A Reusable Eu 3+ Complex for Naked‐Eye Discrimination of Methanol from Ethanol with a Ratiometric Fluorimetric Equilibrium in Methanol/Ethanol Mixtures

Immediate naked eye distinction of methanol from ethanol can be performed by simple dissolution, in each of these solvents, of either [Na][EuFOD 4 ] ( 1 ) complex or in mixture of products from the reaction between [P 6,6,6,14 ][Eu(FOD) 4 ] and NaOPhMe 3 , referred as 2 , ([P 6,6,6,14 ] + = trihexyltetradecylphosphonium cation, FOD – = 1,1,1,2,2,3,3‐heptafluoro‐7,7‐dimethyloctane‐4,6‐dionate). Additionally, an easy, low‐cost, efficient and fast spectrofluorimetric method for the detection and quantification of methanol in mixtures with ethanol is described. This method is based on the changes in the Eu 3+ luminescence in the visible region due to the interaction of the [P 6,6,6,14 ][Eu(FOD) 4 ] complex with these alcohols. A limit of detection as low as 15 % (w/w) of methanol in mixtures of ethanol/methanol is discussed considering a linear calibration curve.