Analytical application of the reaction system methylene blue B-K2S2O8 for the spectrophotometric kinetic determination of silver in citric buffer media

Abstract

A new, simple, rapid, sensitive and selective spectrophotometric kinetic method for Ag(I) traces determination at room temperature was elaborated in this paper. It is based on catalytic effect of silver ions upon the oxidation of methylene blue B (MBB) by K 2 S 2 O 8 (PPS) in citric buffer (BUF) solution. The method was confirmed by determination of Ag(I) in PbO. The obtained results were compared to those obtained by ICP-OES method and good agreement of results was found.The silver traces determination is present in analytical practice for a long time. At the first time silver was determined in the photographic materials and solutions for black and white films, silver-plating solutions and effluents. Recently, silver has also been analyzed in ayurvedic and other drugs and medicines, chemical substances, natural and waste water samples, electronics, flow-solders, white metals, ores, alloys, biological samples, etc. [1,3,4] The toxico-kinetics of silver is very complex: its ability to form organometalic compounds and chelate complexes with influence on the metabolic processes in living organisms is subject of investigations in biology and environmental studies.There are different methods for Ag(I) determination, like atomic absorption spectrometry (AAS) [1,2], capillary zone electrophoresis (CZE) [3], fluorimetric [4], high performance liquid chromatography (HPLC) [5], kinetic [16][17][18][19], flow injection analysis (FIA) [20], spectrophotometric [21-28], photometric, etc. Silver was also determined using PVC-membrane electrodes based on 18-crown-6 and dibenzo-18-crown-6 ethers [29].Kinetic methods for Ag(I) determination with spectrophotometric detection, are mainly based on catalytic effect of silver ions upon the reaction rate of oxidation of different reductors by K 2 S 2 O 8 or (NH 4 ) 2 S 2 O 8 [6][7][8][9][10][11][12][13][14][15]. So, silver was determined as a catalyst of Kongo red oxidation in the presence of 1,10-phenantroline as an activator [6], and oxidation of BAPDAB in the presence of 2,2-dipyridyl as an activator [7], oxidation of