USGS Test Method I-2302

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Method Name:
Cyanide, whole water recoverable; colorimetric. Official Name: Cyanide, colorimetric, barbituric acid, automated-segmented flow

This method is based on the chlorination of cyanide with chloramine-T and on the subsequent reaction with a pyridine-barbituric acid reagent (Goulden and others, 1972). This method detects simple cyanides only; therefore, any complex cyanides must first be broken down by passing the acidified sample solution through an ultraviolet digestion-distillation procedure. The distillation step also removes certain interferences.

This method may be used to analyze water and water-suspended sediment containing from 0.01 to 0.30 mg/L cyanide. Samples containing more than 0.30 mg/L need to be diluted. Total recoverable cyanide in water-suspended sediment can be determined if each sample is shaken vigorously and a suitable aliquot of well-mixed sample withdrawn. This method may be used to determine cyanide in bottom material containing at least 0.5 mg/kg.

Methods for the Determination of Inorganic Substances in Water and Fluvial Sediments, Techniques of Water-Resources Investigations of the United States Geological Survey, Book 5, Chapter A1 Edited by Marvin J. Fishman and Linda C. Friedman

Chloride interferes if its concentration exceeds 3,000 mg/L. Oxidizing agents may interfere. Glycine and urea at the 10-mg/L level do not interfere. A concentration of 10 mg/L sulfide increases the apparent cyanide concentration by approx 0.02 mg/L. Concentrations of sulfide greater than 10 mg/L interfere considerably. Thiocyanate is broken down to cyanide and sulfide by this procedure and, therefore, interferes on an equimolar basis. Sulfate concentrations of 4,000 mg/L do not interfere. Higher concentrations were not tested.

QC Requirements:
Calibrate instrument using calibration standards (CAL). Quality control samples (QCS) and laboratory blanks (LB) analyzed at a minimum of I each after every 10 samples

Maximum Holding Time:
180 days



0.010 - 0.30 mg/L



Revision Number:

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