipes and run the analyser 10 through the touch screen 18.

The non-transitory computer-readable memory 16 stores a detection protocol for each of a plurality of pollutants, a characterisation curve for each of the pollutants and computer program instructions executable by the one or more processors 14 to perform operations for pollutant detection.

Electrochemical (EC) recipe development for each species of heavy metal ions and other pollutants includes selection of a most suitable SPEC, a detection buffer, a dilution ratio of the buffer and sample, a voltammetry mode specification and parameter settings for a selected voltammetry mode. Adjustment of these conditions affects effective measurement, detection sensitivity and detection range of a pollutant. Accordingly, the detection protocol for each of the pollutants may include a screen- printed electrode chip (SPEC) specification, a detection buffer, a dilution factor, a voltammetry mode specification and parameter settings for a selected voltammetry mode.

As an example, electrochemical (EC) recipes developed for fourteen (14) species of heavy metal ions including Ag(l), As(lll), Cd(ll), Cr(VI), Cu(ll), Fe(l l+ 111), Mn(ll), Mo(VI), Ni(ll), Pb(ll), Sb(lll), V(V), Zn (II), Hg(ll)), iodide and total phenolic compounds that may be incorporated into the analyser 10 are summarized in Table 1 below.

Table 1 . Voltammetry modes and SPECs for detection of various heavy metal ions (Ag(l), As(lll), Cd(ll), Cr(VI), Cu(ll), Fe(ll+lll), Mn(ll), Mo(VI), Ni(ll), Pb(ll), Sb(lll), V(V), Zn (II), Hg(ll)), iodide and total phenolic compounds

Detection methods for sixteen (16) analytes shown in Table 1 above may be preloaded in the recipe library inside the analyser 10 so users do not need to manually set test conditions for the analyser 10 to go through tedious protocol optimization processes, but are able to detect the analytes by just loading samples and selecting recipes for auto-detection.

After detection, a raw electrochemical (EC) detection curve is obtained with x- axis representing voltage supplied to the SPEC and y-axis representing a detected current signal. The operations for pollutant detection include: identifying a current peak in the measured current signal; determining a peak intensity corresponding to the identified current peak; and determining a concentration of a selected pollutant from the characterisation curve of the selected pollutant based on the determined peak intensity. For different concentrations of heavy metal ions, the corresponding peak of current might shift at certain ranges of voltages supplied, as shown in Table 1 above.

Referring now to FIGS. 1C through 1 F, characterization curves embedded in the analyser of FIG. 1A are shown. As peak intensity is proportional to analyte concentration, peak intensity is used to compare with the characterization curves saved in the SBC to find the concentration.

Referring again to FIGS. 1A and 1 B, the operations for pollutant detection may further include: identifying background current in the measured current signal; and deducting the background current from the measured current signal before identifying the current peak in the measured current signal. As other electrolytes inside a test solution may cause responses showing as current background at different voltages, raw EC data may first have a baseline recognition and deduction to remove background current to analyse exact concentration of targeted heavy metal ion or other pollutant after each test and then the maximum peak may be found in a targeted voltage region guided by Table 1 above.

The current signal curve from the electrochemical detection unit 12 may thus be sent to the single-board computer to (1) deduct the baseline of the current curve, (2) find the current peak based on the baseline deducted current curve, and (3) calculate pollutant concentration based on the characterization curve stored in the single-board computer.

It is understood that by programming and/or loading executable instructions onto the analyser 10, at least one of the CPU 14 and the non-transitory computer-readable memory 16 are changed, transforming the analyser 10 in part into a particular machine or apparatus having the novel functionality taught by the present disclosure. It is fundamental to the electrical engineering and software engineering arts that functionality that can be implemented by loading executable software into a computer can be converted to a hardware implementation by well-known design rules. Decisions between implementing a concept in software versus hardware typically hinge on considerations of stability of the design and numbers of units to be produced rather than any issues involved in translating from the software domain to the hardware domain. Generally, a design that is still subject to frequent change may be preferred to be implemented in software because re-spinning a hardware implementation is more expensive than respinning a software design. Generally, a stable design that will be produced in large volume may be preferred to be implemented in hardware, for example in an application specific integrated circuit (ASIC), because for large production runs the hardware implementation may be less expensive than the software implementation. Often a design may be developed and tested in a software form and later transformed, by well-known design rules, to an equivalent hardware implementation in an application specific integrated circuit that hardwires the instructions of the software. In the same manner as a machine controlled by a new ASIC is a particular machine or apparatus, likewise an analyser that has been programmed and/or loaded with executable instructions may be viewed as a particular machine or apparatus.

