Extended-range spectroscopic pH measurement using optimized mixtures of dyes

B. Raghuraman, G. Gustavson, R. E.G. Van Hal, E. Dressaire, O. Zhdaneev

Research output: Contribution to journalArticlepeer-review


The spectroscopic technique for pH measurement is a well-established laboratory technique that can give high-accuracy pH values. Recent studies have shown the advantage of this technique over standard potentiometric methods for pH measurements in fresh water and seawater and also at high temperatures and pressures. However, a limitation of the spectroscopic technique is that a single pH dye is sensitive only over a narrow pH range. We have developed optimized dye mixtures that are both sensitive and accurate over a broad pH range. The measurement is robust and simple, requires a minimum of two wavelengths, and is Independent of the volume of the dye mixture added. Optimization of the dye mixture formulation to maximize accuracy in a broad range of pH involves varying both the dye type and its mole fraction and also accounting for spectral noise. This technique has been successfully applied for in situ pH measurements of oilfield formation waters.

Original languageEnglish (US)
Pages (from-to)1461-1468
Number of pages8
JournalApplied Spectroscopy
Issue number12
StatePublished - Dec 2006


  • Extended-range pH
  • Spectroscopic pH
  • pH dye mixtures

ASJC Scopus subject areas

  • Instrumentation
  • Spectroscopy


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