Trace Determination of Acesulfame-K Using Voltammetric Nanosensor and Evaluation of Kinetic Parameters
Authors: Hajimosaei Samaneh , Islamnezhad Akbar 
Published: February 2020

Because of widespread application in food industry, measurement of Acesulfame-K (AcK) is an important subject. This material is a synthetic and non-caloric sweetener that has been widely used instead of sugar in foodstuffs. Powerful analytical methods are needed for this growing market to assure quality control and the ingredients of the products. Till now, several analytical methods have been reported concerning the determination of AcK and other sweeteners including linear sweep voltammetry, solid-phase extraction and liquid chromatography–tandem mass spectrometry, liquid extraction and liquid chromatography-tandem mass spectrometry, square-wave voltammetry, differential pulse voltammetry, capillary electrophoresis, FT-Raman spectroscopy, Spectrophotometry, sinusoidal envelope voltammetry and potentiometry [1-5]. Consequently, the determination of AcK is regarded as an interesting issue for many researchers that work in the spectroscopic, chromatographic and electroanalytical methods of analytical chemistry.
Electroanalytical literature survey shows not only the lack of mechanistic and kinetic information about AcK electrochemical behavior, but also absence of ultrasensitive AcK nanosensor. Thus, construction of nanoparticle-based AcK voltammetric sensor and evaluation of kinetic parameters of AcK can be considered as the novel aspects of this research that might differentiate this one from the previously reported ones, to the best of our knowledge.
The cyclic voltammetric (CV), differential pulse voltammetric (DPV) and electrochemical impedance spectroscopic (EIS) measurements were performed with µAutolab FRA2 Potentiostat-Galvanostat. A three-electrode system was used with the Pt rod (2 mm/ 87 mm) or NPtAPE as working electrodes, glassy carbon electrode (GC rod 2mm/ 76mm) as the counter and an Ag/AgCl as the reference electrode (Autolab comp.). All tests were conducted under room temperature. A digital pH meter (Jenway 370) was applied for pH adjustment.
The AcK voltammetric nanosensor (NPtAPE) was constructed by using nano Platinum (NPt) and Agar paste (AP) as electrocatalyst and inert support material, respectively. The NPt content of NPtAPE is an important factor that affects the obtained current intensity of this nanosensor. Using Nyquist manner plots, the EIS confirmed diminishing of charge transfer resistance (Rct) and enhancing electron transfer at the surface of NPtAPE. Various supporting electrolytes such as KCl, NaNO3 and KNO3 were tested to select the best of them in forthcoming experiments. Exact experimental calculations revealed the best pH and kinetic parameters of electrooxidation of AcK at the working electrode surface. After that, probable mechanism for this process was suggested which has three steps. NPtAPE showed linear dynamic ranges and extraordinary pM detection limit that made it a powerful device in sensing of AcK at trace level. In the final step of the work, NPtAPE was utilized for AcK quantitation in candy samples purchased from different companies successfully.
In summary, NPtAPE is a new voltammetric nanosensor for ultrasensitive and rapid AcK determination in candy samples. Hence, it can be recommended for the routine quality control of AcK in food products. The proposed method was based on the oxidation of AcK by appropriate potential at the NPtAPE surface. The principal advantages of the proposed nanosensor are its excellent detection limit, wide linear dynamic ranges, simplicity, selectivity and rapidity. The heterogeneous rate constant confirms the catalytic role of NPt particles in enhancing S/N ratio in order to constructing ultrasensitive nanosensor.

Keywords:
Acesulfame-K; Nano Platinum; Cyclic voltammetry; Differential pulse voltammetry; Kinetic parameters

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