Chromogenic signalling of water content in organic solvents by hydrazone–acetate complexes

New chromogenic probe systems for the signalling of the water content in representative water-miscible organic solvents (acetonitrile and tetrahydrofuran) were investigated. The effect of the water content in organic solvents on the complex formation of hydrazone dye with acetate ions was utilized for the signalling. The hydrazone–acetate system exhibited a pronounced chromogenic signalling behaviour that could be detected by eye in response to the changes in water content in such common water-miscible organic solvents as acetonitrile and tetrahydrofuran. Prominent colour changes were observed for up to 1 and 2% water content in acetonitrile and THF, respectively. Detection limits of the anthracene-based hydrazone–acetate system for determination of the water content in acetonitrile and tetrahydrofuran were 0.037 and 0.071%, respectively. The 7-hydroxycoumarin-based hydrazone–acetate system showed somewhat less sensitive signalling behaviour, with respective detection limits of 0.12 and 0.63% in acetonitrile and tetrahydrofuran. The designed hydrazone–acetate systems could be used as a simple and convenient chromogenic probes for the determination of the water content in representative organic solvents of acetonitrile and tetrahydrofuran.

► New chromogenic probe for the water content in organic solvents was devised.
► Effect of water content on the hydrazone–acetate complex was used for the signalling.
► Pronounced chromogenic behaviour as a function of water % was observed.
► Prominent signallings were observed up to 1 and 2% water in acetonitrile and THF.