Biomass derived worm-like nitrogen-doped-carbon framework for trace determination of toxic heavy metal lead (II)

Nitrogen functionalized biomass derived mesoporous carbon nanomaterials for electrochemical detection of lead (II) ions

This study has explored the sustainable solution after designing an economical metal-free biomass-derived nanocarbon for the selective sensing of lead. The nitrogen and sulfur-rich mesoporous nanocarbon is designed through a facile hydrothermal-assisted thermal annealing method. The high-temperature treatment gave nanocarbon unique carbon dot decorated layered morphology, while nitrogen and sulfur precursor thiourea and melamine strengthened the nanomaterial stability, sensitivity, and selectivity toward lead metal ions. The high specific surface area of mesoporous nanocarbon viz., 1671.93 m2/g with the pore width and pore volume of 2.02 nm and 0.476 cm3/g has enhanced the conductivity of as-synthesized sensor, which helps in increasing sensitivity toward lead. The high conductivity was also confirmed through cyclic voltammetry, where an 80 % increment in current was observed in the case of the modified electrode when compared with bare GCE. The differential pulse normal voltammetry and differential pulse anodic stripping voltammetry were performed to calculate the detection limit, where an excellent detection limit of 22 nM was obtained from the DPASV technique. Moreover, the nanomaterial was also tested for detecting lead in tap water. The as-synthesized nanocomposite is highly efficient and selective for the detection of lead. This study will motivate the researchers to engineer sustainable and efficient devices for sensing metal pollutants.

Recent advances in the modification of electrodes for trace metal analysis: a review

This review paper summarizes the research published in the last five years on using different compounds and/or materials as modifiers for electrodes employed in trace heavy metal analysis. The main groups of modifiers are identified, and their single or combined application on the surface of the electrodes is discussed. Nanomaterials, film-forming substances, and polymers are among the most used compounds employed mainly in the modification of glassy carbon, screen-printed, and carbon paste electrodes. Composites composed of several compounds and/or materials have also found growing interest in the development of modified electrodes. Environmentally friendly substances and natural products (mainly biopolymers and plant extracts) have continued to be included in the modification of electrodes for trace heavy metal analysis. The main analytical performance parameters of the modified electrodes as well as possible interferences affecting the determination of the target analytes, are discussed. Finally, a critical evaluation of the main findings from these studies and an outlook discussing possible improvements in this area of research are presented.

Cd2+ Detection by an Electrochemical Electrode Based on MWCNT-Orange Peel Activated Carbon

This study reports the development of a new electrochemical sensor based on a carbon paste electrode (CPE) composed of biomass-based orange peel activated carbon (ACOP) and multiwalled carbon nanotubes (MWCNTs), and this composite is used for the electrochemical detection of cadmium ions (Cd2+). The ACOP/MWCNT composite was characterized by FTIR, Raman, and electrochemical impedance spectroscopy. The electrochemical evaluation of Cd2+ was performed using square wave and cyclic voltammetry. The ACOP/MWCNT-CPE electrochemical sensor exhibited a coefficient of determination r2 of 0.9907, a limit of detection of 0.91 ± 0.79 μmol L-1, and a limit of quantification of 3.00 ± 2.60 μmol L-1. In addition, the developed sensor can selectively detect Cd2+ in the presence of different interferents such as Zn2+, Pb2+, Ni2+, Co2+, Cu2+, and Fe2+ with a relative standard deviation (RSD) close to 100%, carried out in triplicate experiments. The ACOP/MWCNT-CPE presented high sensitivity, stability, and reproducibility and was successfully applied for the detection of Cd2+ in river water samples with recovery rate values ranging from 97.33 to 115.6%, demonstrating to be a very promising analytical alternative for the determination of cadmium ions in this matrix.

Nanostructured N, S, and P-Doped Elaeagnus Angustifolia Gum-Derived Porous Carbon with Electrodeposited Silver for Enhanced Electrochemical Sensing of Acetaminophen

Acetaminophen (N-acetyl-p-aminophenol, APAP) is regularly used for antipyretic and analgesic purposes. Overdose or long-term exposure to APAP could lead to liver damage and hepatotoxicity. In this study, the approach of enhanced electrochemical detection of APAP by nanostructured biomass carbon/silver was developed. Porous biomass carbon derived from Elaeagnus Angustifolia gum was prepared by pyrolysis with co-doping of electron-rich elements of nitrogen, sulfur, and phosphorus. The electrodeposition of silver onto a glassy carbon electrode modified with porous carbon could enhance the sensing signal towards APAP. Two linear ranges from 61 nM to 500 μM were achieved with a limit of detection of 33 nM. The developed GCE sensor has good anti-interference, stability, reproducibility, and human urine sample analysis performance. The silver-enhanced biomass carbon GCE sensor extends the application of biomass carbon, and its facile preparation approach could be used in constructing disposable sensing chips in the future.