Additionally, after the analyser 10 is turned on or booted, the CPU 14 may execute a computer program or application. For example, the CPU 14 may execute software or firmware stored in the non-transitory computer-readable memory 16.

The display 18 is configured to display the concentration of the selected pollutant.

As can be seen from FIGS. 1A and 1 B, the analyser 10 is a standalone device including a battery 32, a battery charger 34, a touch screen or display 18, a power indicator 36 on the screen 18 and a switch 38. One or more USB connections may be provided in the analyser 10 for software updating and data transferring from the analyser 10 to computers or portable storage devices. Alternatively, data inside the analyser 10 may be sent to cloud storage or a computer by wireless connections such as, for example, Wi-Fi or Bluetooth.

The analyser 10 may last between 2 to 3 hours for on-site detection without requiring charging of the battery 32. In one embodiment, the analyser 10 may have dimensions of 146 millimetres (mm) (length) by 78 mm (width) by 60 mm (height) and a weight of about 430 grams (g).

The analyser 10 may detect heavy metal ions and other pollutants by either dripping a drop of sample onto a screen-printed electrode chip (SPEC) surface or dipping the SPEC into a sample in a cuvette.

Referring now to FIG. 1G, a user interface of the handheld one-channel analyser 10 is shown. As can be seen from the user interface of the analyser 10 depicted in FIG. 1G, a user only needs to input a desired filename, select a recipe for a heavy metal ion or other pollutant and press “RUN” to perform a measurement. A calculated concentration of the targeted heavy metal ion or other pollutant is shown on the touch screen 18 at the end of the electrochemical (EC) detection process. The user interface may indicate whether a tested sample is at a safe or dangerous level based on threshold requirements set by a regulatory authority or a limit set by the user.

Referring again to FIG. 1 B, an electrochemical (EC) detection graph after current background reduction may be presented on the user interface as shown. Failure to show the EC detection graph on the user interface may indicate a functional abnormality of the analyser 10 or improper loading of the sample.

Referring now to FIG. 1 H, operation of the handheld one-channel analyser 10 will now be described. After the analyser 10 is turned on, the user may insert a disposable screen-printed electrode chip (SPEC) into the analyser 10 and deposit a test solution on the SPEC or dip the SPEC into a cuvette with a sample for testing. The user may key in a filename, select an ion species via the touch screen 18 and activate a “RUN” button to start measurement. An EC detection recipe for a targeted heavy metal ion or other pollutant is then uploaded into the microcontroller 30 of the electrochemical detection unit 12 and the electrochemical detection unit 12 then conducts detection and sends test results to the single-board computer (SBC). Data may be processed by proper baseline subtraction to offset floating trend of background current, followed by extrema searching among processed data points. Captured value of extrema is used in a reversed calculation, which is based on a saved characterization curve for the targeted heavy metal ion or other pollutant, to obtain a concentration value that is displayed on the screen 18 and saved in the single-board computer (SBC).

If a batch of heavy metal ions and/or other pollutants are required to conduct the test, the user may input a new filename and select a new test recipe for detection.

When the last test is completed, all obtained results may be copied to a Universal Serial Bus (USB) thumb drive or the analyser 10 may simply be shut down since data are already saved inside the single-board computer (SBC).

