Determination of stability constants of copper(I) chelates with 1,10-phenanthroline by thermal lensing

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Using investigations of the copper(I)-1,10-phenanthroline system as an example, it is shown that thermal lensing can be used for determining stability constants at a level of concentrations one-two orders of magnitude lower compared to conventional spectrophotometry, with better precision of measurements. The values of stability constants are logβ2 = 11.7 ± 0.7 without regard for stepwise chelation, and logK1 = 5.9 ± 0.3, logK2 = 5-4 ± 0-3. and logβ2 = 11.3 ± 0.6 taking into account stepwise chelation. It is shown that, when shifting from microgram to nanogram amounts of reactants in the determination of stability constants by thermal lensing, changes in the kinetic parameters of the reaction studied should be taken into account. The thermal-lens limit of detection of copper(I) is 2 × 10-8 M; the linear calibration range is 4 × 10-8-2 × 10-5 M (488.0 nm, pump power 120 mW). The data obtained were used for determining copper(I) in the hydrogen sulfide layer of the Baltic Sea. © 2001 MAIK "Nauka/Interperiodica".

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Journal of Analytical Chemistry

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