EPA Method 200.12

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EPA Method 200.12:
Trace Elements in Marine Waters by GFAA. Official Name: Determination of Trace Elements in Marine Waters by Stabilized Temperature Graphite Furnace Atomic Absorption

Summary:
A sample is refluxed with nitric acid and then centrifuged or particulate is allowed to settle. An aliquot of treated sample is transferred to a stabilized temperature platform graphite furnace atomic absorption (STPGFAA) system. The aliquot is dried at a low temperature, charred/ashed to remove interferences, atomized, and concentrations of atomized elements are determined using a STPGFAA spectrophotometer.

Scope:
This method determines total recoverable elements in marine waters, including estuarine, ocean, and brines with salinites of up to 35 ppt.

Citation:
Methods for Determination of Chemical Substances in Marine and Estuarine Matrices - 2nd Edition (EPA/600/R-97/072)

Interferences:
(A) Blackbody radiation: Emission of blackbody radiation from the oven can interfere with absorbance measurements.(B) Elemental interferences: Spectral overlap of elemental absorptions can occur, but are relatively uncommon. Appropriate furnace temperature programs and high purity lamps can reduce interferences.(C) Molecular interferences: More common than elemental interferences, they can be reduced by using matrix modifiers, selective volatilization, background correctors, and appropriate furnace charring conditions. Note: The correct charring temperature is critical when analyzing saline waters.(D) Matrix interferences: Some matrix components can inhibit the formation of free atoms.(E) Memory interferences: Analyte can carry over in the furnace between runs. Use low concentration samples to ensure that analytes do not carry over.(F) Specific element interferences: Cadmium, selenium, and arsenic have characterized interferences and suggested interference removal procedures.

QC Requirements:
Initial demonstration of laboratory capability and the periodic analysis of laboratory reagent blanks, fortified blanks, and other laboratory solutions as a continuing check on performance.

Maximum Holding Time:
6 months.

Media:
WATER

Subcategory:
Inorganic

Concentration:
Not Provided

Precision:
Precision and accuracy values were calculated using data from 4 replicate analyses of a fortified certified seawater sample (NASS-3). Additional data are available in the method.

Detection:
MDL procedure is equivalent to the procedure at 40 CFR part 136, Appendix B. MDLs were determined using the standard deviation of 7 replicate analyses of a analyte-fortified reagent water sample multi

Revision Number:
Revision 1.0, September 1997