Mercury (Hg) is a toxic element which impacts on biological systems and ecosystems. Because the toxicity of Hg species is highly dependent on their concentration levels and chemical forms, the sensitive identification of the chemical forms of Hg—i.e., Hg speciation—is of major significance in providing meaningful information about the sources of Hg exposure. In this study, a microfluidic-based device made of high-clarity poly(methyl methacrylate) (PMMA) was fabricated. Then, titanium dioxide nanoparticles (nano-TiO₂s) were attached to the treated channel’s interior with the aid of poly(diallyldimethylammonium chloride) (PDADMAC). After coupling the nano-TiO₂-coated microfluidic-based photocatalyst-assisted reduction device (the nano-TiO₂-coated microfluidic-based PCARD) with high-performance liquid chromatography (HPLC) and inductively coupled plasma mass spectrometry (ICP-MS), a selective and sensitive, hyphenated system for Hg speciation was established. Validation procedures demonstrated that the method could be satisfactorily applied to the determination of mercury ions (Hg²⁺) and methylmercury ions (CH₃Hg⁺) in both human urine and water samples. Remarkably, the zeta potential measured clearly indicated that the PDADMAC-capped nano-TiO₂s with a predominance of positive charges indeed provided a steady force for firm attachment to the negatively charged device channel. The cause of the durability of the nano-TiO₂-coated microfluidic-based PCARD was clarified thus.

Mercury (Hg) is a toxic element impacting on biological systems and ecosystems. Because the toxicity of Hg species is highly dependent on concentration levels and chemical forms, sensitive identification of chemical forms for Hg, i.e., Hg speciation, is of major significance in providing meaningful information about the source of Hg exposure. In this study, a microfluidic-based device made of high clarity poly(methyl methacrylate) (PMMA) was fabricated. Then titanium dioxide nanoparticles (nano-TiO2) were attached to the treated channel interior with the aid of poly(diallyldimethylammonium chloride) (PDADMAC). After coupling the nano-TiO2-coated microfluidic-based photocatalyst-assisted reduction device (the nano-TiO2-coated microfluid-ic-based PCARD) with high-performance liquid chromatography (HPLC) and inductively coupled plasma-mass spectrometry (ICP-MS), a selective and sensitive hyphenated system for Hg specia-tion was established. Validation procedures demonstrated that the method could be satisfactorily applied to the determination of mercuric ion (Hg2+) and methylmercury ion (CH3Hg+) in both human urine and water samples. Remarkably, the zeta potential measured clearly indicated the PDADMAC-capped nano-TiO2 with predominance of positive charges indeed provided steady force for firm attachment to the negatively charged device channel. The cause for the durability of the nano-TiO2-coated microfluidic-based PCARD was clarified thus.

Various analytical methods for water quality monitoring have been standardized to date; however, implementation of these techniques necessitates considerable skill or expensive equipment, which impacts their use. In this study, a pragmatic strategy that employs an open-source Arduino platform coupled with visible-spectrum colorimetry for water quality assessment is proposed. Validation procedures demonstrate satisfactory application of the developed system to determine free residual chlorine (frCl) and ammonia–nitrogen (NH₃–N) in collected water samples. The detection limits achieved, i.e., 0.04 and 0.03 mg L^–1 for frCl and NH₃–N, respectively, are considerably lower than the concentration levels recommended by regulations; thus, the proposed technique has sufficient detection capability for common use. Moreover, on-site water quality assessment can be achieved using a compact configuration, as the system weighs less than 100 g and is powered by a laptop. Remarkably, the system constructed in this study is more cost-effective than commercially available spectrophotometers, at approximately USD 35 per system.