Inkjet-printed pH-independent paper-based calcium sensor with fluorescence signal readout relying on a solvatochromic dye

Hiroyuki Shibata, Yuma Ikeda, Yuki Hiruta, Daniel Citterio

Research output: Contribution to journalArticlepeer-review

8 Citations (Scopus)


A challenge for paper-based cation sensors relying on classical carrier-based ion-selective optodes (ISOs) is their pH-cross response caused by the use of H+-sensitive chromoionophores as optical signal transducers. This work demonstrates fully pH-independent fluorescence-based calcium detection with a paper-based plasticizer-free ISO. To achieve a pH-independent assay, a solvatochromic dye (SD) instead of a traditional H+-sensitive chromoionophore has been applied to the paper-based ISO by means of inkjet printing technology. The detection principle depends on an ionophore-driven phase-transfer ion-exchange reaction between target cations and the positively charged SD, which no longer involves H+ in the optical signal transduction process. The developed paper-based ISOs with the SD resulted in Ca2+ concentration-dependent response curves not affected by the sample pH (pH 6.0, 7.0, and 8.0). The dynamic range obtained for Ca2+ detection was from 10−5 to 1 mol L−1 with a detection limit of 19.3 μmol L−1. Additionally, excellent selectivity derived from the used ionophore has been confirmed. As a simple practical application, the determination of Ca2+ in mineral water has been achieved without the pH-buffering process required for conventional cation-exchange ISOs.

Original languageEnglish
Pages (from-to)3489-3497
Number of pages9
JournalAnalytical and bioanalytical chemistry
Issue number14
Publication statusPublished - 2020 May 1


  • Calcium ion sensing
  • Fluorescence detection
  • Inkjet printing technology
  • Ionophore-based ion-selective optodes
  • Paper-based analytical devices
  • Solvatochromic dyes

ASJC Scopus subject areas

  • Analytical Chemistry
  • Biochemistry


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