Method 335.4

Determination of Total Cyanide by Semi-automated Colorimetry

This method is for the determination of cyanide in drinking, ground, surface, and saline waters, domestic and industrial wastes.  The applicable range is 5 to 500 µg/L.

Cyanide as hydrocyanic acid (HCN) is released from cyanide complexes by a manual reflux-distillation and absorbed in a sodium hydroxide scrubber solution.  The cyanide ion in the aborbing solution is converted to cyanogen chloride by reactions with chloramine-T that reacts with pyridine and barbituric acid to form a red-colored complex which is anlayzed by a colorimeter.

Sulfides is a known interference as it produces hydrogen sulfide during the distillation.  Nitrates and nitrites may give results a high bias as the distillation step will form oximes which can decompose to form HCN. Oxidizing agents such as chlorine can decompose most of the cyanides.

(EPA: Office of Water)


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Method Data

Hold Times, Preservatives, Preps, Collection, Analytical & Documentation
Holding Time:   14 days from sample collection to analysis. Analysis as soon as possible is recommended.
Preservatives:   Preserve to pH <12 and store at 4°C.
Required Preps:   250mL poly or glass bottle.
Collection Method:   Grab sampling
Analytical Methodology:   Colorimetry
Documentation:   335.4

Analyte List*

Analyte Formula CAS Number Detection Limit
Total Cyanide

* The analytes and detection limits listed for each method represent the typical detection limits and analytes reported for that particular method. Keep in mind that analyte lists may vary from laboratory to laboratory. Detection limits may also vary from lab to lab and are dependent upon the sample size, matrix, and any interferences that may be present in the sample.