Spectrophotometric and colorimetric determination of gallium (III) with p-aminohippuric acid-functionalized citrate capped gold nanoparticles

A new technique for sensing Ga(III) concentration based on polyvinyl alcohol-citrate capped gold nanoparticle-p-aminohippuric acid hybrid (or three-layer core-shell configurations) has been demonstrated. The p-aminohippuric acid capped citrate-gold nanoparticles were comfortably agglomerated in the presence of Ga(III), and the color of the reaction quickly turned from red to violet or blue. Under the detection conditions, a good linear relationship was ideally obtained between the ratio of the absorbance intensity at 620 nm to that at 520 nm (A(620)/A(520)). The linear response range, the detection, and quantification limit was 34.9-418.3 mu g/L and 7.6 mu g/L, and 25 mu g/L, respectively. To reflect the accuracy, the developed sensing approach was evaluated against certified reference materials (TMDA 51.3 fortified water and TMDA 28.3 fortified water). This colorimetric strategy was displayed excellent selectivity for Ga(III) over other examined ions. Additionally, the colorimetric method was properly used to detect the concentrations of Ga in tap water and certified reference material samples with recoveries ranging from 95.4 to 102.0%, displaying that the colorimetric procedure could be safely used for a realistic application

Neutral red interlinked gold nanoparticles/multiwalled carbon nanotubes modified electrochemical sensor for simultaneous speciation and detection of chromium (VI) and vanadium (V) in water samples

An electrochemical separation procedure has been developed for the speciation of Cr(VI) and V(V) in water samples. The sensing technique was based on the direct linear sweep voltammetric reduction of Cr(VI) and V(V) on a multi-walled carbon nanotube-neutral red-gold nanoparticles (MWCNTs-NR-AuNPs) modified commercially available screen-printed carbon electrode (SPCE). In this study, MWCNTs attached on the surfaces of NR-AuNPs via the covalent bonding between the carboxylic acid of MWCNTs and the free amine group of neutral red. The peak to peak separation of V(V) and Cr(VI) was about 269 mV, Total chromium and vanadium were determined after oxidation of Cr (III) to Cr(VI) and V(IV) to V(V) by potassium permanganate oxidation. The linear range of Cr(VI) and V(V) was 0.4-80 mu M and 3-200 mu M with the detection limits of 0.025 mu M and 0.42 mu M (S/N = 3), respectively. The recoveries of Cr(VI), Cr(III), V(V) and V(IV) were 97-99%, 96-98%, 97-99% and 95-98%, respectively, HorRat were calculated to 0.60-0.91 for Cr(VI), 0.55-1.11 for Cr(III), 50-1.16 for V(V) and 0.63-1.23 for V(IV), respectively. The proposed electrochemical separation procedure shows appropriate sensitivity and offers an alternative to the simultaneous detection and speciation of target metal ions

Simultaneous Determination of Fat-Soluble Vitamins by Using Modified Glassy Carbon Electrode

This study demonstrates the development of an electrochemical sensor based on beta-cyclodextrin/multi-wall carbon nanotubes modified glassy carbon electrode for detecting fat-soluble vitamins (vitamin A, vitamin D-3, vitamin E and vitamin K-1) in an aqueous media of micellar solutions using voltammetric studies. The linear calibration curves were 8-100, 0.8-60, 0.5-60 and 0.1-20 mu M for vitamin A, vitamin D-3, vitamin E and vitamin K-1, respectively. The optimal conditions for quantitative determination were obtained in a Britton-Robinson buffer at pH 5.0. Moreover, it is found that beta-cyclodextrin/multi-wall carbon nanotubes displays high reproducibility and selectivity for the determination of fat-soluble vitamins. The proposed voltammetric method permits the rapid and simple simultaneous electrochemical determination of fat-soluble vitamins. In this study, we used a sample pre-treatment methods, liquid-liquid extraction with hexane. At the end of the study, the proposed approach was applied to the electrochemical simultaneous determination of the mixed pharmaceutical sample and milk sample

Electrochemical and Electrochemiluminescence Dendrimer-based Nanostructured Immunosensors for Tumor Marker Detection: A Review

The usage of dendrimers or cascade molecules in the biomedical area has recently attracted much attention worldwide. Furthermore, dendrimers are interesting in clinical and pre-clinical applications due to their unique characteristics. Cancer is one of the most widespread challenges and important diseases, which has the highest mortality rate. In this review, the recent advances and developments (from 2009 up to 2019) in the field of electrochemical and electroluminescence immunosensors for detection of the cancer markers are presented. Moreover, this review covers the basic fabrication principles and types of electrochemical and electrochemiluminescence dendrimer-based immunosensors. In this review, we have categorized the current dendrimer based-electrochemical/ electroluminescence immunosensors into five groups: dendrimer/ magnetic particles, dendrimer/ferrocene, dendrimer/metal nanoparticles, thiol-containing dendrimer, and dendrimer/quantum dots based-immunosensors

Multi-Walled Carbon Nanotubes Magnetic Composite as an Adsorbent for Preconcentration and Determination of Trace Level Vanadium in Water Samples

