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Issue 4, 2019
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Fully inkjet-printed distance-based paper microfluidic devices for colorimetric calcium determination using ion-selective optodes

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Abstract

Although the determination of calcium ions (Ca2+) is of high importance to monitor water hardness, currently available devices for on-site analysis suffer from a lack of user-friendliness and sensitivity. This work demonstrates fully inkjet-printed and low-cost microfluidic paper-based analytical devices (μPADs) for the simple naked-eye colorimetric determination of calcium ions (Ca2+) in drinking and tap water samples. The quantification of Ca2+ relies on visual readout of the length of a colour-changed detection channel modified with ionophore-doped ion-selective optode nanospheres (nano-optodes), eliminating the requirement of a scanner or a camera. All fabrication steps for deposition of assay reagents have been performed by means of a simple desktop thermal inkjet printer, which is expected to contribute to highly batch-to-batch reproducible device preparation. The detectable Ca2+ concentrations between 0.05 mmol L−1 and 5 mmol L−1 cover the range recommended by the International Organization for Standardization (0.05–2.5 mmol L−1) and the World Health Organization (WHO) guideline for Ca2+ quantification in drinking water (less than 5 mmol L−1). The lowest concentration of Ca2+ detectable by the naked eye was found to be 0.05 mmol L−1, which is below the value achieved with previously reported paper-based devices. μPAD quantified Ca2+ concentrations in tap or drinking waters were within 15% error of the results obtained with a classical complexometric titration. Hence, distance-based μPADs relying on nano-optodes are sensitive and reproducible tools for equipment-free on-site assaying of Ca2+ in real samples.

Graphical abstract: Fully inkjet-printed distance-based paper microfluidic devices for colorimetric calcium determination using ion-selective optodes

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Supplementary files

Article information


Submitted
06 Nov 2018
Accepted
11 Dec 2018
First published
11 Dec 2018

Analyst, 2019,144, 1178-1186
Article type
Paper

Fully inkjet-printed distance-based paper microfluidic devices for colorimetric calcium determination using ion-selective optodes

H. Shibata, Y. Hiruta and D. Citterio, Analyst, 2019, 144, 1178
DOI: 10.1039/C8AN02146E

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