A Novel Multicommuted Flow Method with Nanocolloidal Manganese(IV)-Based Chemiluminescence Detection for the Determination of the Total Polyphenol Index

Integrated instrumental setup comprising an automatic solution handling module and homemade luminometer with two photodetectors for the determination of antioxidants in wines

This study describes the development of an integrated instrumental setup, comprising a multi-commuted flow analysis module for solution handling and a homemade luminometer assembled with two photodetectors for luminescence detection. This setup controlled by an Arduino Due board was used to develop an analytical procedure for determining antioxidants in red and white wines, using chemiluminescence detection. The analytical procedure is based on the reaction of hypochlorite with antioxidants present in wine, followed of oxidizing reaction with luminol in an alkaline medium (pH > 9). After determining the optimal operational parameters, the following analytical parameters were obtained: linear responses for gallic acid concentrations ranging from 0.75 to 4.0 g L-1 (r2 = 0.999) for red wine and from 75 to 500 mg L-1 (r2 = 0.994) for white wine, a coefficient of variation of 2.71% (n = 9) for a wine sample with an antioxidant concentration of 1.57 g L-1 in gallic acid equivalent, recoveries ranging from 85 to 114%, an analytical throughput of 100 determinations per hour, consumption of 0.35 μg of hypochlorite and 53 mg of luminol per determination, and limits of detection of 0.25 g L-1 and 29 mg L-1 for red and white wine, respectively.

A novel electrochemical micro-titration method for quantitative evaluation of the DPPH free radical scavenging capacity of caffeic acid

In this report, the stoichiometric ratio (R) for the interaction of diphenylpicrylhydrazyl (DPPH) radicals with the antioxidant was employed as an evaluation index for the DPPH radical scavenging activity of antioxidants. This evaluation index was related only to the stoichiometric relationship of DPPH radicals with the antioxidant and had no relationship with the initial DPPH amount and the sample volume, which could offer a solution to the problem of poor comparability of EC50 values under different conditions. A novel electrochemical micro-titration method was proposed for the determination of the stoichiometric ratio (R) for the interaction of DPPH radicals with the antioxidant. This electrochemical micro-titration model was verified using caffeic acid as the DPPH radical scavenger, with the stoichiometric ratio (R) of DPPH radicals to caffeic acid determined to be in the range of 2.003–2.046. The calculated EC50 values were 0.513, 1.011, and 1.981 × 10–5 mol/L for 2.10, 4.05, and 8.02 × 10–7 moL of added DPPH radicals, respectively. The proposed method showed no differences from the conventional method, but had better precision and reliability, and used a smaller amount of sample.

Optical Devices Constructed From Responsive Microgels for Polyphenols Detection

Polyphenols are used as antioxidants in various foods and beverages, which are considered to be a health benefit. The measurement of polyphenols contents is of great interest in food chemistry and health science. This work reported a microgels based photonic device (etalon) to detect polyphenols. Dopamine was used as a model compound of polyphenols. Herein, we proposed a “block” concept for dopamine detection. The dopamine was oxidized and formed dopamine films catalyzed by tyrosinase on the surface of etalon. As the etalon was immersed in ZnCl₂, the dopamine films blocked the ZnCl₂ diffusion into etalon that caused optical property changes. The film thickness is associated with the concentration of dopamine which can be readout via optical signals.

Flow-based System: A Highly Efficient Tool Speeds Up Data Production and Improves Analytical Performance

In this review, we cite references from the period between 2015 and 2020 related to the use of a flow-based system as a tool to obtain a modern analytical system for speeding up data production and improving performance. Based on a great deal of concepts for automatic systems, there are several research groups introduced in the development of flow-based systems to increase sample throughput while retaining the reproducibility and repeatability as well as to propose new platforms of flow-based systems, such as microfluidic chip and paper-based devices. Additionally, to apply a developed system for on-site analysis is one of the key features for development. We believe that this review will be very interested and useful for readers because of its impact on developing novel analytical systems. The content of the review is categorized following their applications including quality control and food safety, clinical diagnostics, environmental monitoring and miscellaneous.

Flow analysis with chemiluminescence detection: Recent advances and applications

This article highlights the most important developments in flow analysis with chemiluminescence (CL) detection, describing different flow systems that are compatible with CL detection, detector designs, commonly applied CL reactions and approaches to sample treatment. Recent applications of flow analysis with CL detection (focusing on outputs published since 2010) are also presented. Applications are classified by sample matrix, covering foods and beverages, environmental matrices, pharmaceuticals and biological fluids. Comprehensive tables are provided for each area, listing the specific sample matrix, CL reaction used, linear range, limit of detection and sample treatment for each analyte. Finally, recent and emerging trends in the field are also discussed.

Application of direct-injection detector integrated with the multi-pumping flow system to chemiluminescence determination of the total polyphenol index

In this work, we present a novel chemiluminescence (CL) method based on direct-injection detector (DID) integrated with the multi-pumping flow system (MPFS) to chemiluminescence determination of the total polyphenol index. In this flow system, the sample and the reagents are injected directly into the cone-shaped detection cell placed in front of the photomultiplier window. Such construction of the detection chamber allows for fast measurement of the CL signal in stopped-flow conditions immediately after mixing the reagents. The proposed DID-CL-MPFS method is based on the chemiluminescence of nanocolloidal manganese(IV)-hexametaphosphate-ethanol system. The application of ethanol as a sensitizer, eliminated the use of carcinogenic formaldehyde. Under the optimized experimental conditions, the chemiluminescence intensities are proportional to the concentration of gallic acid in the range from 5 to 350 ng mL(-1). The DID-CL-MPFS method offers a number of advantages, including low limit of detection (0.80 ng mL(-1)), high precision (RSD = 3.3%) and high sample throughput (144 samples h(-1)) as well as low consumption of reagents, energy and low waste generation. The proposed method has been successfully applied to determine the total polyphenol index (expressed as gallic acid equivalent) in a variety of plant-derived food samples (wine, tea, coffee, fruit and vegetable juices, herbs, spices).