Optical pH Sensing in Milk: A Small Puzzle of Indicator Concentrations and the Best Detection Method

Optical chemical sensors can yield distinctively different responses that are dependent on the method applied for readout and evaluation. We therefore present a comprehensive study pH determined non-continuously with optical in real milk samples by either photometry or colorimetry (via RGB-readout of digital images) compared to values obtained electrochemically potentiometry. Additionally, photometric determination was conducted single-wavelength dual wavelength ratiometric evaluation absorbance. It found both precision accuracy benefit from lower concentrations bromocresol purple, which served as indicator inside sensor membrane. A further improvement is response. The colorimetric evaluation, however, gain if higher concentration immobilized This has major impact future fabrication membranes because they be better tuned match most precise accurate range planned detection method.