EPA Method 7473

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EPA Method 7473:
Mercury in Solids and Solutions by Thermal Decomposition and AA . Official Name: Mercury in Solids and Solutions by Thermal Decomposition, Amalgamation, and Atomic Absorption Spectrophotometry

Controlled heating in an oxygenated decomposition furnace is used to liberate mercury from solid and aqueous samples in the instrument. The sample is dried and then thermally and chemically decomposed within the decomposition furnace. The decomposition products are carried by flowing oxygen to the catalytic section of the furnace. Oxidation is completed and halogens and nitrogen/sulfur oxides are trapped. The remaining decomposition products are then carried to an amalgamator that selectively traps mercury. After the system is flushed with oxygen to remove any remaining gases or decomposition products, the amalgamator is rapidly heated, releasing mercury vapor. Flowing oxygen carries the mercury vapor through absorbance cells positioned in the light path of a single wavelength atomic absorption spectrophotometer. Absorbance (peak height or peak area) is measured at 253.7 nm as a function of mercury concentration. The method can be used for individual species of mercury when an appropriate method or instrumentation has been used for separation (verification of acceptable method performance would be required if modifications are employed).

Total mercury (organic and inorganic) in soils, sediments, bottom deposits, and sludge-type materials as well as in aqueous wastes and ground waters can be determined without sample chemical pretreatment using this method, except as noted. Alternatively, this method can be used for the detection of total mercury from total decomposition sample preparation methods, such as Method 3052, or for detection of extracted or leached mercury compounds or species from methods such as the 3000 series methods (as detailed in Chapter Three).

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

Solvents, glassware, and other sample processing hardware can cause interferences if not free of contamination. Also, memory effects from analyzing a sample with higher mercury concentrations can carry over mercury interferences to a following sample with lower mercury concentrations. Groups of relatively higher and lower mercury-containing samples should be run together to minimize memory effects from carry over interferences.

QC Requirements:
For each batch of samples at least one method blank, one laboratory control sample (LCS), and a matrix spike / matrix spike duplicate (MS/MSD) must be run. See Chapter 1 for other QA/QC requirements.

Maximum Holding Time:
28 days



0.05 - 600 ng

Sample Prep:
See Chapter 3 as a reference.



Revision Number:
February 2007, Rev. 0