A fully automated pH measurement system for 96-well microplates using a semiconductor-based pH sensor

Akira Yamada, Satoshi Mohri, Michihiro Nakamura, Keiji Naruse

Research output: Contribution to journalArticlepeer-review

23 Citations (Scopus)


The pH values of solutions have been commonly measured by glass electrodes, devices which respond on a time scale of minutes and require complicated operations such as calibration at every measurement. The development of a fast, automated pH measurement system for analytes in small volumes would be quite useful in many fields. Yet the practical application of such a device has been hampered by the need for rapid measurement and precise calibration. Our group has constructed a fully automated, self-calibrating pH measurement system capable of consecutively measuring 96 samples. The system uses a flow-through-type differential pH sensor probe based on a tiny, quickly responding pH-sensitive field-effect transistor (pH-FET) technology. The system was confirmed to measure the pH values of 26 μl solutions over a 135 s cycle (60 s for wash, 20 s for movement, 3 s for suction, and 52 s for measurement). The measurement error of multiple sample measurements, including measurements of solutions with low buffering capacity, was -0.0116 ± 0.0481 pH (average error ± S.D.). The high accuracy and high reproducibility of the results suggest that this automatic pH measurement system based on pH-FET can be applied for versatile uses.

Original languageEnglish
Pages (from-to)464-469
Number of pages6
JournalSensors and Actuators, B: Chemical
Issue number2
Publication statusPublished - Jan 7 2010


  • 96-Well microplate
  • Automation
  • Differential pH sensor probe
  • pH
  • pH-FET

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Instrumentation
  • Condensed Matter Physics
  • Surfaces, Coatings and Films
  • Metals and Alloys
  • Electrical and Electronic Engineering
  • Materials Chemistry


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