Sensitive Voltammetric Sensor for Amaranth Based on Ordered Mesoporous Carbon

Continuous successive cycles of biosorption and desorption of acid red 27 dye using water hyacinth leaves as an effective, economic, and ecofriendly biosorbent

We investigated the capacity of water hyacinth leaves (LEC) to biosorb 75 mg/L acid red 27 (AR27) in a continuous system comprising 30 successive biosorption/desorption cycles in a packed-bed column at pH 2.0 and 56.5 L/m²·h volumetric flux. Using 0.025 M NaHCO₃ eluent at 113 L/m²·h volumetric flux, all the dye was desorbed (100% desorption efficiency) from the loaded LEC biomass within 5-6 h. The same biosorbent was used for 147.5 consecutive days. The AR27 biosorption capacity, breakthrough time, and exhaustion time decreased from 69.4 to 34.5 mg/g, 74.81 to 14.1 h, and 101.1 to 34.1 h, respectively, and the critical bed height increased from 1.04 to 2.35 cm, as the number of biosorption/desorption cycles increased from 1 to 30. LEC life factor based on biosorption capacity predicted that the packed bed would be exhausted after 51.95 cycles. LEC is a promising biosorbent for bioremediation of AR27-laden wastewaters.

A novel voltammetric amaranth sensor based on screen printed electrode modified with polypyrrole nanotubes

Azo dyes are the most used type of dye in the textile industry. Some of these dyes have the potential to be extremely toxic to both human health and the environment. The purpose of this study was to develope an electrochemical sensor for detection of amaranth. The electrochemical sensor based on the modification of a screen-printed electrode via polypyrrole nanotubes (PPy NTs/SPE) for detection of amaranth was developed. The preparation of PPy NTs was performed through the pyrrole monomer oxidation with iron (III) chloride in exposure to methyl orange as structure-guiding agent. Findings exhibited an excellent electrocatalytic activity of as-fabricated sensor for amaranth detection. Our sensor under the optimized circumstances also had a broad linear dynamic range (between 0.03 μM and 290.0 μM) and a narrow limit of detection (0.01 μM) towards the amaranth detection. Moreover, the proposed sensor could practically and successfully determine the amaranth content present in the real food specimens, with acceptable recovery rates.

Glassy Carbon Electrode Modified with N-Doped Reduced Graphene Oxide Sheets as an Effective Electrochemical Sensor for Amaranth Detection

Amaranth is one of the synthetic azo colorants used to improve the appearance and to increase the appeal of some foods and soft drinks. The excessive consumption of amaranth can be associated with health side effects, emphasizing the need to monitor this food dye. Accordingly, the present study aimed to introduce an electrochemical sensor of glassy carbon electrode (GCE) modified with N-doped reduced graphene oxide (N-rGO), N-rGO/GCE, to detect the amaranth sensitively and rapidly. Several electrochemical techniques such as differential pulse voltammetry (DPV), linear sweep voltammetry (LSV), chronoamperometry (CHA), and cyclic voltammetry (CV) are exploited for the evaluation of the efficiency of the developed electrode for the detection of amaranth. We found that N-rGO/GCE enhanced amaranth oxidation, thus significantly elevating the current signal. Amaranth showed that calibration curves ranged from 0.1 to 600.0 µM, and the limit of detection (LOD) (S/N = 3) was 0.03 μM. Finally, the developed sensor was effectively applied for real samples (tap water, apple juice, and orange juice) with acceptable recovery values from 96.0 to 104.3%.

Recent advantages in electrochemical monitoring for the analysis of amaranth and carminic acid food colors

