engleski

Fluorescence Quenching of Antropogenic Fulvic Acid by Iridium(IV),

Fulvic acid belongs to the group of humic substances. It can be considered a macromolecular polymer with structure and characteristics that change along with its origins and humification processes. The binding of metal ions to humic substances is of great interest in the understanding of metal ion transport and speciation in natural waters and soils. Fulvic acid from the humus obtained in the Zagreb (Croatia) area was isolated by a previously described procedure [1]. The fluorescence of the fulvic acid was strongly quenched by iridium(IV), and the quenching was greatest at pH=4 (controled by universal buffer) at l(ex) =340 nm, l(em) =430 nm. The fluorescence quenching of fulvic acid by iridium (IV) in water has been carried out at room temperature with a view to understand the quenching mechanisms. The quenching was found to be appreciable and showed positive deviation in the Stern-Volmer plots. This possitive deviation was attributed to the static and dynamic quenching. According to the obtained results, it can be concluded that the reaction of iridium(IV) with fulvic acid can be applied for the detection of the low Ir(IV) concentrations in aqueous solutions. Decrease in the emission intensity was linearly proportional to the iridium(IV) concentration in the range 0.96–15.38 ug cm(-3) of iridium, if the concentration of fulvic acid was 31, 22 ug cm(-3). The relative standard deviations estimated from six independent determinations in samples of 4, 81 and 9.62 ug cm(–3) of iridium(IV) were 1, 35 and 1, 21 %, respectively. (1) S. Hiradate, T. Yonezawa, H. Takesako, Geoderma, 132 (2006) 196205.

Fulvic acid ; Iridium ; Fluorescence

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