Supporting Information

Advances in Imaging-Assisted Sensing Techniques for Heavy Metals in Water:

Trends, Challenges, and Opportunities

Rishabh Jain,1,2 Anupma Thakur,1,2 Pahuljot Kaur,1 Ki-Hyun Kim,3* and Pooja Devi1,2,*

1CSIR-Central Scientific Instruments Organisation, Chandigarh-160030, India2Academy of Scientific and Innovative Research (AcSIR), Ghaziabad- 201002, India

3Department of Civil & Environmental Engineering, Hanyang University, Korea

Table 1S. Mobile applications on imaging-assisted quantifications

Order Application Name

Developer Name

Android/IOS

Paid /Free Sensing Parameters Additional Features Reference

A. Mobile Apps for General Water Parameter Quantification1. SAM1- Smart

Aqua Meter Sensorex IOS Free pH, oxidation-reduction potential (ORP),

conductivity/ TDS, and temperature.Records time, date, and GPS coordinates, email facility

[1]

2. Aquachek Smart

Hach Company IOS Free Chlorine and bromine Water volume calculator,email facility

[2]

3. HTH® Test To Swim® Water Testing App

HTH Pools Android Free Total chlorine, bromine, pH, total alkalinity, total hardness, and cyanuric acid

Permits to test up to 100 times with only 1 kit

[3]

4. Insta Link Home

Ltpcs Tech Dev Android Free Free chlorine, bromine, total chlorine, pH, alkalinity, cyanuric acid, hardness, copper, and salt

Employs testified test-strips for sensing

[4]

5. Pool Doctor John Gazzini IOS Free Free chlorine, pH, calcium hardness, and stability

- [5]

6. Pool Care Zac Lippard Android Free Chlorine, pH, calcium hardness, stabilizer/conditioner, salt, phosphates, etc.

- [6]

7. Pool Boy Pro Jose Weeks IOS Paid pH, calcium, hardness, temperature, phosphates, copper, iron, etc.

- [7]

8. Pool Guy Pro Jayaruwan Mannapperuma

Android Paid Free chlorine, calcium hardness, pH, salt level total alkalinity, dry acid, muriatic acid

- [8]

9. Pool Monitor iCatStudios Android, IOS

Paid Free chlorine, total chlorine, calcium hardness, pH, salt level total alkalinity, temperature, cynauric acid, combined chlorine, saturation, chlorine source

- [9]

10. Pool Kit Smart Apps Android Free Free chlorine, cynauric acid, pH, total alkalinity, borate, calcium hardness

- [10]

11. Clorox Pool Digital Pool Android Free Free chlorine, total chlorine pH, total alkalinity and stability

Offers liquid test-strip testing

[11]

12. Pool Cloud John Gazzini IOS Free Free chlorine - [12]

13. Pool Pal Pirates Love Bacon

Android Free Water temperature, pH, free chlorine, total alkalinity, calcium hardness, salt, borates

- [13]

14. MQuant® StripScan

Sigma-Aldrich IOS Paid pH, concentrations of chemicals (heavy metals)

Provides reliable quantification of water, food & beverage samples

[14]

B. Mobile Apps for Heavy Metal Quantification1. Mobosens University of

IllinoisIOS Paid Nitrates, heavy metals, pathogens Broadcast water sensing

information via GPS and mobile broadband

[15]

2. Light meter application

Xiao, Yu - - Chromium ions Broadcast sensing information, Linear dynamic range of 0.8-50 ppb with the detection limit of 0.81 ppb

[16]

3. CAnal MeelapsomJarujamrus

Android - Mercuryions

Broadcast sensing information, LDR: 0.01 to 100 ppm;LOD: 3 ppb

[17]

Table 2S. Commercial kits available for heavy metal quantifications

Order Commercial kit

CompanyKit Type; Analyte; Concentration Range

A. Commercial kits for General Water Parameter Quantification1. Test Strips, MQuant™

MerckPaper-based; available for general water parameters (chlorine, peroxide, glucose, carbonate hardness)

[18]

2. Colorimetric and Titrimetric Test KitsMerck

Solution-based; available for general water parameters (ozone, hydrazine, peroxide, glucose)

[19]

B. Commercial kits for Heavy Metal Quantification3. Test Strips, MQuant™

MerckPaper-based; available for heavy metals (lead, arsenic, iron, nickel, zinc) [18]

4. Heavy Metal Test Kit Vitality Plus Australia

Solution-based; cadmium, cobalt, copper, iron, lead, mercury, nickel, zinc, manganese; ppb to ppm

[20]

5. Water Metals Test Kit Filter Water

Paper-based; cadmium, cobalt, copper, iron, lead, mercury, nickel, zinc; 10 ppb to 1 ppm

[21]

6. Heavy Metal Test Kit Osumex Natural Alternatives Ltd.

Solution-based; cadmium, cobalt, copper, iron, lead, mercury, nickel, zinc, manganese; ppb to ppm

[22]

7. Heavy Metal Test Kit TestAssured, USA

Paper-based; cadmium, cobalt, copper, iron, lead, mercury, nickel, zinc, manganese; 10 ppb to 1 ppm

[23]

8. Heavy Metal Test Kit Schneider Labs, USA

Solution-based; arsenic, cadmium, cobalt, copper, chromium, hexavalent chromium, mercury, lead, and thallium; 10 ppb to 1 ppm

[24]

Order Commercial kit

CompanyKit Type; Analyte; Concentration Range

9. eXact iDip® Photometer Industrial Test Systems, Inc.

