Analytical Sciences

Abstract − Analytical Sciences, 20(9), 1333 (2004).

Spectrophotometric Studies of the Interaction of Noble Metals with Quercetin and Quercetin-5′-Sulfonic Acid
Maria BALCERZAK,* Maria KOPACZ,** Anna KOSIOREK,* Elzbieta SWIECICKA,* and Stanislaw KUS*
*Department of Analytical Chemistry, Warsaw University of Technology, Noakowskiego 3, 00-664 Warsaw, Poland
**Department of Inorganic and Analytical Chemistry, Rzeszow University of Technology, 35-959 Rzeszow, Poland
Results of some studies on the interaction of noble metals with quercetin (Q) and quercetin-5′-sulfonic acid (QSA), the compounds of flavonoid group, are presented. The reactions of chloride complexes of the metals: RuOHCl52-, PdCl42-, OsCl62-, PtCl62- and AuCl4- with both reagents were examined. The redox reactions of ruthenium and gold with Q and QSA have been identified. The reaction of the metals with both reagents results in the formation of the oxidized form of Q that exhibits maximum absorbance at 291 nm. Ruthenium and gold react with the examined reagents under similar conditions: 0.04 M HCl and 1 × 10-4 M Q (or QSA). The CH3OH + H2O (1:1) (Q) and pure aqueous (QSA) media can be used. The reaction of gold with Q is slow at room temperature. It can be accelerated by heating the solution being examined. The reaction proceeds significantly faster when the water-soluble sulfonic derivative of quercetin, quercetin-5′-sulfonic acid, is used as a reagent. The new species formed can make the basis of spectrophotometric methods for the determination of ruthenium and gold. The molar absorptivities at 291 nm are equal to 5.0 × 103 and 2.2 × 104 L mol-1 cm-1 for Ru and Au, respectively, independently of the reagent used. Some methods for the determination of the content of gold (0.04%) in a cosmetic cream were developed.