Direct Spectrophotometric Measurements of Acid-catalyzed Complexation of Palladium(II) with 2-(5-Bromo-2-pyridylazo)-5-diethylaminophenol at the Heptane/Water Interface by a Centrifugal Liquid Membrane Method

• Published in: Analytical Sciences Vol. 17; no. 11; pp. 1313 - 1319
• Main Authors: OHASHI, Akira, WATARAI, Hitoshi
• Format: Journal Article
• Language: English
• Published: Tokyo The Japan Society for Analytical Chemistry 01-11-2001; Japan Society for Analytical Chemistry; Japan Science and Technology Agency
• Subjects: Analytical chemistry; Chemistry; Exact sciences and technology; Spectrometric and optical methods; Chemical analysis; Palladium Complexes; Association constant; Organic ligand; Visible spectrometry; Stability constant; Liquid membrane; Transition metal Complexes; Acid catalysis; Chemical enrichment; Membrane separation; Visual colorimetry; Liquid liquid interface; Centrifugal force; Platinoid Complexes; Kinetic parameter; Chemical properties; Quantitative analysis
• ISSN: 0910-6340; 1348-2246
• DOI: 10.2116/analsci.17.1313

The centrifugal liquid membrane (CLM) method, designed for the rapid sample injection, was applied to the kinetic study of the complexation of palladium(II) with 2-(5-bromo-2-pyridylazo)-5-diethyaminophenol (5-Br-PADAP) in the heptane/water system. The formation rates of Pd(II)-5-Br-PADAP complex, which existed only at the heptane/water interface, could be directly measured by the CLM method combined with transmission spectrophotometry. We found that the formation rates of Pd(II)-5-Br-PADAP complex were accelerated by the protonation of 5-Br-PADAP at the diethylamino-group that did not coordinate to Pd(II) ion and that the rate constant for the reaction of protonated 5-Br-PADAP at the interface was close to that in the aqueous phase. The present study demonstrated that the CLM method was easily applicable for the measurements of relatively fast interfacial reactions.