VALIDATION AND ESTIMATION OF UNCERTAINTY OF MEASUREMENT FOR THE DETERMINATION OF FREE/RECOVERABLE CYANIDE IN WATER BY MEANS OF A DISCRETE ANALYZER.

摘要

Free/recoverable cyanide is one of the determinants required to be monitored in drinking water. According to SANS 241: 2011, the acceptable limit of free cyanide in drinking water is 70 μg/l. A test method for the determination of free cyanide was developed, validated and found suitable for the purpose of analyzing potable water, river water, borehole water and final treated sewage water between 2 μg/l and 1000 μg/l. The analytical instrument that was used for this exercise was the Aquakem 250. This method is based on the conversion of free cyanide to cyanogen chloride in the presence of chloramine-T. The cyanogen chloride produced is then reacted with pyridine and barbituric acid to form a red-violet complex which is measured by a spectrophotometer at a wavelength of 575 nm.