Electrochemical platform based on molecularly imprinted polymer with zinc oxide nanoparticles and multiwalled carbon nanotubes modified screen-printed carbon electrode for amaranth determination.

A novel electrochemical platform for amaranth determination has been developed using a rapid, easy, inexpensive, and portable molecularly imprinted polymer technique. The MIP platform was fabricated by electropolymerizing melamine as monomer in the presence of amaranth as template on the surface of ZnO-MWCNT/SPCE. Then, amaranth was completely eluted, leaving imprinted cavities in the polymeric film that could effectively recognize amaranth in solution. The electrochemical platform based on a molecularly imprinted polymelamine was analyzed by scanning electron microscopy (SEM), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and differential pulse voltammetry (DPV). Under optimum conditions, the developed MIP/ZnO-MWCNT/SPCE platform can be properly used for amaranth determination, with high sensitivity of 96.2 µA µM cm-2, two linear concentration ranges (0.01 to 1 µM and 1 to 1000 µM) and a low limit of detection of 0.003 µM. The anodic peak potential of amaranth was found to be 0.73 V. Additionally, the polymelamine MIP films specifically recognize amaranth molecules, making it possible to detect amaranth in a complex solution with high selectivity, excellent repeatability, reproducibility, and stability. The MIP/ZnO-MWCNT modified screen-printed carbon electrode was successfully applied to determine amaranth in pharmaceutical and water samples, with recovery values ranging from 99.7 to 102% and RSD% values less than 3.2%.

Nanographene-based electrochemical sensors for ultrasensitive determination of sorbic acid from food.

Ultrasensitive determination of sorbic acid in food is essential for the assessment of the food quality. Therefore, two sensors based on nanographene decorated with gold nanoparticle paste modified with metal porphyrins (Zn protoporphyrin IX, and 2,3,7,8,12,13,17,18 octaethyl, 21H, 23H-porphirine Mn(III) chloride) were proposed for the determination of sorbic acid in food (bakery products and mayonnaise). Square-wave voltammetry was used for the characterization and validation of the proposed sensors. Response characteristics showed that the limits of detection for both sensors were 0.33 µmol L-1 while the limits of quantification were 1.00 µmol L-1. Both sensors can be used for the determination of sorbic acid in the concentration range 1-1000 µmol L-1, the linear concentration range making them appropriate for the assay of sorbic acid in food. The highest sensitivity (0.35 nA/µmol L-1) was recorded when the sensor based on 2,3,7,8,12,13,17,18 octaethyl, 21H, 23H-porphirine Mn(III) chloride was used, proving the higher electrocatalytic effect of this electrocatalyst versus the one of the Zn protoporphyrin IX. High recoveries (values higher than 95.00%) and low RSD (%) values (lower than 5.00%) were recorded for both sensors when used for the determination of sorbic acid in bread and mayonnaise, proving the high reliability of the proposed sensors and method.

Sulfur-Doped Graphene-Based Electrochemical Sensors for Fast and Sensitive Determination of (R)-(+)-Limonene from Beverages.

Two sensors based on sulfur-doped graphene, a gold nanoparticle paste modified with 5,10,15,20-tetraphenyl-21H,23H-porphine and 5,10,15,20-tetrakis (pentafluorophenyl chloride)-21H,23H-iron (III) porphyrin, were proposed for the determination of R-limonene in beverages (triple sec liqueur and limoncello). Differential pulse voltammetry was the method used to characterize and validate the proposed sensors. The response characteristics showed that the detection limits for both sensors were 3 × 10-6 mol L-1, while the quantification limits were 1 × 10-5 mol L-1. Both sensors can be used to determine R-limonene in a concentration range between 1 × 10-5-6 × 10-4 mol L-1 for TPP/AuNPs-S-Gr and 1 × 10-5-1 × 10-3 mol L-1 for Fe(TPFPP)Cl/AuNPs-S-Gr. The highest sensitivity (0.7068 µA/mol L-1) was recorded when the TPP/AuNPs-S-Gr sensor was used, proving that the electrocatalytic effect of this electrocatalyst is higher compared to that of Fe(TPFPP)Cl/AuNPs-S-Gr. High recoveries (values greater than 99.00%) and low RSD values (%) (below 5.00%) were recorded for both sensors when used to determine R-limonene in triple sec liqueur and limoncello.