Utilization of the dye N-methyl-6-oxyquinolone as an optical acidometer in molecular solvents and protic ionic liquids.

We developed a procedure to use the highly sensitive dye N-methyl-6-oxyquinolone as an acidity probe in molecular solvents and protic ionic liquids. The combination of well-established stationary UV-vis absorption and the mathematical algorithm of singular value decomposition allows the determination of the amount of acidic protons even in complex solvents like ionic liquids.