the IA and increase the pathlength of the absorbing cell without affecting the sensitivity
and reproducibility of the CPAT determination.
On the curve of ΔA versus pH for IA Bromcresol Purpur - CPAT, the differences
in the absorbance of the dye in the absence and in the presence of a polymer are
observed in the pH range from 3.7 to 5.2.
Similar changes were observed by us also by many other basic dyes, including
Erithrozine, Eozine, Brompyrogallol Red and Chromazurol S.
CONCLUSION
1. Changes in absorption spectra induced by aggregation forces are observed in
several systems, including ion associates formed between heteropoly anions and
organic dyes. It was shown at the first time that similar analytical effects are observed
by the formation specific of IAs of HPAs with all the represntatives of cationic dyes,
including rhodamine, triphenylmethane, polymethine and thiazine. Other systems
include IAs formed between iodide and rhodanide anionic metal complexes and basic
dyes.
2. Molar absorptivity of specific IAs is determined by two main factors. First one
is molar absorptivity of the dye, and second one the influence of the mutual
arrangement of dye ions in the IA on the redistribution of band intensities in the IA
formed. The most favorable changes in the spectra were observed for polymethine and
rhodamine dyes.
3. The changes of spectra by interaction of sulfonphtaleine dyes with cationic
polyelectrolytes are mainly explained by the shift of the acid-base equilibrium to the
most stable ion associate formed by polyelectrolyte with one of the protonated forms
of the dye. Aggregation of sulfonphtaleine dyes was shown for the first time for the
interaction of them with cationic polyelectrolytes. Intensity of the band for aggregated
form of the dye depends on the charge density of polymer and increases for the polymer
having high charge density.
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determination of phosphorus by flow-injection techniques. Talanta 66 (2005) 332–340.
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inorganic phosphate. Clin. Chim. Acta 14 (1966) 361-366.
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