Low-Cost Analytical Tools for Particulate Matter Composition Analysis
" Particulate matter (PM) is the biggest factor in air pollution problem contributing to 4 million deaths annually reported by Global Burden of Disease (GBD). The toxic chemical compositions in PM such as trace metals, reactive oxygen species, and organic compounds cause DNA oxidative damage and carcinogenic mechanism in respiratory and cardiovascular systems in human body. This work presents low-cost, portable, and disposable electrochemical devices for analyzing trace metals including Zn, Cd, Pb, Co, and Ni in PM. The device was fabricated using carbon ink stencil-printed on a low-cost polyethylene transparency (PET) sheet to create carbon stencil-printed electrode (CSPE). For Zn, Cd, and Pb simultaneous detection, electrospraying AgNP was chosen for electrode modification. Dispersive AgNP on electrode surface was observed resulting in increase of surface area. In addition, Bi and Nafion were used as the co-modifiers to enhance current signal. Moreover, acetate buffer pH 5.0 was the suitable condition to obtain the best limit of detection (LOD). AgNP/Bi/Nafion modified CSPE provided LOD of 5.0, 0.5, and 0.1 μg L-1 for Zn, Cd, and Pb detection, respectively. The proposed method was used to measure Zn, Cd, and Pb simultaneously in aerosol samples collected from Fresno, Califonia by using the
wearable personal air sampler. The results showed a few samples contained Zn ranging from 0.04-1.41 ng m-3 and one sample contained 0.2 ng m-3 Pb. The results from the proposed method were not significantly different from the results measured using ICP-MS at 95% confidence. Besides CSPE developed for Zn, Cd, and Pb detection in PM, it was also used for Co and Ni analysis because these metals tend to produce reactive oxygen species into the air via Fenton-like reaction. CSPE for Co and Ni determination was modified with Bi due to the ability of Bi to form amalgam with metals assisting to enhance current signal. Furthermore, dimethylglyoxime (DMG) was used as a Co(II) and Ni(II) chelator with highly selective chemical precipitation for adsorptive stripping voltammetry. The developed approach gave LOD of 1.0 and 5.0 μg L -1 for Co and Ni, respectively. In the real application, Bi modified CSPE was used to determine Co in Co aerosol samples and Ni in welding fume samples. The amount of Co and Ni in the samples determined using the proposed method was not significantly different from the results validated using ICP-MS at 95% confidence. Incidentally, complicated compounds found in PM such as organic compounds are difficultly determined with simple on-site analysis. Therefore, this work proposed another portable, low-cost, and simple tool that integrated the separation function using electrophoresis into microfluidic paper-based analytical device for complicated samples analysis. Colorimetry and fluorescence were used as the detection methods for
investigating the system. Chlorophenol red and indigo carmine were used as the model analytes for colorimetric detection. The parameters affecting to the separation were paper types, channel width, and applied potential. Addition of injection part into the device improved resolution and reduce peak broadening of the separation. For fluorescence detection, the determination of %conjugation between fluorescein isothiocyanate (FITC) and glutamic acid was the application for demonstrating the system. In conclusion, the low-cost methods for PM analysis were proposed with using CSPE to detect Zn, Cd, Pb, Ni and Co and using electrophoresis separation on mPAD prepared for effective complicated compounds analysis in the future. "
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