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

Hiroyuki Shibata, Yuki Hiruta, Daniel Citterio

Research output: Contribution to journalArticle

10 Citations (Scopus)


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.

Original languageEnglish
Pages (from-to)1178-1186
Number of pages9
Issue number4
Publication statusPublished - 2019 Feb 21


ASJC Scopus subject areas

  • Analytical Chemistry
  • Biochemistry
  • Environmental Chemistry
  • Spectroscopy
  • Electrochemistry

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