Fully inkjet-printed distance-based paper microfluidic devices for colorimetric calcium determination using ion-selective optodes. Issue 4 (18th December 2018)

• Record Type: Journal Article
• Authors: Shibata, Hiroyuki; Hiruta, Yuki; Citterio, Daniel
• Is Part Of: Analyst. Volume 144:Issue 4(2019)
• Page Start: 1178
• Page End: 1186
• Publication Date: 2018-12-18
• Subjects: Chemistry, Analytic -- Periodicals; 543
• DOI: 10.1039/c8an02146e
• Languages: English
• ISSNs: 0003-2654

Abstract

Abstract : Fully inkjet-printed and low-cost microfluidic paper-based analytical devices (μPADs) demonstrate the simple naked-eye colorimetric determination of calcium ions in drinking and tap water samples. Abstract : Although the determination of calcium ions (Ca 2+ ) 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 (Ca 2+ ) in drinking and tap water samples. The quantification of Ca 2+ 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 Ca 2+ 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 Ca 2+ quantification in drinking water (less than 5 mmol L −1 ). The lowest concentration of Ca 2+ 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 Ca 2+ 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 Ca 2+ in real samples.