Referring now to FIGS. 2A and 2B, an analyser 100 for pollutant detection in accordance with another embodiment of the invention is shown. The analyser 100 differs from the earlier embodiment in that the analyser 100 is a multi-channel analyser having a plurality of electrochemical detection units 102, each of the electrochemical detection units 102 being configured to receive a control voltage signal according to a pollutantspecific detection protocol and output a measured current signal based on a measured electrical current from an electrode chip. The digital voltage signal may be further processed by the microcontroller (not shown) in each of the electrochemical detection units 102 to convert the digital voltage signal into a current signal.

The analyser 100 of the present embodiment is a portable sixteen (16) channel analyser for on-site detection and includes hardware, software and electrochemical detection recipes. The primary hardware part of the portable 16-channel analyser 100 may include a single-board computer (SBC) and sixteen (16) electrochemical (EC) boards to conduct sixteen (16) channels of electrochemical (EC) detection.

To perform multiple channel analysis, a sample loader 104 interfacing the electrochemical detection units 102 may be provided. The sample loader 104 may include a cuvette holder 106 and a screen-printed electrode chip (SPEC) holder 108 in a stacked arrangement. A vibration motor 110 may be attached to the cuvette holder 106.

A power management system including a battery 32, a battery charger 34, a power switch 38 and a battery volume indicator 112 may be provided with the analyser 100. The portable 16-channel analyser 100 may be operable on-site for 2 to 3 hours without requiring charging of the battery 32. When the power switch 38 is turned on, a power supply for a cooling fan 114, the single-board computer (SBC), the electrochemical detection units 102 and the mixer vibrator 110 is switched on. The analyser 100 may have a size of 22 cm (length) by 16.5 cm (width) by 28.5 cm (height) and a mass of 4.33 kg, including all accessories.

The analyser 100 may include a 7 inch (in) touch screen 18 for a user to communicate with the analyser 100 through a user interface. When the user has input a sample filename, selected sample type I nature and a folder for measurement data to be saved, the single-board computer (SBC) loads detection recipes of the electrochemical detection units 102 to conduct electrochemical (EC) concentration measurement of heavy metal ions, iodide, and phenolic compounds. The software works together with the hardware to execute functions of the software for the portable 16-channel analyser 100. The non-transitory computer- readable memory 16 may further be configured to store computer program instructions executable by the one or more processors 14 to perform the operations for pollutant detection in respect of each of a plurality of selected pollutants simultaneously. The software part of the analyser 100 may include (a) a measurement recipe library for different analyte detections, and (b) algorithms that synchronize simultaneous detection of the 16-channels concurrently and report concentrations after completion of measurement processes.

Referring now to FIG. 2C, accessories for the portable 16-channel analyser 100 are shown. The accessories include a cuvette holder 106 for sixteen (16) cuvettes and a battery charger 34.

Referring now to FIG. 2D, a sample loading setup is shown. The sample loading setup includes (a) a screen-printed electrode chip (SPEC) holder 108, (b) a cuvette holder 106, (c) a screen-printed electrode chip (SPEC), and (d) a cuvette. A vibration motor (not shown) may be embedded inside the cuvette holder 106 underneath the cuvettes. Screen-printed electrode chips (SPECs) may be inserted into the 16-channel SPEC holder 108 kept inside a main body of 16-channel analyser 100 and the SPEC holder 108 may be stacked on top of the 16-channel cuvette holder 106 to dip the SPECs into the cuvettes for analyte detections. The vibration motor may be installed at the bottom of the 16-cuvette holder 106. When vibration is required to quickly mix a sample with a test buffer, the vibration motor may be turned on to accelerate the mixing of samples in the cuvette holder.

Referring now to FIG. 2E, operation of the portable 16-channel analyser 100 will now be described. After sample preparation and loading, a selection of sample nature may be provided via the user interface. On selection, measurements of heavy metal ions, iodide, or phenolic compounds in the 16 channels are concurrently performed. Next, measured data may be collected and processed in the SBC by deducting a background current of each channel and comparing a detected current with corresponding characterization curves saved in the SBC. A conclusion may be provided if concentration of each species exceeds a detection limit based on safety criteria. Concentration and comparison results may be displayed on the screen 18. A report based on measurements of the 16 channels may be generated.

