Dispersive Liquid-Liquid Microextraction of Bismuth in Various Samples and Determination by Flame Atomic Absorption Spectrometry

A dispersive liquid-liquid microextraction method for the determination of bismuth in various samples by flame atomic absorption spectrometry is described. In this method, crystal violet was used as counter positive ion for BiCl4- complex ion, chloroform as extraction solvent, and ethanol as disperser solvent. The analytical parameters that may affect the extraction efficiency like acidity of sample, type and amount of extraction and disperser solvents, amount of ligand, and extraction time were studied in detail. The effect of interfering ions on the analyte recovery was also investigated. The calibration graph was linear in the range of 0.040–1.00 mg L−1 with detection limit of 4.0 μg L−1 (n=13). The precision as relative standard deviation was 3% (n=11, 0.20 mg L−1) and the enrichment factor was 74. The developed method was applied successfully for the determination of bismuth in various water, pharmaceutical, and cosmetic samples and the certified reference material (TMDA-64 lake water)

Dispersive Liquid-Liquid Microextraction of Bismuth in Various Samples and Determination by Flame Atomic Absorption Spectrometry

A dispersive liquid-liquid microextraction method for the determination of bismuth in various samples by flame atomic absorption spectrometry is described. In this method, crystal violet was used as counter positive ion for BiCl 4 − complex ion, chloroform as extraction solvent, and ethanol as disperser solvent. The analytical parameters that may affect the extraction efficiency like acidity of sample, type and amount of extraction and disperser solvents, amount of ligand, and extraction time were studied in detail. The effect of interfering ions on the analyte recovery was also investigated. The calibration graph was linear in the range of 0.040-1.00 mg L −1 with detection limit of 4.0 g L −1 ( = 13). The precision as relative standard deviation was 3% ( = 11, 0.20 mg L −1 ) and the enrichment factor was 74. The developed method was applied successfully for the determination of bismuth in various water, pharmaceutical, and cosmetic samples and the certified reference material (TMDA-64 lake water)

Zirconium in modern analytical chemistry

Detailed monographs on the analytical chemistry of zirconium, which is widely used in all fields of modern science and technology, were published in the 1960s-1970s of the last century. This review summarizes information on the modern methods for determination of zirconium in a great variety of natural, technical, and biological objects. Focus is made on the works published in scientific periodicals after 2005. Spectroscopic techniques of zirconium determination including molecular and atomic spectrometry, X-ray fluorescence analysis, and electrochemical and activation methods are described. The paper also describes the applications of zirconium compounds, in particular, in analytical chemistry. © 2018 Walter de Gruyter GmbH, Berlin/Boston

Electroanalytical overview: The detection of chromium

Chromium exerts serious damage to human beings and to aquatic life and is one of the most common environmental contaminant and possess toxicity when present above threshold limits. In comparison with the traditional quantification methods such as atomic absorption spectroscopy (AAS), inductively coupled plasma mass spectrometry, UV-Vis or high-performance liquid chromatography, electrochemical methods towards monitoring chromium ions have the advantages of being portable, rapid, cost effective, simple, sensitive and selective enough to meet regulatory limits. This review presents the recent progress in the field of electroanalysis using different electrode platforms such as solid or screen-printed electrode (SPE) and various functional materials towards chromium determination. The fabrication strategy and the analytical performance of carbon nanomaterials (such as carbon nanotubes and graphene), metal and metal oxide nanomaterials enabled sensors for electrochemical determination of chromium (III) and chromium (VI) ions are summarized systematically. In addition, method validation and the application of these sensors in real samples for the analysis of chromium ions is discussed and future developments in this domain are provided

Amperometric determination of selected persistent organic pollutants and heavy metals using horseradish peroxidase biosensor.

Thesis (M.Sc.)-University of KwaZulu-Natal, Durban, 2010.Persistent organic pollutants and heavy metals are released into the environment through different anthropogenic processes. They are of concern because they tend to bioaccumulate in the food chain and show adverse health effects ranging from acute to chronic toxicity. These pollutants need therefore to be monitored to conserve the environment. Conventionally, samples are sent to a laboratory for analysis by standard techniques such as chromatography and spectroscopy. Although these conventional techniques display high accuracy and low detection limits, they are expensive, require the use of highly trained personnel and tedious sample preparation. In comparison, electrochemical methods such as biosensors are sensitive, low cost and simple to operate. In this thesis, the determination of selected persistent organic pollutants (polybrominated diphenyl ethers, polybrominated biphenyls and polychlorinated biphenyls) and heavy metals (Cd, Pb and Cu) was achieved by the use of amperometric inhibition biosensor based on horseradish peroxidase (HRP) immobilized on the surface of platinum-polyaniline modified electrode. Polyaniline (PANI) film was electrochemically deposited on the platinum electrode surface. The film was characterized by cyclic voltammetry and spectrometric techniques. The CV results proved that the PANI was electroactive and exhibited a fast reversible electrochemistry. Characteristic Ultraviolet–Visible and Fourier Transform Infrared features of the polymer film were identified. They revealed that PANI film synthesized in this study is the conductive emeraldine salt. Horseradish peroxidase based biosensor was constructed by electrostatic attachment of the enzyme onto Pt-PANI electrode surface. Spectrometric and cyclic voltammetric results indicated that the immobilized HRP retained its bioelectrocatalytic activity towards the reduction of hydrogen peroxide. The Pt/PANI/HRP biosensor showed a linear response over a concentration range of 0.05 to 3.17 mM with a detection limit of 36.8 nM. Apparent Michaelis- Menten constant ( app M K ) was calculated as 1.04 mM. This implied that the HRP biosensor had a high affinity for H2O2. Furthermore, the fabricated biosensor showed high sensitivity, good reproducibility, repeatability and long-term stability. The Pt/PANI/HRP biosensor was applied to the determination of selected persistent organic pollutants and heavy metals. The latter was found to inhibit the HRP enzyme’s activity. The percentage inhibition of the investigated persistent organic pollutants decreases in the following order: 2,2´4,4´,6-pentabrominated diphenyl ether> 2-brominated biphenyl> 2-chlorinated biphenyl> 2,2´,4,5,5´-pentachlorinated biphenyl> 2,4,4´-trichlorinated biphenyl. In the case of heavy metals, the degree of inhibition of heavy metals was highest for Cd2+, followed by Cu2+ and then Pb2+. Kinetic study for the amperometric response to H2O2, recorded in the absence and presence of persistent organic pollutants and heavy metals revealed that for polybrominated diphenyl ethers, the inhibition process corresponded to a competitive type whereas for polybrominated biphenyls, polychlorinated biphenyls and heavy metals, it corresponded to the on-competitive type. The biosensor exhibited high sensitivity towards the determination of the metals and persistent organic pollutants as pollutants in real water samples, namely tap water and landfill leachate samples

