Microfluidic paper-based analytical devices (μ-PADs) fabricated in Japan were employed for the determination of total chromium (Cr) in water, soil, and lettuce irrigated with wastewater in Ethiopia. The μ-PADs, which were printed by wax printing in Japan, were transported to Ethiopia followed by preparation for the determination of total Cr by adding appropriate reagents to the pretreatment and detection zones. Soil and lettuce samples were determined by the μ-PADs and a UV-Vis spectrophotometer in Ethiopia. The paired t-test showed that the mean total Cr concentrations determined in the soil and lettuce samples were not significantly different between μ-PADs and UV-Vis spectrophotometric analysis at the 5% level of significance. This implies that the μ-PADs has good accuracy and reliability and could be employed to monitor Cr in environmental samples. We found that the total Cr concentrations in all soil and lettuce samples were above the permissible limit. Moreover, the evaluation of Cr contamination level using the geo-accumulation index indicated that the soils are contaminated with Cr moderately to heavily. Thus, the present work successfully demonstrated the potential remote investigation of pollution in a less-equipped laboratory by transporting the μ-PADs fabricated in another laboratory.
Speciation of chromium (Cr) was demonstrated using microfluidic paper-based analytical devices (μ-PADs) that permit the colorimetric determination of hexavalent chromium (Cr(VI)) and trivalent chromium (Cr(III)) via online oxidation. The μ-PADs consist of left and right channels that allow the simultaneous measurements of Cr(VI) and total Cr based on the colorimetric reaction of Cr(VI) with 1,5-diphenylcarbazide (DPC). For the determination of Cr(VI), a sample solution was directly reacted with DPC in the left channels whereas total Cr was determined in the right channels, which permitted online oxidation in the pretreatment zone containing cerium (IV) (Ce(IV)) followed by a colorimetric reaction with DPC. We found that the online oxidation of Cr(III) proceeded 100% whereas Ce(IV) inhibited the reaction of Cr(VI) with DPC. Therefore, speciation can be achieved by measuring the Cr(VI) and total Cr in the left and right channels followed by the subtraction of Cr(VI) from total Cr. The limits of detection and quantification were 0.008 and 0.020 µg mg L -1 for Cr(VI) and 0.07 and 0.1 mg L -1 for Cr(III) or total Cr, respectively. The linear dynamic ranges were 0.02-100 mg L -1 and 0.1-60 mg L -1 for Cr(VI) and Cr(III), respectively. The RSDs were less than 7.5%. The results obtained using μ-PADs were in good agreement with those obtained via ICP-OES with recoveries of 92-108% for Cr(III) and 108-110% for Cr (VI) using μ-PADs, and 106-110% for total Cr using ICP-OES. Thus, the μ-PADs could potentially be utilized for the speciation of chromium in developing countries where environmental pollution and the availability of sophisticated instruments are significant problems.
The present study was focused on improving sensitivity to trace levels of Cu(II) by subjecting microfluidic paper-based analytical devices (μ-PADs) to a preconcentration process via coprecipitation using aluminum hydroxide. The experimental conditions were optimized for the pH of the coprecipitation, centrifugation, and amounts of reagents that were deposited onto µ-PADs for Cu(II) assay. The resultant limit of detection reached as low as 0.003 mg L -1 with a linear range of 0.01-2.00 mg L -1 . The relative standard deviations for intra-and inter-day precision were 3.2 and 4.6%, respectively (n = 9). Spiked water samples were analyzed using the μ-PADs after coprecipitation preconcentration. The results were verified by comparing them with those of inductively coupled plasma-optical emission spectrometry (ICP-OES).Recoveries ranged from 97.1-104% and from 98.7-105% using the present method and ICP-OES, respectively. These results suggest that the simple, highly sensitive, and inexpensive proposed method would be helpful for analyzing trace levels of Cu(II) in water samples in poorly equipped laboratories.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.