An Electroanalytical Solution for the Determination of Pb2+ in Progressive Hair Dyes Using the Cork-Graphite Sensor

Lead is one of the most toxic metals for living organisms: once absorbed by soft tissues, it is capable of triggering various pathologies, subsequently bioaccumulating in the bones. In consideration of this, its detection and quantification in products for human consumption and use is of great interest, especially if the procedure can be carried out in an easy, reproducible and economical way. This work presents the results of the electroanalytical determination of lead in three different commercial products used as progressive hair dyes. Analyses were performed by cyclic voltammetry (CV) and differential pulse stripping voltammetry (DPSV) using a composite cork–graphite sensor in 0.5M H₂SO₄ solution or 0.1M acetate buffer (pH 4.5), in the presence and absence of hair dye samples. The H₂SO₄ solution gave better results in terms of analyte sensitivity than the acetate buffer electrolyte. In both cases, well-defined signals for lead were obtained by DPSV analyses, enabling the calibration curve and figures of merit to be determined. The limits of detection (LOD) were found to be approximately 1.06 µM and 1.26 µM in H₂SO₄ and acetate buffer, respectively. The DPSV standard addition method was successfully applied to quantify the lead in hair dye samples, yielding values below 0.45% in Pb. All three analyzed samples were shown to comply with the limit set by the Brazilian Health Regulatory Agency, i.e., 0.6% lead in this type of product. The comparison of the electroanalytical results with those obtained by the reference method, based on the use of inductively coupled plasma optical emission spectrometry (ICP–OES), confirmed that the electroanalytical detection approach is potentially applicable as a strategy for quality control.

Nano-ZnS decorated hierarchically porous carbon electrocatalyst with multiple enzyme-like activities as a nanozyme sensing platform for simultaneous detection of dopamine, uric acid, guanine, and adenine

The simultaneous detection of multiple biological small molecules is critical for human health evaluation and disease prevention. In this study, a nano-ZnS decorated hierarchically porous carbon (ZSHPC) electrocatalyst with multiple enzyme-like activities as a nanozyme sensing platform for simultaneous derivative voltametric detection of four important biological small molecules, dopamine (DA), uric acid (UA), guanine (G), and adenine (A), is successfully synthesized via an in situ hydrothermal reaction using leaves of Cinnamomum camphora (L.) after the extraction of essential oil as a carbon source, ZnCl₂ as both zinc source and an activator, sulfuric acid as a sulfur source, and silica gel as a hard template. Activator together with the introduction of silica gel is beneficial for tuning pore structure. The in situ synthesized ZnS nanoparticles and sulfur doping improve the conductivity and cycling stability of the material. The ZSHPC electrode with multiple enzyme-like activities and oxidase-like characteristics was employed for the simultaneous detection of multiple target molecules in linear ranges of 0.3-500 μM with detection limits of 0.12 μM for DA, 0.26 μM for UA, 0.07 μM for G, and 0.075 μM for A. A derivative technique was selected for enhancing the peak resolution of the partial overlapped voltammograms and eliminating human error. Both the coefficient of determination and residual prediction deviation were used to evaluate this technique.

Fabrication of a Greener TiO2@Gum Arabic-Carbon Paste Electrode for the Electrochemical Detection of Pb2+ Ions in Plastic Toys

A novel greener methodology is reported for the synthesis of titanium dioxide (TiO2) nanoparticles (NPs) using gum Arabic (Acacia senegal) and the characterization of the ensuing TiO2 NPs by various techniques such as X-ray diffraction (XRD), Fourier transform infrared, Raman spectroscopy, scanning electron microscopy-energy dispersive X-ray, transmission electron microscopy (TEM), high resolution-TEM, and UV-visible spectroscopy. The XRD analysis confirmed the formation of TiO2 NPs in the anatase phase with high crystal purity, while TEM confirmed the size to be 8.9 ± 1.5 nm with a spherical morphology. The electrode for the electrochemical detection of Pb2+ ions was modified by a carbon paste fabricated using the synthesized TiO2 NPs. Compared to the bare electrode, the fabricated electrode exhibited improved electro-catalytic activity toward the reduction of Pb2+ ions. The detection limit, quantification limit, and the sensitivity of the developed electrode were observed by using differential pulse voltammetry to be 506 ppb, 1.68 ppm, and 0.52 ± 0.01 μA μM-1, respectively. The constructed electrode was tested for the detection of lead content in plastic toys.

The Use of Factorial Design and Simplex Optimization to Improve Analytical Performance of In Situ Film Electrodes

This work presents a systematic approach to determining the significance of the individual factors affecting the analytical performance of in-situ film electrode (FE) for the determination of Zn(II), Cd(II), and Pb(II). Analytical parameters were considered simultaneously, where the lowest limit of quantification, the widest linear concentration range, and the highest sensitivity, accuracy, and precision of the method evidenced a better analytical method. Significance was evaluated by means of a fractional factorial (experimental) design using five factors, i.e., the mass concentrations of Bi(III), Sn(II), and Sb(III), to design the in situ FE, the accumulation potential, and the accumulation time. Next, a simplex optimization procedure was employed to determine the optimum conditions for these factors. Such optimization of the in situ FE showed significant improvement in analytical performance compared to the in situ FEs in the initial experiments and compared to pure in situ FEs (bismuth-film, tin-film, and antimony-film electrodes). Moreover, using the optimized in situ FE electrode, a possible interference effect was checked for different species and the applicability of the electrode was demonstrated for a real tap water sample.