Determination of Attogram Quantities of Silver via Quenching of the Solid Substrate Room-Temperature Phosphorescence of Rhodamine B Based on the Catalysis of its Oxidation by Potassium Persulfate

Abstract.

A new method of SS-RTP for the determination of trace silver has been established. This method is based on the fact that Ag⁺, when activated by α,α′-bipyridyl (bipy) in a media of HAc–NaAc (pH = 4.9), can catalyze the reaction of Rhodamine B (RhoB) oxidized by K₂S₂O₈, thus causing the Solid Substrate Room-Temperature Phosphorescence (SS-RTP) of RhoB to be quenched. The activating efficiency of bipy is 6.7 times higher than that of o-phenanthroline (phen). The reduction of the phosphorescence intensity (ΔI_p) of RhoB is directly proportional to the concentration of Ag⁺ ions in the range of 1.60∼16.0 ag spot⁻¹ (0.40 µL spot⁻¹). The regression equation of the working curve can be expressed as ΔI_p = 18.78 + 5.100 m_Ag+ (ag spot⁻¹) (r = 0.9994, n = 6), the detection limit is 0.28 ag spot⁻¹. This rapid, accurate and sensitive method has been successfully applied to the determination of trace silver in tea and human hair samples, and the results agree well with the Atomic Absorption Spectroscopy (AAS) method. The mechanism of the catalyzing reaction is also discussed.