This study provides a comprehensive review of the latest developments in the electrochemical impressions of the important dyestuffs including amaranth and carminic acid. Food colors are organic substances that have important effects on human health and food safety. While these substances do not pose a problem when used in the daily intake (ADI) amounts, they harm human health when consumed excessively. Amaranth and carminic acid are synthetic and natural food colors ingredients, respectively. Analysis of these substances in food, pharmaceutical, cosmetic and textile samples is extremely important because of their genotoxicity, cytostatic and cytotoxic effects. Electroanalytical methods, which have great advantages over traditional analytical methods, shed light on the scientific world. Electrochemical monitoring modules, which are fast, simple, accurate, reliable, and highly selective, are promising for the determination of both substances. Until now, amaranth and carminic acid food determinations have been carried out successfully with electrochemical monitoring techniques in many numbers in the literature. Voltammetric techniques are the most widely used among these electroanalytical methods. In particular, square wave and differential pulse voltammetric techniques, which have extraordinary properties, have been heavily preferred. Limits of detection (LOD) comparable to the standard analytical method have been achieved using these methods, which have very quick analysis durations, high precision and accuracy, do not require long preprocessing, and have great selectivity. In addition, more sensitive and selective analyses of amaranth and carminic acid in natural samples were carried out with numerous indicator electrodes. The merits of powerful electrochemical monitoring studies for the determination of both food colors during the last decade are presented in this study. Moreover, parameters such as analytical applications, detection limits, electrochemical methods, selectivity, working electrodes, and working ranges are summarized in detail.

Continuous biosorption of acid red 27 azo dye by Eichhornia crassipes leaves in a packed-bed column

In this work, the biosorption behavior of acid red 27 (AR27) dye using Eichhornia crassipes leaves (LECs) in a packed-bed column was investigated by varying relevant operational parameters and assessment of mathematical models. Results showed that the zero-charge point of LECs was 2.37 and that optima pH and volumetric flux of the influent solution for AR27 biosorption were 2.0 and \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$56.5\ \hbox {L}/\hbox {m}^{2}\cdot \hbox {h}$$\end{document}56.5L/m2·h, respectively. The maximum specific and volumetric biosorption capacities were observed at influent AR27 concentrations and with LEC bed heights ranging between 50 and 400 mg/L and 2 and 8 cm, respectively. It was also found that if LEC bed height was increased and volumetric flux and AR27 concentration of the influent solution decreased, service and saturation time increased. Modeling results revealed that the Thomas, bed depth service time, Yoon–Nelson, dose-response, and logistic models accurately described the dynamic performance of the packed-bed column in terms of pH, AR27 concentration, and volumetric flux of influent AR27 solution, as well as that of LEC bed height. The findings revealed that LECs exhibited remarkable potential for the biosorption of AR27 from aqueous solutions in a packed-bed column and could potentially be useful for the treatment of AR27-laden wastewater.

A new voltammetric sensor based on poly(L-cysteine)/GR composite film modified electrode for the sensitive determination of amaranth in wastewater

A simple voltammetric sensor was first constructed by dripping graphene (GR) on to the glass carbon electrode (GCE) and subsequently electro-polymerizing L-cysteine film. The sensor had a good voltammetric response to amaranth and linear in the range of 1.0 × 10^-8-1.0 × 10^-6 mol L^-1. The detection limit of amaranth was 4.0 × 10^-9 mol L^-1 (S/N = 3). Using this method, we successfully obtained satisfactory results of amaranth in confectionery wastewater. This work promoted the potential applications of amino acid materials and GR in environmental pollution science.

Highly selective and sensitive detection of amaranth by using carbon dots-based nanosensor

In this work, a novel fluorescence nanosensor for selective and sensitive determination of amaranth was constructed using carbon dots (C-dots). Water soluble C-dots with strong fluorescence were obtained by a simple microwave-assisted method using urea and glycine as raw materials. It was found that amaranth can efficiently and sensitively quench the C-dots fluorescence by the inner filter effect (IFE) and non-radiative energy transfer (NRET) mechanisms. The fluorescence quenching efficiency (F₀/F) was strongly correlated with the concentration of amaranth in the 0.2–30 μM range. The detection limit (LOD) is 0.021 μM. There was no significant change in the fluorescence intensity of C-dots when other potentially interfering substances were present in the system. Our C-dots-based nanosensor was successfully utilized for the analysis of amaranth in drinks and showed rapid, sensitive and accurate responses. It indicates that the novel C-dots-based nanosensor has great potential in amaranth detection for real-life applications.

Illustration of the synthesis of C-dots and the determination of amaranth based on the fluorescence quenching of C-dots.