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Related Concept Videos

Extraction: Advanced Methods00:56

Extraction: Advanced Methods

Metal ions can be separated from one another by complexation with organic ligands–the chelating agent– to form uncharged chelates. Here, the chelating agent must contain hydrophobic groups and behave as a weak acid, losing a proton to bind with the metal. Since most organic ligands used in this process are insoluble or undergo oxidation in the aqueous phase, the chelating agent is initially added to the organic phase and extracted into the aqueous phase. The metal-ligand complex is formed in...
Masking and Demasking Agents01:19

Masking and Demasking Agents

EDTA titrations may necessitate masking and demasking agents to temporarily protect a particular metal ion in a mixture from the EDTA reaction. These agents facilitate the sequential analysis of the metal ions by forming stable complexes with some—but not all—metal ions during certain steps.
There are many masking agents, such as cyanide, fluoride, triethanolamine, thiourea, and 2,3-bis(sulfanyl)propan-1-ol (formerly 2,3-dimercapto-1-propanol), with the masking agent chosen based on the metal...
EDTA: Auxiliary Complexing Reagents01:26

EDTA: Auxiliary Complexing Reagents

EDTA titrations are usually carried out in highly basic conditions, where the fully deprotonated form of EDTA, Y4−, actively complexes with the free metal ions in the solution. Several metal ions precipitate as hydrous oxide (hydroxides, oxides, or oxyhydroxides) under these conditions, lowering the concentration of free metal ions in the solution. For this reason, auxiliary complexing agents or ligands such as ammonia, tartrate, citrate, or triethanolamine are used in EDTA titrations to...
Complexation Equilibria: The Chelate Effect01:19

Complexation Equilibria: The Chelate Effect

In complexation reactions, metal atoms or cations interact with ligands to form donor-acceptor adducts called metal complexes. Ligands that bind through one donor site are monodentate, ligands with two donor sites are bidentate, and those with more than two donor sites are polydentate ligands. For example, ethylene diamine is a bidentate ligand that binds through two nitrogen donor atoms, forming a five-membered ring. EDTA is a polydentate ligand that binds through four oxygen and two nitrogen...
EDTA: Chemistry and Properties01:22

EDTA: Chemistry and Properties

Polydentate ligands are most widely used in complexometric titrations because they form more stable complexes with the metal ions than mono- or bidentate ligands due to the chelate effect. Examples of polydentate ligands are ethylenediaminetetraacetic acid (EDTA), crown ethers, and cryptands. The most important feature of optimal polydentate ligands is the ability to form 1:1 complexes in a single-step process. Amino carboxylic acid derivatives are frequently used as complexing agents. EDTA is...
Effects of EDTA on End-Point Detection Methods01:18

Effects of EDTA on End-Point Detection Methods

Different methods, such as visual observance of metal-ion indicators, spectroscopic techniques, and potentiometric methods, can determine the endpoint of an EDTA titration.
In the visual method, metal-ion indicators (metallochromic dyes), which have distinct colors in their free and complex forms, are added to the mixture to signal the titration's end point. They form stable complexes with metal ions, but these complexes are weaker than the corresponding metal–EDTA complexes. As a result, EDTA...

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An Anaerobic Biosensor Assay for the Detection of Mercury and Cadmium
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An Anaerobic Biosensor Assay for the Detection of Mercury and Cadmium

Published on: December 17, 2018

Interaction between human serum esterases and environmental metal compounds.

Antonio F Hernández1, Fernando Gil, Esther Leno

  • 1Department of Legal Medicine and Toxicology, University of Granada School of Medicine, Avda. Madrid, 11, 18071-Granada, Spain. ajerez@ugr.es

Neurotoxicology
|April 28, 2009
PubMed
Summary

Environmental metal exposure, including lead and mercury, significantly alters human serum esterase activities like Paraoxonase-1 (PON1) and cholinesterase (BChE). These findings highlight potential public health implications of heavy metal exposure on detoxification enzymes.

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Clean Sampling and Analysis of River and Estuarine Waters for Trace Metal Studies

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Area of Science:

  • Environmental Health
  • Biochemistry
  • Toxicology

Background:

  • Human serum esterases, Paraoxonase-1 (PON1) and cholinesterase (BChE), play crucial roles in detoxification.
  • While genetic factors influence PON1 activity, environmental chemicals are increasingly recognized as modulators.
  • Understanding environmental influences on these enzymes is vital for public health.

Purpose of the Study:

  • To investigate the influence of environmental exposure to metal compounds on PON1 and BChE activities.
  • To explore associations between serum esterase activities and levels of various metal compounds in a general population.

Main Methods:

  • Cross-sectional study of 536 healthy individuals from Andalusia, Spain.
  • Measurement of PON1 activity against multiple substrates (paraoxon, phenylacetate, diazoxon, dihydrocoumarin) and BChE in serum.
  • Analysis of associations with blood metal levels (lead, mercury, cadmium, zinc, arsenic, nickel, manganese), age, sex, BMI, and lifestyle factors using multiple linear regression.

Main Results:

  • Elevated blood lead levels were significantly associated with increased PON1 activity, irrespective of the substrate.
  • Mercury showed a direct association with PON1 activity towards paraoxon and phenylacetate.
  • Cadmium and zinc were significantly associated with decreased PON1 activity, while BChE was inversely associated with manganese and zinc.

Conclusions:

  • Background exposure to metal compounds significantly modulates PON1 and BChE activities in the general population.
  • These modulations may have public health implications due to the enzymes' roles in detoxifying environmental toxicants.
  • Further research is warranted to elucidate the underlying mechanisms of these enzyme-metal interactions.