Investigation of Volatile Organic Compounds (VOCs) released as a result of spoilage in whole broccoli, carrots, onions and potatoes with HS-SPME and GC-MS

Vegetable spoilage renders a product undesirable due to changes in sensory characteristics. The aim of this study was to investigate the change in the fingerprint of VOC composition that occur as a result of spoilage in broccoli, carrots, onions and potatoes. SPME and GC-MS techniques were used to identify and determine the relative abundance of VOC associated with both fresh and spoilt vegetables. Although a number of similar compounds were detected in varying quantities in the headspace of fresh and spoilt samples, certain compounds which were detected in the headspace of spoilt vegetables were however absent in fresh samples. Analysis of the headspace of fresh vegetables indicated the presence of a variety of alkanes, alkenes and terpenes. Among VOCs identified in the spoilt samples were dimethyl disulphide and dimethyl sulphide in broccoli; Ethyl propanoate and Butyl acetate in carrots; 1-Propanethioland 2-Hexyl-5-methyl-3(2H)-furanone in onions; and 2, 3-Butanediol in potatoes. The overall results of this study indicate the presence of VOCs that can serve as potential biomarkers for early detection of quality deterioration and in turn enhance operational and quality control decisions in the vegetable industry

Analysis of 17- β -estradiol and 17- α -ethinylestradiol in biological and environmental matrices — A review

The estrogens 17-β-estradiol (E2) and 17-α-ethinylestradiol (EE2) are reported as highly endocrine-disrupting agents, being recently included in an EU watch list regarding emerging aquatic pollutants. Therefore, the monitoring of these chemicals in the different environmental compartments assumes great importance. Moreover, due to the possible adverse effects on living beings, their occurrence on animal tissues and fluids must also be addressed. In recent years, a significant number of studies have described and proposed different analytical methodologies to detect and/or quantify E2 and EE2 mostly in environmental aqueous samples, including sludge and sediments and also in biological matrices such as plasma and tissues. Taking into account the complexity of real matrices and that both estrogens are generally present at trace levels, the development of accurate and reliable techniques for their determination can be quite a challenge. The present review aims at describing the main characteristics of the analytical methods recently used for E2 and EE2 determination in environmental and biological samples. The steps for sample preparation such as analytes extraction, preconcentration and clean-up are discussed and the instrumental based analytical techniques are compared. Furthermore, the application of biological tools to determine the total estrogenicity of environmental samples, as well as their potential combination with instrumental analyses, is highlighted.info:eu-repo/semantics/publishedVersio

Arsenic Monitoring, Removal and Remediation

Arsenic Monitoring, Removal and Remediation discusses methods for determining arsenic levels in the environment and removing arsenic pollution. Chapters in the first section comment on the principal methods for arsenic determination in environmental samples with emphasis on sample pretreatment, extraction, separation, and method validation techniques for speciation analysis. Attention is paid to the electrochemical methods for arsenic quantification as an alternative to the commonly used techniques and to the potential of the differential alternative pulses voltammetry for arsenic determination in the presence of interferences. Chapters in the second section highlight the benefits of using adsorption for arsenic species removal and suggest remedial approaches against arsenic pollution, including bioremediation, along with traditional techniques

Development of electrochemical biosensors and sensors for the determination of interest analytes

Se han puesto a punto varios métodos electroquímicos para la determinación de varios analitos de interés, como lactato, cloruro, bromuro y yoduro utilizando sistemas electródicos serigrafiados (SPEs). Su bajo costo, tamaño pequeño, portabilidad para aplicaciones in situ, así como su facilidad de modificación, les confiere gran versatilidad, para ser usados como transductores en sensores y biosensores electroquímicos con gran precisión y sensibilidad en distintas matrices. Concretamente, se ha desarrollado un biosensor amperométrico para la determinación de lactato, basado en la utilización de la enzima lactato oxidasa. El biosensor ha permitido la determinación de este ácido orgánico en líquidos biológicos como saliva y sudor y en productos alimentarios como vinos. Se incluyen también estudios de los mecanismos de inhibición de las enzimas utilizadas en los biosensores. También se han puesto a punto sensores para la determinación de haluros, que han mostrado su aplicabilidad para su cuantificación en varios tipos de muestras