Analysis of organic acids and phenols of interest in the wine industry using Langmuir–Blodgett films based on functionalized nanoparticles

• Published in: Analytica chimica acta 2015-01, Vol.853, p.572-578
• Main Authors: Medina-Plaza, C., García-Cabezón, C., García-Hernández, C., Bramorski, C., Blanco-Val, Y., Martín-Pedrosa, F., Kawai, T., de Saja, J.A., Rodríguez-Méndez, M.L.
• Format: Article
• Language: English
• Subjects: Caffeic Acids - analysis; Catalysis; Electrochemical Techniques; Electrodes; Electrolytes - chemistry; Gallic Acid - analysis; Gold; Gold - chemistry; Gold nanoparticle; Langmuir–Blodgett; Metal Nanoparticles - chemistry; Nanoparticles; Organic acids; Phenolic acids; Phenolic compounds; Phenols; Phenols - analysis; Sensors; Wine - analysis; Wines
• ISSN: 0003-2670; 1873-4324
• DOI: 10.1016/j.aca.2014.10.046

[Display omitted] •For the first time functionalized NPs immobilized in LB films have been used as voltammetric sensors.•Films showed excellent electrocatalytic properties toward phenols and acids found in wines.•Improved performance is due to combination of electrocatalytic NPs with the high surface/volume of LB films.•The potential applications in the wine industry have been evidenced. A chemically modified electrode consisting of Langmuir–Blodgett (LB) films of n-dodecanethiol functionalized gold nanoparticles (SDODAuNP-LB), was investigated as a voltammetric sensor of organic and phenolic acids of interest in the wine industry. The nanostructured films demonstrated interfacial properties being able to detect the main organic acids present in grapes and wines (tartaric, malic, lactic and citric). Compared to a bare ITO electrode, the modified electrodes exhibited a shift of the reduction potential in the less positive direction and a marked enhancement in the current response. Moreover, the increased electrocatalytic properties made it possible to distinguish between the different dissociable protons of polyprotic acids. The SDODAuNP-LB sensor was also able to provide enhanced responses toward aqueous solutions of phenolic acids commonly found in wines (caffeic and gallic acids). The presence of nanoparticles increased drastically the sensitivity toward organic acids and phenolic compounds. Limits of detection as low as 10−6molL−1 were achieved. Efficient catalytic activity was also observed in mixtures of phenolic acid/tartaric in the range of pHs typically found in wines. In such mixtures, the electrode was able to provide simultaneous information about the acid and the phenol concentrations with a complete absence of interferences. The excellent sensing properties shown by these sensors could be attributed to the electrocatalytic properties of the nanoparticles combined with the high surface to volume ratio and homogeneity provided by the LB technique used for the immobilization. Moreover, the LB technique also provided an accurate method to immobilize the gold nanoparticles giving rise to stable and reproducible sensors showing repeatability lower than 2% and reproducibility lower than 4% for all the compounds analyzed.