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A complexometric indicator is an ionochromic dye that undergoes a definite color change in presence of specific metal ions. [1] It forms a weak complex with the ions present in the solution, which has a significantly different color from the form existing outside the complex. Complexometric indicators are also known as pM indicators.
A metal ion in aqueous solution or aqua ion is a cation, dissolved in water, of chemical formula [M(H 2 O) n] z+. The solvation number , n , determined by a variety of experimental methods is 4 for Li + and Be 2+ and 6 for most elements in periods 3 and 4 of the periodic table .
According to their properties, cations are usually classified into six groups. [1] Each group has a common reagent which can be used to separate them from the solution.To obtain meaningful results, the separation must be done in the sequence specified below, as some ions of an earlier group may also react with the reagent of a later group, causing ambiguity as to which ions are present.
The model is defined in terms of a list of those complex species which are present in solutions in significant amounts. In the present context the complex species have the general formula [M p O q (OH) r] n±. where p, q and r define the stoichiometry of the species and n± gives the electrical charge of the ion. The experimental data are ...
The mass of b 2-ion = mass of two amino acid residues + 1. Table 2. Mass of b2-ions in peptide fragmentation [16] Identify a sequence ion series by the same mass difference, which matches one of the amino acid residue masses (see Table 1). For example, mass differences between a n and a n-1, b n and b n-1, c n and c n-1 are the same.
A disadvantage of using alkali ions in place of noble gas ions is the increased likelihood of adsorption or deposition to the sample surface. Impact-collision ion scattering spectroscopy (ICISS) takes advantage of shadowing and blocking in order to make precise determinations about interatomic spacing of the first 1-2 layers in a surface. The ...
Identification of the molecular ion can be difficult. Examining organic compounds, the relative intensity of the molecular ion peak diminishes with branching and with increasing mass in a homologous series. In the spectrum for toluene for example, the molecular ion peak is located at 92 m/z corresponding to its molecular mass. Molecular ion ...
Similar tests for identifying organic compounds (by testing for different functional groups) are also known. Many techniques can be used for either qualitative or quantitative measurements. For instance, suppose an indicator solution changes color in the presence of a metal ion. It could be used as a qualitative test: does the indicator ...