EPA-ORD / EPA-OST: 200.5: Trace elements in water by AVICP-AES
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Official Method Name
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Determination of trace elements in drinking water by axially viewed inductively coupled plasma-atomic emission spectrometry |
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Current Revision
| Rev. 4.2, October 2003 |
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Media
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WATER |
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Instrumentation
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Inductively Coupled Plasma - Atomic Emission Spectroscopy |
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Method Subcategory
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Inorganic |
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Method Source
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Citation
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Martin, T.D., 2003, Determination of trace elements in drinking water by axially viewed inductively coupled plasma-atomic emission spectrometry: U.S. Environmental Protection Agency Report EPA/600/R-06/115, Revision 4.2, 36 p. |
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Brief Method Summary
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This method provides a specific procedure utilizing axially-viewed plasma atomic emission signals generated only by pneumatic nebulization for the analysis of allanalytes.
A 50 mL aliquot of a well-mixed, non-filtered, acid preserved aqueous sample is accurately transferred to a clean 50-mL plastic disposable digestion tube containing a mixture of nitric and hydrochloric acids. The aliquot is heated to 95 deg C (+ or - 2 deg C), evaporated to approximately 25 mL, covered with a ribbed plastic watch glass and subjected to total recoverable solubilization with gentle refluxing for 30 minutes. The sample is allowed to cool and diluted to 25 mL with reagent water to effect a 2X preconcentration. The sample is capped, mixed and now ready for analysis (The time required to complete the sample preparation step is approximately 2.5 hours). The analytical determinative step described in this method involves multi-elemental determinations by AVICP-AES using sequential or simultaneous instruments. The instruments measure characteristic atomic-line emission spectra by optical spectrometry. Standard and sample solutions are nebulized by pneumatic nebulization and the resulting aerosol is transported by argon carrier-gas to the plasma torch. Element specific emission spectra are produced by a radio-frequency inductively coupled plasma. The spectra are dispersed by a grating spectrometer, and the intensities of the line spectra are monitored at specific wavelengths by a photosensitive device. Photo currents from the photosensitive device are processed and controlled by a computer system. A background correction technique is required to compensate for variable background contribution to the determination of the analytes. Background should be measured adjacent to the analyte wavelength during analysis. Possible interferences that can occur must be considered and are addressed appropriately in the method report. |
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Scope and Application
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This method is used to determine trace elements, as well as water matrix elements, in drinking water and drinking water supplies. Axially viewed inductively coupled plasma-atomic emission spectrometry(AVICP-AES) is used to determine trace elements, as well as water matrix elements, in drinking water and drinking water supplies. |
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Applicable Concentration Range
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Unless otherwise noted, the analytical range extends from the laboratory-determined MDL to the upper limit of the linear dynamic range. |
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Interferences
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Spectral interferences are caused by background emission from continuous or recombination phenomena, stray light from the line emission of high concentration elements, overlap of a spectral line from another element, or unresolved overlap of molecular band spectra. Physical interferences are effects associated with the sample nebulization and transport processes. Changes in viscosity and surface tension can cause significant inaccuracies, especially in samples containing high dissolved solids or high acid concentrations. Chemical interferences include molecular-compound formation, ionization effects, and solute-vaporization effects. In general, chemical interferences are highly dependent on matrix type and the specific element. Memory interferences result when analytes in a previous sample contribute to the signals measured in a new sample. Memory effects can result from sample deposition on the uptake tubing to the nebulizer and from the buildup of sample material in the plasma torch and spray chamber. |
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Quality Control Requirements
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Each laboratory using this method is required to operate a formal quality control (QC) program. The minimum requirements of this program consists of an 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. The laboratory is required to maintain performance records that define the quality of the data thus generated. |
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Sample Handling
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For the determination of trace and water matrix elements in drinking water and drinking water supplies, samples are not filtered, but acidified with (1+1) nitric acid to a pH < 2 (3 mL of [1+1] acid per liter of sample should be sufficient). Preservation may be done at the time of collection; however, to avoid the hazards of strong acids in the field, transport restrictions and possible contamination, it is recommended that the samples be returned to the laboratory within two weeks of collection and acid preserved upon receipt in the laboratory. Following acidification, the sample should be mixed, held for sixteen hours, and then verified to be pH < 2 just prior to withdrawing an aliquot for sample processing. If for some reason, such as high alkalinity, the sample pH is verified to be > 2, more acid must be added and the sample held for sixteen hours until verified to be pH < 2. |
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Maximum Holding Time
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Up to 6 months, if properly preserved |
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Relative Cost
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$201 to $400 |
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Sample Preparation Methods
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Method 200.2, Rev. 2.8 |