A “PASS” result is generated if concentrations of heavy metal ion, iodide or phenolic compounds are too low to be detected or the concentrations are below regulatory limits. If a signal of an analyte (heavy metal ion, iodide, or phenolic compounds) falls out of a detection range or is within the detection range, but is higher than a regulatory limit, the concentration for that analyte is marked as “FAIL”.

Referring now to FIG. 2F, a user interface of the portable 16-channel analyser 100 is shown. As can be seen from the user interface of the analyser 100 shown in FIG. 2F, users may input file name, select sample types (i.e., raw sample or laboratory sample; this means different characterization curves are used for concentration calculation), dilution factor for a sample, and run or abort the 16-channel detection process at any time. The interface may also include a logging window for EC process progress checking.

When a sample is diluted with a buffer, a dilution factor is introduced to adjust concentration readings of heavy metal ion, iodide, or total phenolic compounds after measurement and data analysis. The dilution factor is applied to dilute a raw sample with a detection buffer. The detection buffer activates detection of a pollutant. However, a high dilution ratio dilutes a pollutant concentration in a raw sample and thus requires higher sensitivity of a sensor. A suitable dilution buffer may allow sensitive detection of a pollutant in a raw sample without affecting a satisfactory limit of detection of a protocol. The dilution factor may be identified using Equation (1) below:

Dilution Factor = (Volume of sample + Volume of buffer) I Volume of sample (1)

For example, when a sample to buffer volume ratio is 9:1 , the dilution factor is (9+1)79=1.11. The dilution factor may be determined at sample preparation and may be an input of a detection condition. When the detection is completed, the pollutant concentration may be calculated by considering the dilution ratio.

After measurement and data analysis, buttons for the heavy metal ion, iodide, or total phenolic compounds become green if the sample passes regulation criterion. Otherwise, the buttons become red, indicating a failure for a particular standard. In regard to EC detection recipe development, the portable 16-channel analyser 100 may be set to detect silver (Ag), arsenic (As), cadmium (Cd), chromium (Cr), copper (Cu), iron (Fe), manganese (Mn), molybdenum (Mo), nickel (Ni), lead (Pb), antimony (Sb), vanadium (V), zinc (Zn), mercury (Hg), iodine (I) and total phenolic compounds in 16 channels, with SPEC, EC detection method and peak position for each analyte listed in Table 1 and the characterization curves for all analytes shown in FIGS. 1C through 1 F.

Referring now to FIGS. 2G through 2M, a workflow when using the portable 16- channel analyser 100 will now be described. After switching on the portable 16-channel analyser 100, a user is required to prepare and dispense samples into the 16 cuvettes, insert SPECs into the 16-channel SPEC holder 108, and then stack the SPEC holder 108 on top of the cuvette holder 106 for auto-detection of heavy metal ions, iodide, and total phenolic compounds.

The analyser 100 is operable via the user interface on the touch screen 18. The user interface of the portable 16-channel analyser 100 allows selection of sample type and a folder to save data after tests. After completion of measurements, the user interface shows concentrations of each heavy metal ion, iodide, or total phenolic compounds on the screen 18, indicating if the sample has any analytes exceeding safety levels and a report may be generated via the 16-channel analyser 100. The user may shut down the SBC and turn off the power supply if no further measurement is required.

Having described the analysers 10 and 100 for pollutant detection, a computer- implemented method for pollutant detection will now be described below with reference to FIG. 3.

Referring now to FIG. 3, a computer-implemented method 200 for pollutant detection is shown. The method 200 for pollutant detection may be executed via the one or more processors 14 of the analyser 10 or 100.

The pollutant detection method 200 begins at step 202 by receiving a measured current signal based on a measured electrical current from each of one or more electrode chips. At step 204, a current peak in the measured current signal is identified.

Background current in the measured current signal may be identified at step 206 and the background current may be deducted at step 208 from the measured current signal before identifying the current peak in the measured current signal at step 204.

