Laser-Dye Imaging of the pH Field in a Laboratory Experiment

Satoshi Someya*, Shigeru Bando, Yongchen Song, Baixin Chen, Masahiro Nishio

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

2 Citations (Scopus)


We established a precise DeLIF (Dual Emission Laser Light Fluorescence) system for the instant measurement of the pH field in laboratory experiments. This method is very important in studies of the biological impacts of CO2 sequestration, i.e., effects of pH on organisms. The technique is demonstrated by applying it to the pH measurement around a liquid CO2 droplet, which has a large gradient of CO2 concentration near its interface, the concentration value on the boundary being known as the solubility of CO2. In the Laser Induced Fluorescence (LIF) method using quinine and an ultraviolet laser light source, the relatively unstable pulse of the laser source decreased the measurement reliability. We therefore investigated many kinds of fluorescent dye and demonstrated the DeLIF measurement, identifying a process for cancelling fluctuations of laser light intensity. Quinine and sulforhodamine were used as fluorescence dyes. The molar absorption coefficient and emission intensity of quinine depend on the pH of aqueous solutions, while those of sulforhodamine are not as much affected by pH. The ratio of these fluorescence intensities represents pH at each point of the image. As a result, the pH field was successfully measured with an uncertainty of only approximately ±0.005, for 3.0 < pH.

Original languageEnglish
Pages (from-to)789-795
Number of pages7
JournalJournal of Oceanography
Issue number4
Publication statusPublished - Aug 2004


  • Carbon dioxide
  • Dissolution
  • Flow visualization
  • Laser induced fluorescence
  • pH

ASJC Scopus subject areas

  • Oceanography


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