EPA Method 7470A

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View Actual EPA Method 7470A (PDF File)


EPA Method 7470A:
Mercury by Manual Cold-Vapor Technique. Official Name: Mercury in Liquid Waste (Manual Cold-Vapor Technique)

Summary:
Aqueous samples are digested with sulfuric acid, nitric acid, potassium permanganate, and potassium persulfate in order to oxidize the organo-mercury compounds to the mercuric ion. Once the digested samples have cooled, sodium chloride-hydroxylamine sulfate is added to reduce excess permanganate. Stannous sulfate is then added to the samples for the reduction to elemental mercury which is immediately measured by a cold-vapor atomic absorption spectrophotometer (or equivalent instrument).

Scope:
This method determines the concentration of mercury in aqueous wastes, mobility-procedure abstracts, and ground water. It can also be used for analyzing certain solid and sludge-type wastes, however, Method 7471 is recommended for these matrices.

Citation:
SW-846 Online: Test Methods for Evaluating Solid Waste, Physical/Chemical Methods

Interferences:
(A) Matrix interferences: Sulfide as sodium sulfide may possibly interfere with mercury, however, potassium permanganate is added to eliminate interferences from concentrations as high as 20 mg/L. Copper is also known to cause interference, however, concentrations as high as 10 mg/L have shown to have no effect on mercury recovery. Seawaters, brines, and industrial effluents high in chlorides require additional amounts of permanganate and hydroxylamine sulfate to ensure the absence of free chlorine which interfere with mercury detection. In addition, air space in the BOD bottle must be purged before adding stannous chloride. Certain volatile organic compounds may also cause interference. A preliminary run without reagents should determine their presence.

QC Requirements:
Refer to section 8.0 of Method 7000.

Maximum Holding Time:
Preserved samples: 28 days.

Media:
VARIOUS

Subcategory:
Inorganic

Concentration:
Not Available.

Sample Prep:
Method 7470A

Precision:
See EPA Method 245.1

Detection:
None.

Revision Number:
Revision 1, September 1994

Test Description:
Mercury in Liquid Waste (Manual Cold-Vapor Technique)

Instrument used for this test:
CVAA