At step 210, a peak intensity corresponding to the identified current peak is determined.

A concentration of a selected pollutant is determined at step 212 from a characterisation curve of the selected pollutant based on the determined peak intensity.

The steps for pollutant detection may be performed in respect of each of a plurality of selected pollutants simultaneously.

Examples

Referring now to FIGS. 4A through 4C, a test using a portable 16-channel analyser in accordance with an embodiment of the present invention for a raw sample will now be described. The portable 16-channel analyser was used for on-site test of Singapore solid waste (fly ash) for heavy metal ions, iodide, and total phenolic compounds.

After 30 minutes on-site leaching of heavy metal ions from the fly ash by a Institute of Materials Research and Engineering (IMRE)/Nanyang Technological University (NTU) home-developed ultrasonic-assisted tumbler, 9 parts of leachate were diluted with 1 part of buffer, that is, the dilution factor is set as 1.11. The mixtures were manually loaded to 16 cuvettes and SPEC chips were inserted into each cuvette for tests. After this, a “RUN” button was pressed for the portable analyser to auto-detect and display all results on a user interface as shown in FIG. 4B. Heavy metal ion marked as “UNDETECTED” means the leachate either has a concentration below the detection range of the analyser or there is no such heavy metal ion in the leachate. The “UNDETECTED” heavy metal ions are also marked as green, indicating a safe level in the sample. According to the on-site detection of the portable analyser, the fly ash sample does not contain any detectable heavy metal ions, iodide or total phenolic compounds, except Pb, Zn, Hg and Mo. The sample had a higher Pb concentration (18.732 ppm) than the 5 ppm cut-off for landfill so it failed a Pb test and this implies that the fly ash should be further treated to reduce Pb before landfill. Zn was also detected as 9.016 ppm in the sample, but as this is less than 10 ppm cut-off for landfill, the level of Zn is determined to be safe for landfill. Minimal amounts of Hg and Mo were also identified inside the sample: less than 0.02 ppm of Hg and less than 0.5 ppm of Mo. The analyser detected these elements, but at concentrations below the ranges of respective characterization curves.

The same fly ash leachate collected from the on-site test was also sent to a third- party accredited laboratory to be tested with standard testing equipment, namely inductively coupled plasma-optical emission spectrometer (ICP-OES). The standard test reported that 13.37 ppm of Pb and 7.24 ppm of Zn in the leachate, while other species of heavy metal ions were far below the cut-off levels for landfill.

The on-site detection results of the portable analyser have 40.1% higher of Pb and 24.5% higher of Zn than those of the standard test performed by the accredited laboratory. This deviation is mainly caused by heavy metal ion concentration difference in freshly prepared leachate (tested on-site by the portable analyser) and in leachate after storage for several days (sent to the accredited laboratory and tests completed after a week or so). After leaching, heavy metal ions may gradually precipitate over time. The precipitated heavy metal ions are aggregated, filtered, and thrown away before the ICP- OES test in the laboratory, which could cause the heavy metal ion concentrations tested after a few days to be lower than that of fresh leachates.

To verify this, NTU Nanyang Environment and Water Research Institute (NEWRI) laboratory freshly prepared a fly ash sample leachate and measured the heavy metal ions in the fresh leachate with ICP-OES. Freshly prepared fly ash leachate detection by ICP-OES at NTU NEWRI showed 16.3 ppm of Pb and 8.11 ppm of Zn in the fly ash sample and other species of heavy metal ions in the fly ash sample were also far below the cut-off levels for landfill. In this case, the measurement deviations between ICP-OES and the portable analyser using fresh leachates were 14.9% for Pb and 11.1% for Zn, respectively.

The ICP-OES test in the NTU NEWRI laboratory used a different portion of the fly ash sample than the on-site fly ash portion and the heavy metal ion distribution in different portions of the fly ash sample may not be uniform. Nevertheless, it may still be concluded that the portable heavy metal ion analyser is able to test for heavy metal ions on-site with reliable results.

