Development of analytical workflows for measurement of metal pollution in freshwater with citizen scientists

Sari, Mila

Abstract

The emergence of heavy metals, such as nickel (Ni2+) and zinc (Zn2+), as freshwater contaminant poses an environmental and public health risk. However, the current monitoring process lacks robustness and the spatiotemporal range, impeded by relatively complex and costly analytical processes. The need for a relatively simpler and rapid monitoring workflow for onsite metal monitoring drives this study in developing a two-step workflow detection system. The design of the workflow consisted of a simple, rapid, and onsite preconcentration method, followed by a microfluidic paper-based analytical device (μPAD) as a chemical sensor for target metal species.
Through this study, two μPADs for the detection of Ni2+ and Zn2+, separately, had been developed using a novel colorimetric reagent: 1,2-cyclohexanedione dioxime and 5-Br-PAPs, respectively. Which, the former had shown its potential as an alternative water-soluble colorimetric reagent for Ni2+ detection in μPAD, by improving the device fabrication step due to the use of water as a solvent. Both of the μPADs developed in this research had shown notable improvement in decreasing the reaction time, consequently producing results within 5 minutes after sample introduction. The μPADs also omitted the need for pipettes for sample introduction, since μPAD can safely be placed into a volume of sample instead. The Ni2+ detection using developed μPAD in this study allowed for detection down to 3 mg L-1 within 4 minutes, whereas Zn2+ detection using a second μPAD developed in this study achieved a 1 mg L-1 detection limit within 5 minutes.
A preconcentration workflow involving Lewatit MonoPlus SP 112 ion exchange resin in a cafetiere and 5 M NaCl as eluent, was also developed in this study, as means of simple, rapid, onsite preconcentration method. With the developed system, the resin was able to adsorb up to 60% and 80% of the initial Ni2+ and Zn2+ mass in the solution, respectively, within 5 minutes of plunging and mixing. This portable preconcentration system was then coupled with the developed μPADs for Ni2+ or Zn2+ detection, lowering the limit of detectionto 1 mg L-1 and 0.5 mg L-1 metal concentration, respectively. Through integration, the total duration of the workflow was set at 15 minutes, including preconcentration, elution, and sensing steps.
The developed workflow also emphasised accessibility and usability for citizen scientists as target users, considering simplicity, rapidness, and chemical hazards in its design. Upon initial review by 31 volunteers at the University of Hull, the developed workflow was regarded as simple and rapid by the users, showing the potential of the approach for water monitoring initiatives. However, further improvements in accessibility would be necessary to improve the analytical aspect of the workflow.

Citation

Sari, M. Development of analytical workflows for measurement of metal pollution in freshwater with citizen scientists. (Thesis). University of Hull. https://hull-repository.worktribe.com/output/4459145

• Thesis Type: Thesis
• Deposit Date: Nov 28, 2023
• Publicly Available Date: Nov 29, 2023
• Keywords: Chemistry
• Public URL: https://hull-repository.worktribe.com/output/4459145
• Additional Information: Department of Chemistry; University of Hull
• Award Date: Nov 14, 2023