According to the type of real sample (apple juices for babies) in which the analyte is determined, the systems described in this work can be very promising tools for quality control purposes in food industry. It is noteworthy that this is the second time that exclusively electrochemical methods have been used to determine AA in commercial baby juices [9].Finally, these devices were also structurally characterized by means of Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectroscopy (EDS). AuSNPs and AuSNPs/CeO2 nanocomposite were characterized by UV-vis spectroscopy, X-Ray Diffraction (XRD) and Transmission Electron Microscopy (TEM;.2.?Experimental Section2.1. Reagents and MaterialsMethyltrimethoxysilane (MTMOS) was from Merck (Darmstad, Germany) and HCl was from Panreac (Barcelona, Spain).
KH2PO4 and K2HPO4 for phosphate buffer solution (PBS) and potassium hexacyanoferrate(II) were from Fluka (Buchs, Switzerland). Sodium citrate trihydrate was purchased from Scharlau (Scharlab, Barcelona, Spain) and potassium tetrachloroaurate(III), ascorbic acid and nanopowder cerium(IV) oxide (99.95%) form from Sigma-Aldrich (Sigma, Steinheim, Germany). Graphite powder natural, high purity-200 Mesh, 99.9999% (metal basis), was from Alfa-Aesar (Johnson Matthey GmbH, Germany). All reagents were of analytical grade and used as received without further purification. Nanopure water was obtained by passing twice-distilled water through a Milli-Q system (18 M??cm, Millipore, Bedford, MA, USA). Glass capillary tubes, i.d. 1.15 mm (A = 0.0415 cm2), were used as the bodies of the composite electrodes.
The nitrogen used for getting inert atmospheres and deaerating solutions in the measuring cell was N-55 type.2.2. InstrumentationThe synthesis of the SNGC material was carried out by sonicating with a high power SONICATOR 3000 ultrasonic generator from MISONIX Inc. (Farmingdale, NY, USA) equipped with a 13-mm titanium tip, that provides a maximum output power of 600 W.The voltammetric measurements were made on an Autolab? PGSTAT20 (Ecochemie, Utrecht, The Netherlands) potentiostat/galvanostat connected to a personal computer and a 663 Metrohm VA Stand module, using the software GPES (General Purpose Electrochemical System) 4.9 ver. for waveform generation, data acquisition and elaboration. The experiments were carried out in a single-compartment three-electrode cell, at room temperature (25 �� 1 ��C).
The counter electrode was a platinum wire, and a silver/silver chloride/3M KCl electrode was used as the reference. The composite-filled glass capillary tubes were used as the working electrode.UV-Visible measurements were made with the Batimastat Jasco 32 software using a Jasco V-550 (Easton, MD, USA) UV-visible spectrophotometer connected to a personal computer.