Method CARB 426

Determination of Cyanide Emissions from Stationary Sources

Particulate and gaseous phase emissions are extracted isokinetically from the stack and passed through a sampling train consisting of a heated probe and filter holder, glass fiber filter, and a series of impingers filled with NaOH.  Cyanide is collected on the filter and in the impinger solution.  The samples are analyzed for cyanide using titration or colorimetric determination.

Sulfides are known to cause interferences with the analysis.

The first and second impingers of the sampling train are filled with 100mL of 0.1N NaOH (sodium hydroxide), the third impinger is left empty, and the fourth is filled with 200-300g of silica gel which will be used for the moisture calculation.

NOTE that the pH of the impinger solutions must be checked prior to recovery to ensure the testing was valid.  The pH during this check must be basic for it to be considered a valid run.

After collection, the filter is placed in Container 1, a glass bottle with 50mL of 0.1N NaOH.  All  visible particulates are carefully transferred to the container as well.   Preserve Container 1 with 2mL 10N NaOH per L of solution and check to ensure the pH is ≥ 12The probe, nozzle, liner and front half of the filter holder is rinsed with 0.1N NaOH and put into Container 2, a glass bottle.  Preserve Container 2 with 2mL 10N NaOH per L of solution and check to ensure the pH is ≥ 12The silica gel from impinger 4 is placed in Container 3 for the moisture calculation.  The contents of the impingers are placed in Container 4 and the volume is recorded.  The contents of first and second impingers are combined with 0.1N NaOH rinses of the glassware.  The solution is preserved with 2mL 10N NaOH per L of solution checked to ensure the pH is ≥ 12.   Mark the liquid levels of all containers before shippment to the laboratory.

The filter, rinses, impinger contents are combined for analysis.  The sample is distilled and analyzed using either titration or colormetric determination for cyanide.  The titration method is good for concentrations of cyanide above 1mg/L and the detection limit is typically 0.3 mg/L.  The colorimetric method is good for cyanide concentrations from 0.02-1 mg/L and has a detection limit 0.01 mg/L.


(CARB Stationary Source Test Methods, Volume 3)


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Method Data

Hold Times, Preservatives, Preps, Collection, Analytical & Documentation
Holding Time:   None specified in the method.
Preservatives:   Preserve impinger contents after collection with 2mL of 10N NaOH per liter.
Required Preps:   Glass fiber filter
Collection Method:   Impinger train following CARB 426 procedures.
Analytical Methodology:   Titration or colorimetric determination
Documentation:   CARB 426

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.