Paper- and device-based; cadmium, cobalt, copper, iron, lead, mercury, nickel, zinc; digital ppb-level testing

[25]

10. TotalCARE Heavy Metal Test Kit MicroWaterman

Solution-based; cadmium, cobalt, copper, iron, lead, mercury, nickel, zinc, manganese; ppb to ppm

[26]

11. GHM-01 Detector for Common Heavy Metals Appealing Products, Inc.

Solution-based; iron, nickel, zinc, cadmium, cobalt, copper, mercury, lead, and thallium; ppb to ppm

[27]

12. WG 34 Heavy Metal Detection Kit Westminster International Ltd, UK

Paper-based; cadmium, thallium, mercury, and lead; ppb to ppm [28]

13. Iron Test KitCHEMetrics

Solution-based; Iron; 1 to 10 ppm [29]

14. NECi Colorimetric Nitrate Water Test KitCole Parmer

Solution-based; nitrates; 1 to 10 ppm [30]

15. SenSafe® Water Metals Check Industrial water systems

Solution-based; cadmium, cobalt, copper, iron, lead, mercury, nickel, and zinc; ppb to ppm

[31]

16. Chlorine test kit (HI3831F),Nitrite test kit (HI3873), Nitrate test kit (HI3874) and Copper test kit (HI3847)

Hanna InstrumentsSolution-based; chlorine, nitrite, nitrate, copper; ppb to ppm [32]

17. Orion™ AQUAfast AQ4000 Colorimeter with test-strips Thermo Fisher Scientific

Paper-based; cyanide, fluoride, nitrite, nitrate, chloride, iodide, bromide, sulfide, ammonia, zinc, phosphate and sulfate; ppb to ppm

[33]

Figure 1S. Illustration of PMMA-based sensing platform: (A) preparation of PMMA ink from polymer sheets, (B) preparation of hydrophobic pen and fabrication of paper-based optical assay plate, (C) enlarged presentation of producing microzones and behavior of dyed water droplets within the hydrophobic barriers, and (D) optical assay plate with shapes drawn by hydrophobic pen and their associated SEM images (Adapted from Ref. [32]).

Figure 2S. Presentation of colorimetric assay procedures for Hg ions: (A) smartphone-assisted colorimetric analyzer and (B) calibration curves plotted for gray intensity values vs. Hg(II) concentration (Adapted from Ref. [48]).

Figure 3S. Schematic of UC-LRET sensing system: (A) mechanism for Hg(II) detection, (B) emission response recorded for various concentrations of Hg(II) ions, and (C) images showing colorimetric response of sensors toward various concentrations of Hg(II) ions and interfering ions (Adapted from Ref. [65]).

Figure 4S. Multi-element heavy metal paper sensor: (A) fabrication method of 3D paper-based microfluidic chips and changes in color with different metal ions; (B) fluid moving assay in the paper chips and comparison of color intensities of front and back side of chip; and (C) schematic representation of sensing procedure using 3D paper-based microfluidics (Adapted from Ref. [11]).

Figure 5S. PAD-based sensing application for heavy metals: (A) Illustration of fabrication of PAD and its sensing abilities; and (B) PAD-based analysis of Pb(II) and the effect of interfering ions (Adapted from Ref. [21]).

References

[1] Sensorex, SAM-1 Smart Aqua Meter Sensor Interface for Apple & Android Devices.[2] H. Company, AquaChek Smart [3] H. Pools, hth® Test to Swim® water testing app.[4] L. Chemical, Insta-LINK Home.[5] J. Gazzini, Pool Doctor.[6] Z. Lippard, Pool care.[7] J. Weeks, Pool Boy Pro.[8] J. Mannapperuma, Pool Guy Pro.[9] iCatStudios, Pool Monitor.[10] S. apps, Pool kit.[11] D. Pool, Clorox Pool.[12] J. Gazzini, Pool Cloud.[13] P.L. Bacon, Pool Pal.[14] M. StripScan, MQuant® StripScan, Digital test strip readout, Sigma-Aldrich.[15] L. Liu, MoboSens.[16] S. Yu, W. Xiao, Q. Fu, Z. Wu, C. Yao, H. Shen, Y. Tang, Analytical Methods 8 (2016) 6877.[17] P. Jarujamrus, R. Meelapsom, S. Pencharee, A. Obma, M. Amatatongchai, N. Ditcharoen, S. Chairam, S. Tamuang, Analytical Sciences 34 (2018) 75.[18] Merck, Test Strips, MQuant™.[19] Merck, Colorimetric Test Kits.[20] VitalityPlus, Heavy Metal Test Kit.[21] Filterwater, Water Metals Test Kit.[22] Osumex, HEAVY METALS TEST KITS.[23] TestAssured, HEAVY METALS TEST STRIPS.[24] S. Laboratories, Heavy Metals Test Kit.[25] I.T. Systems, eXact iDip® Smart Photometer System®.[26] MicroWaterman, TotalCARE Heavy Metal Screen Test.[27] A. Products, GHM-01 Detector.[28] Westminster, WG 34 Heavy Metal Detection Kit.[29] CHEMetrics, Iron Test Kit.[30] C. Parmer, NECi Colorimetric Nitrate Water Test Kit.[31] SenSafe®, SenSafe® Water Metals Check.[32] H. Instruments, Colorimetric chemical kits.[33] T.F. Scientific, Orion™ AQUAfast AQ4000 Colorimeter