Microfluidic Paper-Based Analytical Device for Particulate Metals

Abstract

A microfluidic paper-based analytical device (μPAD) fabricated by wax printing was designed to assess occupational exposure to metal-containing aerosols. This method employs rapid digestion of particulate metals using microliters of acid added directly to a punch taken from an air sampling filter. Punches were then placed on a μPAD, and digested metals were transported to detection reservoirs upon addition of water. These reservoirs contained reagents for colorimetric detection of Fe, Cu, and Ni. Dried buffer components were used to set the optimal pH in each detection reservoir, while precomplexation agents were deposited in the channels between the sample and detection zones to minimize interferences from competing metals. Metal concentrations were quantified from color intensity images using a scanner in conjunction with image processing software. Reproducible, log-linear calibration curves were generated for each metal, with method detection limits ranging from 1.0 to 1.5 μg for each metal (i.e., total mass present on the μPAD). Finally, a standard incineration ash sample was aerosolized, collected on filters, and analyzed for the three metals of interest. Analysis of this collected aerosol sample using a μPAD showed good correlation with known amounts of the metals present in the sample. This technology can provide rapid assessment of particulate metal concentrations at or below current regulatory limits and at dramatically reduced cost.

Determination of Iron Ion in the Water of a Natural Hot Spring Using Microfluidic Paper-based Analytical Devices

“…The limit of quantification (LOQ) was estimated at 40 ppm, which was the minimum concentration that could be distinguished by the image processing software when the threshold of the color intensity was adjusted to the minimum value of zero, which was the intensity of the blank. The LOQ was comparable to that reported by Mentele et al 16 (1.5 μg in 30 μL, 50 mg L -1 ) while Asano et al found a lower LOQ (13.8 μM, 0.771 mg L -1 ) using a paper device with test spots where no diffusion happened since a single spot was used as a reservoir. 23 Thus, the spot-type paper device was preferable for enhancing the sensitivity, although the throughput was lowered since a sample had to be added to several spots for multiple measurements, which meant that Asano's device took four-times longer than either Mentele's or ours during the respective sample introductions.…”

“…4,5 μPADs have shown promise for their use in point-of-care testing during bioanalysis, as described in many publications. [6][7][8][9][10][11][12][13][14][15][16] When used in environmental analysis, μPADs have been successfully applied to the measurement of metal ions in particulate matters (PMs), [17][18][19] as well as being useful for measuring the oxidative activity of PMs. 20 We also reported the rapid use of μPADs in acid-base titrations during the on-site analysis of acidic water in a natural hot spring.…”

A Highly Structured 1,10-Phenanthroline Arrayed Hydrophobic Sulfone Membrane Platform for the Rapid Determination and Speciation of Fe2+/Fe3+ Ions in Water

“…The LOD obtained by our developed method was lower than that observed for a similar assay performed on μPADs. [16][17][18] Designing such devices was not only complex, but also required higher analyte volumes and longer durations for completion of the assay. On the other hand, our setup is easy with the one-step addition of the analyte to the reagent area/spot.…”

Practical High-Performance Lateral Flow Assay Based on Autonomous Microfluidic Replacement on a Film

“…Among POCT devices, paper-based devices have been seen as the ideal platform for point-of-care (POC) diagnostics due to their very low cost, simplicity, and inherent ability to wick fluids. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15] Fluid transport eliminates expensive pumping instrumentation and complicated handling. 16,17 The porous structure of paper is very convenient for dot-immunobinding assays, and cellulose itself has high affinity to biomolecules.…”