EPA Method 1639


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EPA Method 1639:
Trace Elements in Water by GFAA. Official Name: Determination of Trace Elements in Ambient Waters by Stabilized Temperature Graphite Furnace Atomic Absorption

Summary:
An aliquot of a well-mixed, homogeneous aqueous sample is accurately measured for sample processing.For total recoverable analysis of an aqueous sample containing undissolved material, analytes are first solubilized by gentle refluxing with nitric and hydrochloric acids. After cooling, the sample is made up to volume, mixed, and centrifuged or allowed to settle overnight prior to analysis.To determine dissolved analytes in a filtered aqueous sample aliquot, the sample is made ready for analysis by the appropriate addition of nitric acid, and then diluted to a predetermined volume and mixed before analysis.The analytes are determined by stabilized temperature platform graphite furnace atomic absorption (STPGFAA).

Scope:
This method determines dissolved and total recoverable elements at EPA water quality criteria (WQC)levels in ambient waters.

Citation:
EPA Method Guidance CD-ROM (includes MCAWW Methods, and most current EPA Methods)

Interferences:
(1) Contamination: Potential sources of trace metals contamination during sampling include metallic or metal-containing labware (e.g., talc gloves that contain high levels of zinc), containers, sampling equipment, reagents, and reagent water; improperly cleaned and stored equipment, labware, and reagents; and atmospheric inputs such as dirt and dust. Even human contact can be a source of trace metals contamination. For example, it has been demonstrated that dental work (e.g., mercury amalgam fillings) in the mouths of laboratory personnel can contaminate samples that are directly exposed to exhalation. The method provides numerous contamination control measures(2) Spectral interferences (elemental): Elemental interferences are caused by an overlap of elemental wavelengths. This does not normally occur.(3) Specrtal interferences (molecular): Molecular interferences are more common than elemental because of the broadband absorption of molecules over 100s of nanometers. This interference can be minimized or eliminated by use of matrix modifiers, selective volitalization, and background correction.(4) Spectral interference (black body emission): Spectral interferences can be cause by the emissions from black body radiation produced during the atomization furnace cycle. Appropriate alignment of the furnace tube and monochromator, along with appropriate volitalization temperatures can reduce this interference.(5) Matrix interferences caused by sample components that inhibit the formation of free atomic analyte atoms during the atomization cycle. Matrix interferences can be chemical or physical. Specific element interferences for antimony, cadmium, and selenium (as well as remedies) are discussed in the method.(6) Memory interferences: Carryover between sample runs can lead to artifacts in analyses. Chances of errors from memory interferences can be reduced by running blanks (to test for effects) and diluting samples.

QC Requirements:
QC elements include a calibration blank (CB), laboratory blank (LB), reagent blank (RB), field blank (FB), equipment blank (EB), quality control sample (QCS), ongoing precision and recovery (OPR), calibration verification (CV), matrix spike (MS), matrix spike duplicate (MSD), initial precision and recovery (IPR), method detection limit (MDL), and linear dynamic range (LDR) samples.

Maximum Holding Time:
6 months.

Media:
WATER

Subcategory:
Inorganic

Concentration:
Varies with analyte.

Precision:
-

Detection:
(1) Method Detection Limit (MDL) as determined by 40 CFR part 136, Appendix B. (2) The MDLs were determined in a three-laboratory validation study for elements in the method, except trivalent chromium.

Revision Number:
Jan-96

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Examples:  8260
TO-15

Examples:  Dioxin
Mercury
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