Sensitive and selective determination of vitamin B2 in non-alcoholic beverage and milk samples at poly (glutamic acid)/zinc oxide nanoparticles modified carbon paste electrode

Background

The deficiency of vitamin B2 can lead to many health problems. Therefore, it is necessary to develop a sensitive, selective and fast method for the determination of vitamin B2 in food samples. In this work, a sensitive, selective and low-cost electrochemical sensor was developed using poly (glutamic acid) and Zinc oxide nanoparticles (ZnO NPs) for vitamin B2 in non-alcoholic beverage and milk samples.

Methods

The modification of the electrode surface was carried out by electropolymerization of glutamic acid on ZnO NPs–carbon paste electrode (ZnO NPS–CPE). The prepared electrodes were characterized by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM) and X-Ray diffraction (XRD). CV and square wave voltammetry (SWV) were used to investigate the electrochemical behavior of vitamin B2 at the modified electrode. The effect of various parameters such as amount of ZnO NPs, polymerization cycle, concentration of the monomer, pH, scan rate and accumulation time were optimized to obtain maximum sensitivity at the modified electrode.

Results

The developed sensor showed high electrocatalytic activity towards vitamin B2. Under the optimized conditions, the developed sensor showed a linear response in the range 0.005–10 µM with a low detection limit of (LOD) 0.0007 ± 0.00001 µM and high sensitivity of 21.53 µA/µM.

Conclusions

A reproducible, repeatable, stable and selective sensor was successfully applied for the quantification of vitamin B2 in beverage and milk samples with acceptable recoveries in the range of 88–101%.

Enhanced Electrochemical Determination Of Riboflavin In Biological And Pharmaceutical Samples At Poly (Arginine) Modified Carbon Paste Electrode

An electrogenerated Polyarginine modified carbon paste electrode (PAMCPE) was fabricated through a simple electropolymerization procedure. The devised electrode was characterized by cyclic voltammetry (CV) and Field Emission Scanning Electron Microscopy (FESEM). This electrode was utilized for electrocatalytic estimation of Riboflavin (RF) and its instantaneous resolution with ascorbic acid (AA) and folic acid (FA) in phosphate buffer solution (PBS) of pH 6.0 by differential pulse voltammetry (DPV). It was observed to be a very responsive electrode for the electrochemical detection and quantification of RF. It was revealed that PAMCPE generates higher current response towards RF contrast to the bare carbon paste electrode (BCPE). Under optimized condition, the RF oxidation current values were linearly reliant on the RF concentration increment with a limit of detection (LOD) of 9.3·10-8 M using DPV. The stable PAMCPE was effectively applied for estimation of RF in B-complex pill and complex human blood serum samples.

Sensor systems for bacterial reactors: A new flavin-phenol composite film for the in situ voltammetric measurement of pH

Monitoring pH within microbial reactors has become an important requirement across a host of applications ranging from the production of functional foods (probiotics) to biofuel cell systems. An inexpensive and scalable composite sensor capable of monitoring the pH within the demanding environments posed by microbial reactors has been developed. A custom designed flavin derivative bearing an electropolymerisable phenol monomer was used to create a redox film sensitive to pH but free from the interferences that can impede conventional pH systems. The film was integrated within a composite carbon-fibre-polymer laminate and was shown to exhibit Nernstian behaviour (55 mV/pH) with minimal drift and robust enough to operate within batch reactors.

Surface functionality density regulated in situ reduction of nanosilver on hierarchial wrinkled mesoporous silica nanoparticles and their antibacterial activity

Hierarchical wrinkled mesoporous silica nanoparticles (WMS NPs) bedecked with diverse functionality density of amino groups (WMSs-N2, WMSs-NN and WMSs-NNN) were first synthesized via typical Sol–Gel method, and then utilized for the in situ reduction of nanosilver with sodium borohydride. Elegantly distributed Ag NPs (ca. 7–10 nm, 3–5 nm) on WMSs-N2 and WMSs-NN without any agglomeration were obtained respectively, while Ag NPs (ca. 50 nm) dispersed on WMSs-NNN were obviously larger and slightly agglomerated. Compared to pure Ag NPs, all the obtained Ag@WMSs composites were durable and displayed much better antibacterial performance, with a minimal inhibitory concentration of 12–80 mg L⁻¹ and a minimal bactericidal concentration of 24–108 mg L⁻¹, respectively. Moreover, it was found that the functionality density of amino groups and the specific surface area of WMSs played a crucial role for the antibacterial performance of the obtained nanocomposites. Because WMSs-NN had higher specific surface area and surface amino density than WMSs-N2, the size and dispersion of Ag NPs on WMSs-NN were smaller and superior to those of Ag NPs on WMSs-N2, respectively. Accordingly, Ag@WMSs-NN displayed a better antibacterial capacity than Ag@WMSs-N2. As for Ag@WMSs-NNN, owing to the high loading content of Ag NPs, they exhibited the best antibacterial and bactericidal properties.

Nanosilver with diverse particle size was attached onto hierarchical WMS, and the resulted samples showed excellent antibacterial properties.