A facile colorimetric assay for determination of salicylic acid in tobacco leaves using titanium dioxide nanoparticles†
A facile, colorimetric method for salicylic acid (SA) detection in tobacco leaves was developed using titanium dioxide nanoparticles (TiO2 NPs). The sensing strategy is based on the reaction of TiO2 NPs with SA at pH 5.5, which results in an intramolecular ligand to metal charge transfer transition between salicylate and Ti(IV) on the surface of TiO2 NPs, and causes the TiO2 NP solution to turn yellow. The TiO2 NP probe exhibits high selectivity for SA over seven structural chemicals (4-hydroxybenzoic acid, 3-hydroxybenzoic acid, benzoic acid, acetylsalicylic acid, phenol, methyl salicylate, and jasmonic acid). Moreover, the difference in the absorbance of the TiO2 NP solution is proportional to the concentration of SA over the range from 0.02 to 1.0 mM (R2 = 0.992). By using the TiO2 NP probe in 5 mM sodium acetate (pH 5.5) solutions, the limit of detection for SA was 15.4 μM at a signal-to-noise (S/N) ratio of 3. Furthermore, the practicality of the TiO2 NP probe was validated for the determination of SA in tobacco leaves by demonstrating its advantages including simplicity and selectivity.