The portable 16-channel analyser automatically generated a report for the solid waste leachate test as shown in FIG. 4C. The automatically generated report is valuable in authorized tests to avoid human intervention such as typo, editing, or modification caused report errors.

Based on the characterization curves saved in the library, the sensitivity and detection range for each analyte are summarized in Table 2 below.

Table 2. Singapore requirements on heavy metal concentrations and corresponding analyser detection range (Unit: ppb)

The portable multi-channel analyser and also the handheld one-channel analyser may set a detectable range for each channel equal to or slightly smaller than the detection ranges shown in FIGS. 1C through 1 F. Table 2 demonstrates that for all heavy metal ions, the analysers are more sensitive than the required criteria for Singapore landfill or public sewer. Thus, the analyser may be used to test landfill and sewage samples for heavy metal ions, iodide and total phenolic compounds.

Furthermore, the characterization curves and detection sensitivity ranges for the handheld one-channel analyser and the portable multi-channel analyser are the same, except for the different hardware and user interface design.

In conclusion, a handheld one-channel analyser and a portable 16-channel analyser have been developed based on electrochemical (EC) voltammetry to detect multiple species of analytes such as, for example, Ag(l), As(lll), Cd(ll), Cr(VI), Cu(ll), Fe(ll+lll), Mn(ll), Mo(VI), Ni(ll), Pb(ll), Sb(lll), V(V), Zn (II), Hg(ll), iodide and total phenolic compounds at sensitivities of between about 5 ppm and about 20 ppb. The handheld analyser may be used to detect different analytes one-by-one, while the multiple-channel analyser may be used to simultaneously detect multiple species of analytes in parallel.

Advantageously, the analysers of the present invention provide a boarder range of detectable ions including heavy metal ions, iodide and total phenolic compounds, altogether in a single device.

The analysers also have customized sensitivities for solid waste detection. Sensitivity may be improved by changing the EC recipes, such as by depositing ions on electrodes for a longer period of time. When more ions are reduced on the electrode surface, the detection becomes more sensitive. As sensitivity is also related to electrode size, screen-printed electrodes which are smaller, may be less sensitive. However, up to 1 to 5 ppb sensitivity (meeting the drinking water criteria) is achievable with screen- printed electrodes. A further advantage provided by the analyser of the present invention is fast ion detection. On-site detection helps save several days as compared to obtaining detection reports on multiple analytes using a laboratory instrument. Targeted heavy metal ion concentrations may be directly read out on the spot using the handheld analyser without requiring further manual data processing, allowing on-site decisions of solid waste disposal or wastewater discharge to sewer or watercourse to be made. The option of multiple-channels in parallel detection also increases detection speed by multiple times when the interested ions have multiple species. For example, a 16-channel analyser may take less than 30 minutes (min) to complete ion detections for sixteen (16) species, whereas it may take 2 to 3 hours to detect 16 ions one by one.

Cross-contamination may also be eliminated with the analysers of the present invention through use of one-time use SPECs or disposable SPECs. This helps prevent cross-contamination between different samples and avoids non-repeatability caused by poor cleaning of electrodes after each test.

Further advantageously, the analysers are easy for laymen to use due to a user- friendly interface and automation of measurements (after sample loading and sample type selection), data processing and report generation. After sample loading and sample type selection, a user may only need to press “RUN” button to obtain quantitative results as a report on concentrations of heavy metal ions and other pollutants (including iodide and total phenolic compounds) is auto-generated. Software with algorithms to process the EC data automatically and a touch-screen user interfaces may be provided with the analysers. Detection recipes and data processing software may be integrated as one piece of software.

The analysers of the present invention are also compact and lightweight, being standalone devices without requiring an external computer, and are significantly less costly to construct than commercially available analysers. The handheld one-channel analyser may be 14.6 cm by 7.8 cm by 6 cm with a mass of 430 g; the portable multiplechannel analyser may be 22 cm by 16.5 cm by 28.5 cm with a total mass of 4.33 kg (including a cuvette holder and a battery charger). The analysers are able to work as standalone devices with data process software integrated for direct on-site heavy metal ion concentration reading. The analysers may be applied for on-site detection applications in the following use cases: solid waste, contaminated soil, sediment and sludge; drinking water and industrial waste water; food and beverage; and mining.