Magnetic solid phase microextraction (m-SPME) is a well-defined strategy for the preconcentration and separation of hydrophobic species from aqueous samples without the use of toxic organic solvents. This work identifies a new analytical procedure for trace level vanadium(V) by inductively coupled plasma mass spectrometry coupled to magnetic solid phase microextraction. The procedure is based on the preconcentration of the V(V)-H2O2-4-(2-pyridylazo)resorcinol complex. Magnetic Fe3O4 nanoparticles decorated multi-walled carbon nanotubes as an adsorbent were investigated systematically. The calibration curve obtained by using m-SPME for vanadium(V) was linear from 0.011 to 10 mu g/L-. The method detection limit was found to be 1.5 ng/L. The m-SPME method was applied to the assay of vanadium in a certified reference water sample and the result was in total balance with the declared value. Finally, the proposed method was applied to the determination of vanadium in real water samples

Review on applications of carbon nanomaterials for simultaneous electrochemical sensing of environmental contaminant dihydroxybenzene isomers

Carbonaceous nanostructures stand out as an excellent electrode material to enhance the electrocatalytic, electroconductivity, and long-term stability of the electrochemical sensor in recent years. This review article focus on the important advancement in developing carbonaceous nanomaterials-based electrochemical sensors for simultaneous electrochemical sensing (binary and ternary mixtures) of environmental contaminants dihydroxybenzene isomers. The fabrication of electrochemical sensors such as graphene/carbon nanotubes hybrid composite, graphene/carbon nanotubes supported nanomaterials, mesoporous carbon, carbon nanofiber, carbon nano-fragment and biochar modified electrode was presented coupled with suitable applications. This review discussed the selective reports on the application of dihydroxybenzene sensors during the period from 2015 to 2020. (C) 2020 The Authors. Published by Elsevier B.V. on behalf of King Saud University. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/)

Electrochemical immunosensors for the detection of cytokine tumor necrosis factor alpha: A review

In this review, we focus on recent developments in nonlabeled@label-free and labeled@sandwich assay concepts of tumor necrosis factor-alpha (TNF-alpha) using numerous electrochemical approaches. The fundamental role of such nanostructured materials for the improvement of the analytical response and thus the analytical figures of merit of various TNF-alpha sensing operations were revealed. Also, this examination focused on recent developments in immuno-electrochemical cytokine TNF-alpha sensors based on nanostructured materials from 2006 to 2019

Dispersive Liquid-Liquid Microextraction Based on Ionic Liquid and Spectrophotometric Determination of Bilirubin in Biological Samples

Background: An Ionic Liquid-based based Dispersive Liquid-Liquid Microextraction (IL-DLLME) method was not applied to preconcentration and determination of bilirubin. Ionic Liquids (ILs) are new chemical compounds. In recent years, Ionic Liquids (ILs) have been employed as alternative solvents to toxic organic solvents. Due to these perfect properties, ILs have already been applied in many analytical extraction processes, presenting high extraction yield and selectivity for analytes

New Trends in the Pharmacological Intervention of PPARs in Obesity:Role of NAtural and Synthetic Compounds

Obesity is a major health concern for a growing fraction of the population, as its pre-valence and related metabolic disorders are not fully understood. Over the last decade, many at-tempts have been undertaken to understand the mechanisms at the basis of this condition, in which the accumulation of fat occurring in adipose tissue leads to the pathogenesis of obesi-ty-related disorders. Among the most recent studies, those on Peroxisome Proliferator Activat-ed Receptors (PPARs) revealed that these nuclear receptor proteins acting as transcription fac-tors, among others, regulate the expression of genes involved in energy, lipid, and glucose metabolisms, and chronic inflammation. The three different isotypes of PPARs, with different tissue expression and ligand binding specificity, exert similar or overlapping functions directly or indirectly linked to obesity. In this study, we reviewed the available scientific reports con-cerning the PPARs structure and functions, especially in obesity, considering both natural and synthetic ligands and their role in the therapy of obesity and obesity-associated disorders. On the whole, the collected data suggest that there are both natural and synthetic compounds that show beneficial and promising activity as PPAR agonists in chronic diseases related to obesity

Solid-phase extraction of Cr(VI) with magnetic melamine?formaldehyde resins, followed by its colorimetric sensing using gold nanoparticles modified with p-amino hippuric acid

A new method for magnetic solid-phase separation of trace-levels of Cr(VI) by using magnetic nanoparticles modified melamine?formaldehyde resin (Fe3O4@MFR) was described. Also, the selective and sensitive chemical optical probe was developed based on citrate-polyvinyl alcohol capped gold nanoparticle and modified with the reagent p-amino hippuric acid (PAH). Consequently, the optical probe was employed for the sensing of Cr(VI) ion in aqueous media. The sensing scheme is based on the complexation between PAH and reduced Cr(III). The linear calibration curve for Cr(VI) was calculated with preconcentration and was found in the range of 2.6?156 ?g L-1 and the limits of detection for Cr(VI) were 10.4 ?g L-1 and 2.0 ?g L-1 with the naked eye and UV?vis spectroscopic detection, respectively. More importantly, both magnetic solid-phase extraction and colorimetric optical probe are selective for detection of the target analyte. The recoveries are between 96 and 99% when exercising 15 mg of the Fe3O4@MFR. The coupled approach was employed for the pre-concentration and quantification of Cr(VI) in two real water samples (tap water and mineral water) employing the standard addition protocol