Chelate titrations of Ca2+ and Mg2+ using microfluidic paper-based analytical devices

Shingo Karita, Takashi Kaneta

Research output: Contribution to journalArticlepeer-review

57 Citations (Scopus)


We developed microfluidic paper-based analytical devices (μPADs) for the chelate titrations of Ca2+ and Mg2+ in natural water. The μPAD consisted of ten reaction zones and ten detection zones connected through narrow channels to a sample zone located at the center. Buffer solutions with a pH of 10 or 13 were applied to all surfaces of the channels and zones. Different amounts of ethylenediaminetetraacetic acid (EDTA) were added to the reaction zones and a consistent amount of a metal indicator (Eriochrome Black T or Calcon) was added to the detection zones. The total concentrations of Ca2+ and Mg2+ (total hardness) in the water were measured using a μPAD containing a buffer solution with a pH of 10, whereas only Ca2+ was titrated using a μPAD prepared with a potassium hydroxide solution with a pH of 13. The μPADs permitted the determination of Ca2+ and Mg2+ in mineral water, river water, and seawater samples within only a few minutes using only the naked eye-no need of instruments.

Original languageEnglish
Pages (from-to)60-67
Number of pages8
JournalAnalytica Chimica Acta
Publication statusPublished - Jun 14 2016


  • Calcium
  • Chelate titration
  • Hardness
  • Magnesium
  • Microfluidic paper-based analytical device
  • Natural water

ASJC Scopus subject areas

  • Analytical Chemistry
  • Biochemistry
  • Environmental Chemistry
  • Spectroscopy


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