While preferred embodiments of the invention have been described, it will be clear that the invention is not limited to the described embodiments only. Numerous modifications, changes, variations, substitutions and equivalents will be apparent to those skilled in the art without departing from the scope of the invention as described in the claims.

Further, unless the context clearly requires otherwise, throughout the description and the claims, the words "comprise", "comprising" and the like are to be construed in an inclusive as opposed to an exclusive or exhaustive sense; that is to say, in the sense of "including, but not limited to".

Claims

1 . An analyser for pollutant detection, comprising: one or more electrochemical detection units, wherein each of the one or more electrochemical detection units is configured to receive a control voltage signal according to a pollutant-specific detection protocol and output a measured current signal based on a measured electrical current from an electrode chip; one or more processors; a non-transitory computer-readable memory storing a detection protocol for each of a plurality of pollutants, a characterisation curve for each of the pollutants and computer program instructions executable by the one or more processors to perform operations for pollutant detection, the operations comprising: identifying a current peak in the measured current signal; determining a peak intensity corresponding to the identified current peak; and determining a concentration of a selected pollutant from the characterisation curve of the selected pollutant based on the determined peak intensity; and a display configured to display the concentration of the selected pollutant.

2. The analyser for pollutant detection according to claim 1 , wherein each of the one or more electrochemical detection units comprises a digital-to-analogue converter configured to convert a plurality of control voltages in the control voltage signal into a control voltage waveform for pollutant detection.

3. The analyser for pollutant detection according to claim 1 or 2, wherein each of the one or more electrochemical detection units comprises a current-to-voltage converter configured to convert the measured electrical current received from the electrode chip into a measured voltage waveform.

4. The analyser for pollutant detection according to claim 3, wherein each of the one or more electrochemical detection units further comprises an analogue-to-digital converter configured to convert the measured voltage waveform into a digital voltage signal.

5. The analyser for pollutant detection according to claim 4, wherein each of the one or more electrochemical detection units further comprises a microcontroller configured to convert the digital voltage signal into the measured current signal.

6. The analyser for pollutant detection according to any one of the preceding claims, wherein the operations for pollutant detection further comprise: identifying background current in the measured current signal; and deducting the background current from the measured current signal before identifying the current peak in the measured current signal.

7. The analyser for pollutant detection according to any one of the preceding claims, wherein the detection protocol for each of the pollutants comprises a screen-printed electrode chip (SPEC) specification, a detection buffer, a dilution factor, a voltammetry mode specification and parameter settings for a selected voltammetry mode.

8. The analyser for pollutant detection according to any one of the preceding claims, wherein the non-transitory computer-readable memory is further configured to store computer program instructions executable by the one or more processors to perform the operations for pollutant detection in respect of each of a plurality of selected pollutants simultaneously.

9. The analyser for pollutant detection according to any one of the preceding claims, further comprising a sample loader interfacing the electrochemical detection units, wherein the sample loader comprises a cuvette holder and a screen-printed electrode chip (SPEC) holder in a stacked arrangement.

10. The analyser for pollutant detection according to claim 9, wherein the sample loader further comprises a vibration motor attached to the cuvette holder.

11. A computer-implemented method for pollutant detection, comprising executing via one or more processors the steps of: receiving a measured current signal based on a measured electrical current from each of one or more electrode chips; identifying a current peak in the measured current signal; determining a peak intensity corresponding to the identified current peak; and determining a concentration of a selected pollutant from a characterisation curve of the selected pollutant based on the determined peak intensity.

12. The computer-implemented method according to claim 11 , further comprising: identifying background current in the measured current signal; and deducting the background current from the measured current signal before identifying the current peak in the measured current signal.

13. The computer-implemented method according to claim 11 or 12, further comprising performing the steps for pollutant detection in respect of each of a plurality of selected pollutants simultaneously.