The EDTA-based disk-combination tests are unreliable for the detection of MCR-mediated colistin-resistance in...

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...

A Faraday disk dynamo is a DC generator, producing an emf that is constant in time. It consists of a conducting disk that rotates with a constant angular velocity in the magnetic field, perpendicular to the disk's plane. The rotation of the disk causes a change in magnetic flux, which induces an emf, causing opposite charges to develop on the rim and in the center of the disk. The polarity of the induced emf can be determined by the direction of the magnetic field and the direction of the...

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...

Each EDTA molecule has six binding sites: four carboxyl groups and two amino groups. The fully protonated form of EDTA is represented as H6Y2+. However, it can exist in different forms, H5Y+, H4Y, H3Y−, H2Y2−, and HY3−, depending on the pH of the solution. In very basic solutions with pH > 10.17, the fully deprotonated form, Y4−, is the predominant species that readily complexes with metal ions in a 1:1 ratio.
For the equilibrium reaction of the metal with the...

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...

The EDTA titration types for metal ion analysis include direct titration, back-titration, and replacement titration.
Direct titration involves buffering the metal ion solution to the desired pH and directly titrating with standard EDTA until the endpoint. The optimum pH ensures a large conditional formation constant of metal−EDTA and visibility of the free indicator color in the solution. In addition, auxiliary complexing reagents are used to prevent the precipitation of metal hydroxides...