Micelle Mediated Trace Level Sulfide Quantification through Cloud Point Extraction

A simple cloud point extraction protocol has been proposed for the quantification of sulfide at trace level. The method is based on the reduction of iron (III) to iron (II) by the sulfide and the subsequent complexation of metal ion with nitroso-R salt in alkaline medium. The resulting green-colored complex was extracted through cloud point formation using cationic surfactant, that is, cetylpyridinium chloride, and the obtained surfactant phase was homogenized by ethanol before its absorbance measurement at 710 nm. The reaction variables like metal ion, ligand, surfactant concentration, and medium pH on the cloud point extraction of the metal-ligand complex have been optimized. The interference effect of the common anions and cations was studied. The proposed method has been successfully applied to quantify the trace level sulfide in the leachate samples of the landfill and water samples from bore wells and ponds. The validity of the proposed method has been studied by spiking the samples with known quantities of sulfide as well as comparing with the results obtained by the standard method

Electrochemical Investigation of Porphyrin and Its Derivatives at Various Interfaces

This chapter describes the electrochemistry of the porphyrins at solid‐liquid and liquid‐liquid interfaces. The fundamental electrochemical approach toward the porphyrin molecules in estimating their HOMO and LUMO energy levels is given. Various factors such as the effect of central metal ion, the periphery of the aromatic ring and axial ligands on the redox potentials of porphyrins have been discussed. Electrochemical sensing application of porphyrin molecules is described with few examples in brief. Much focus has been given on the electrochemistry of the self‐assembled monolayer (SAM) of thiol‐porphyrins on the gold electrode. Structural characterization and charge transfer across the SAM using cyclic voltammetry and electrochemical impedance spectroscopy are discussed. Theory and methodologies developed to study photoinduced charge transfer kinetics of porphyrin molecules using scanning electrochemical microscope at the solid‐liquid and liquid‐liquid interface have been described. Use of porphyrin molecules as luminophores in electrochemiluminescence sensing applications and the mechanisms involved are described through representative examples

Electrochemical and Optical Methods for the Quantification of Lead and Other Heavy Metal Ions in Liquid Samples

Minerals and elementary compounds of heavy metals are part of the ecosystem. Because of their high density and property to accumulate in stable forms, they are considered to be highly toxic to animals, plants and humans. Continuous mining activities and industrial effluents are the major sources which are adding toxic heavy metal ions into ecosystem and biota. Hence it is of utmost importance to quantify the levels of heavy metal ions in environmental and biological samples. On the other hand, it is equally important to remove the heavy metal ions and their compounds from the environmental and biological samples. That facilitates the environmental samples to be fit for using, consumption. In this regard, promising quantification methods such as electrochemical, spectrophotometric, naked eye sensing, test strips for spot analysis of heavy metal ions are considered for discussion. The main objective of this chapter is to give the overview of the most practiced quantification approaches available in the literature. Please note that reader cannot find the pin to pin publications regarding the same and that is not the aim of this book chapter

A novel mixed matrix membrane of phenolphthalein hydrazide and polysulfone for the detection of copper ions in environmental water samples.

The novel membrane test strip of phenolphthalein hydrazide (PH)-polysulfone has been designed and demonstrated for Cu2+ ions detection. Before finding performance of membrane the studies with PH alone has been performed. Aqueous solutions of PH are colorless, but upon interaction with Cu2+ ions become pink (when 8.2 ≤ pH ≥ 12). The colorimetric change is initiated by the coordination of Cu2+ with PH as a polydentate ligand, opening the spirolactam ring that subsequently hydrolyses releasing phenolphthalein (P). Further membrane was preloaded with PH that could be used as a simple, low cost, and portable sensor for Cu2+ ions in environmental water samples. Given the detection limits of this sensor, a maximum response would warn the tester that Cu2+ concentrations were above safe drinking regulation values. Approximate concentrations can be determined via a color comparison chart. Different metal ions were tested in order to determine the chemodosimeters specificity, of the 12 tested ions only Hg2+ induced a similar molecular transformation (i.e., PH to P). The chemodosimeter allows the quantification of Cu2+ ions in the linear dynamic range of 0–22 μM. The Sandell sensitivity, limit of detection, limit of quantification, and relative standard deviation were found to be 0.276 μg/mL/cm2, 0.279 μM, 1.674 μM, and 0.682% respectively

Size Reduced Iron Nitroprusside Particles: an Electrochemical Mediator for the Quantification of Peroxodisulfate and Nitrite

<div><p>Iron nitroprusside (FeNP) particles have been synthesized from drop by drop (n-FeNP) and bulk mixing (BM) (b-FeNP) methods. FeNP particles obtained from both methods were characterized using X-ray diffraction (XRD) and scanning electron microscopy (SEM). n-FeNP particles were used in constructing modified carbon paste electrode (CPE), which has been further used for electrochemical studies. The effect of pH and electrolyte cation on the electrochemical behavior of n-FeNP modified CPE has been studied in detail. Oxidation of nitrite and reduction of peroxodisulfate reactions have been electrocatalyzed at two redox centers of n-FeNP modified CPE. Based on the electrochemical experiments conducted and Tafel plots, mechanism for both the reactions has been proposed. Both the analytes were estimated in soil and ground water samples using n-FeNP modified CPE and the results were validated with the help of standard methods.</p></div

Bimodal Electrochemiluminescence of G‑CNQDs in the Presence of Double Coreactants for Ascorbic Acid Detection

How to improve the accuracy of target detection substance in low-content and complex of real sample, which is still a major challenge in the analysis field. There is no doubt that the internal standard method is the best choice in the analysis methods. The internal standard method of ECL strategy can furnish more accurate detection results in the changeable complex environment, and it can dispel the primary vaguest interference in the system through the self-calibration of two emission spectra. Herein, we effectually explored a strong and stable bimodal ECL system based on graphitic carbon nitride quantum dots (g-CNQDs) as single luminophore in the presence of double coreactants potassium persulfate (K₂S₂O₈) and tetrabutylammonium bromide (TBAB) under the optimized conditions. ECL-1 at 2.82 V and ECL-2 at 1.73 V were observed when the potential was scanned between −3 and 3 V at the scan rate of 0.2 V·s^–1. The ECL-1 was responding to the analyte, that is, ascorbic acid (AA) and the ECL-2 was not for a certain concentration of AA; hence, the developed bimodal ECL system was used as internal standard method for quantitative AA in human serum due to the different sensitivity of the double-peak ECL signals to the target analytes. The linear relationships were obtained based on the ln <i>I</i> (ECL-1/ECL-2) against the concentration of AA in the concentration range of 3.5 to 330 nM, with a detection limit of 110 pM (S/N = 3)

Behaviors of the Interfacial Consecutive Multistep Electron Transfer Controlled by Varied Transition Metal Ions in Porphyrin Cores

Almost all life activities involve the process of multistep electron transfer (ET) which occurs on biomembrane. Metalloporphyrins (MTPPs) are a class of molecules which are closely related to life course. Here, the <i>n</i>-step (<i>n</i> = 1, 2) ET behaviors controlled by different metal ions in porphyrin cores were investigated by thin-layer cyclic voltammetry (TLCV). The bimolecular ET was reacted between the MTPP (M = Fe, Zn, Co, Cu, Ni) and Fe­(CN)₆^4– in nitrobenzene and aqueous phase, respectively, and the interface between nitrobenzene and aqueous phase was considered as a bionic membrane. The thin-layer theory, which has been revised, was used to calculate the kinetic constants for each step electron transfer reactions. It was shown that the kinetic data were affected dramatically by the different coordinated ions in porphyrin complexes