Question

What pH indicators are commonly used for non-polar medium?

Answer 1

Compounds, commonly used as pH-indicators, are soluble in aqueous media and polar solvents (DMSO, DMF, NMP etc.) and are functional pretty much across all these solvents. However, practically none these indicators are soluble in non-polar solvents (hexane, chloroform, dioxane etc.).

I briefly searched for the suitable available systems and so far there is only an article about oxoporphyrinogen derivatives used as pH-indicators in CH2Cl2CHX2ClX2 [1]. Are there any other common substances that are typically used for the visualization of acid-base equilibrium in solvents with low polarity?