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Δ E p vs. pH Plot as a Source of Information in Polarographic Studies of Kinetically Labile Metal Complexes at a Constant Ligand to Metal Ratio
Author(s) -
Zelić Marina
Publication year - 2002
Publication title -
electroanalysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.574
H-Index - 128
eISSN - 1521-4109
pISSN - 1040-0397
DOI - 10.1002/1521-4109(200210)14:18<1262::aid-elan1262>3.0.co;2-8
Subject(s) - lability , polarography , metal , ligand (biochemistry) , chemistry , constant (computer programming) , plot (graphics) , position (finance) , analytical chemistry (journal) , inorganic chemistry , chromatography , mathematics , computer science , organic chemistry , statistics , biochemistry , receptor , programming language , finance , economics
Taking into account that during polarographic measurements at a constant ligand to metal ratio and gradually increasing pH value, the slope of Δ E p vs. pH plot is sometimes used for identification of the major complex species in the solution, characteristics of the mentioned relationship were studied in more detail. Assuming reversibility of the electrode process, kinetic lability of all the complexes and absence of possible complications, such as surface activity of dissolved species, it was demonstrated (by model calculations) that the shape, slope(s) and position of Δ E p vs. pH plot are highly affected by different factors. Even in very simple examples such as systems of HL‐ML type numerous limitations (concerning the acceptable values of β 1 [L] t product, relative concentrations of free ligand and metal etc.) appear which can sometimes completely prevent the successful application of this diagnostic method for identification of the major complex species because experimental results obtained under usual laboratory conditions do not meet the criteria. If, however, the mentioned limitations are ignored completely erroneous results could be obtained.