Pencil graphite electrodes for improved electrochemical detection of oleuropein by the combination of Natural Deep Eutectic Solvents and graphene oxide

Abstract

A novel methodology is presented for the enhanced electrochemical detection of oleuropein in complex plant matrices by Graphene Oxide Pencil Grahite Electrode (GOPGE) in combination with a buffer modified with a Natural Deep Eutectic Solvent, containing 10% (v/v) of Lactic acid, Glucose and H2O (LGH). The electrochemical behavior of oleuropein in the modified‐working buffer was examined using differential pulse voltammetry. The combination of both modifications, NADES modified buffer and nanomaterial modified electrode, LGH‐GOPGE, resulted on a signal enhancement of 5.3 times higher than the bare electrode with unmodified buffer. A calibration curve of oleuropein was performed between 0.10 to 37 μM and a good linearity was obtained with a correlation coefficient of 0.989. Detection and quantification limits of the method were obtained as 30 and 102 nM, respectively. In addition, precision studies indicated that the voltammetric method was sufficiently repeatable, %RSD 0.01 and 3.16 (n = 5) for potential and intensity, respectively. Finally, the proposed electrochemical sensor was successfully applied to the determination of oleuropein in an olive leaf extract prepared by ultrasound‐assisted extraction. The results obtained with the proposed electrochemical sensor were compared with Capillary Zone Electrophoresis analysis with satisfactory results.

A Greener Approach to Prepare Natural Deep Eutectic Solvents

“…In previous works, it has been demonstrated that NADES are enhancers for electrochemical detection of phenolic compound ,. This effect is due to the interaction of the analyte with the supramolecular structure of NADES, providing a suitable environment for electron transference.…”

“…This effect is due to the interaction of the analyte with the supramolecular structure of NADES, providing a suitable environment for electron transference. In order to challenge MW‐NADES, electrochemical measurements were performed at room temperature, following the conditions previously reported by Gomez et al . with some modifications.…”

“…Three different microwave (MW) NADES were prepared and compared with those obtained by the most common HS method and comparable chemical and physical behavior were observed. Indeed, two known analytical applications for NADES were tested:, a) extraction media for phenolics and alkaloids from plant, b) enhancers for electrochemical detection of phenolic compounds. Analytical parameters were compared with those obtained with traditional solvents and conventionally prepared NADES with highly promising results.…”

Soft Electronics Based on Liquid Conductors

“…Another liquid conductor that also offers great promise for soft electronics is deep eutectic solvents. [70][71][72][73][74] Since Abbott et al presented the first deep eutectic solvent example as a product of mixing choline chloride with urea, [75] it has aroused great Figure 7. a) A thermal diffusion model to explain the thermoelectric conversion.…”

“…Another liquid conductor that also offers great promise for soft electronics is deep eutectic solvents. [ 70–74 ] Since Abbott et al. presented the first deep eutectic solvent example as a product of mixing choline chloride with urea, [ 75 ] it has aroused great interests in green synthesis owing to their unique physicochemical properties like low volatility, electrochemical stability, and high ionic conductivity.…”