Voltametric determination of silver on a graphite electrode in spent fixative and bleaching fixative solutions

摘要

A dc voltametric method for rapid analysis of silver in used fixative solutions that is based on measurement of the peak of reduction of silver using a graphite electrode is proposed. The analysis is carried out in an undiluted solution (1-8 g/liter Ag) or in a fixative sample (1 - 30 g/liter Ag) 25 - 30-fold diluted with a background solution (0.1 M Na{sub}2S{sub}2O{sub}3+0.1 M Na{sub}2SO{sub}3). The increase in concentration of either Na{sub}2S{sub}2O{sub}3 or Na{sub}2SO{sub}3 to 0.3 M in the background solution does not affect the results of analysis. Other components of fixative solutions such as I{sub}-, Br{sub}-, (NO{sub}3){sup}-, (NH{sub}4){sup}+, complexones EDTA and CDTA, and citric and acetic acids do not interfere with the determination of silver. The calibration graph is linear and passes through the origin for sweep rates of 5 - 20 mV/sec. The results of voltametric analysis are checked for correctness by comparison with data obtained by the chemical method of Folgard; the relative standard deviation is 0.006 -0.02 for measurements conducted using a graphite electrode with mechanical renewal of the surface layer.