Extended-range spectroscopic pH measurement using optimized mixtures of dyes

Area of Science:

• Analytical Chemistry
• Environmental Science
• Geochemistry

Background:

• Spectroscopic pH measurement is a high-accuracy laboratory technique.
• It offers advantages over potentiometric methods in various conditions, including fresh water, seawater, high temperatures, and pressures.
• A key limitation is the narrow pH range sensitivity of single pH dyes.

Purpose of the Study:

• To develop optimized dye mixtures for spectroscopic pH measurement with broad pH range sensitivity and accuracy.
• To create a robust and simple spectroscopic pH measurement technique.
• To apply the developed technique for in situ pH measurements in oilfield formation waters.

Main Methods:

• Formulation of optimized dye mixtures by varying dye type and mole fraction.
• Optimization to maximize accuracy and account for spectral noise.
• Development of a measurement protocol requiring a minimum of two wavelengths, independent of dye volume.

Main Results:

• Developed dye mixtures demonstrate sensitivity and accuracy over a broad pH range.
• The spectroscopic method is robust and simple to implement.
• Successful application for in situ pH measurements of oilfield formation waters.

Conclusions:

• Optimized dye mixtures overcome the narrow pH sensitivity limitation of single-dye spectroscopic methods.
• The developed spectroscopic technique provides accurate and robust pH measurements in diverse and challenging environments.
• This advancement is particularly valuable for in situ measurements in applications like oilfield exploration.