Analytical Sciences

Flow Injection Spectrophotometric Determination of Sub-mg dm⁻³ Silver(I) in a Strongly Acidic Solution Containing Concentrated Copper(II) Using a Pyridylazo Reagent

Kazuyoshi FUJIMURA,* Tamao ODAKE,** Hiromi TAKIGUCHI,** Noriyuki WATANABE,* and Tsuguo SAWADA*

*Department of Applied Chemistry, School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-8656, Japan
**Safety and Health Office, School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-8656, Japan

A novel spectrophotometric flow injection method for determination of silver(I) in a strongly acidic solution containing concentrated copper(II) was developed using a coloring ligand, 4-(3,5-dibromo-2-pyridylazo)-N-ethyl-N-(3-sulfopropyl)aniline (3,5-diBr-PAESA). The method was first investigated by batch method. The interference from copper(II) chelate could be eliminated by the masking effect of EDTA. By utilizing the large formation constant (K = 12.3) of AgBr, one could determine silver(I) as a decrease of absorption by silver(I) chelate due to formation of AgBr by addition of KBr. Based on the results of batch experiments, two types of flow injection analysis (FIA) systems were constructed. Sub-mg dm⁻³ determination of silver(I) was attained without interference from excess copper(II). The proposed method was successfully applied to determination of silver in a copper plating solution used in a plant to manufacture copper printed circuit boards, where the concentration of silver was critically important in the process control.

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