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7 SAMPLE ANALYSIS TOOLS for METALS

7.1 EX-SITU ANALYSIS

7.1.1 Atomic Absorption (AA) Spectroscopy

Use: Analyzing heavy metals.

Description:

Atomic absorption (AA) spectroscopy involves the absorption of radiant energy by neutral atoms in the gaseous state. Since samples are usually liquids or solids, the analyte atoms or ions must be vaporized in a flame or graphite furnace. The atoms absorb ultraviolet or visible light and make transitions to higher electronic energy levels. The analyte concentration is determined from the amount of absorption.

All AA spectroscopy instruments have the following basic features:

  1. Light/radiant energy source that emits resonance line radiation.
  2. Sample chamber where sample is fed as an aerosol and vaporized. Samples are generally vaporized either by a flame (aerosol mixed with fuel and oxidant gas) or furnace.
  3. Device for selecting only one of the characteristic wavelengths (visible or ultraviolet) of the element being determined.
  4. Detector, generally a photomultiplier tube (light detectors that are useful in low intensity applications), which measures the amount of absorption.
  5. Readout system (strip chart recorder, digital display, meter, or printer).

More sophisticated instruments can have more than one channel for simultaneous determination of more than one element. Multi-element sequential instruments can be programmed to automatically determine chosen elements sequentially.

Analytes:

7. Metals

Media:

Soil/Sediment Water Gas/Air
Requires extraction to liquid phase Requires extraction BETTER
Selectivity: Technique measures the contaminant directly.
Susceptibility to Interference: Low.
Detection Limits : 100-1000 ppb (soil); 1-50 ppb (water).
Turnaround Time per Sample: More than a day.
Applicable To:
Screen/Identify Characterize Concentration/Extent Cleanup Performance Long-Term Monitoring
SERVICEABLE BETTER SERVICEABLE ADEQUATE
Quantitative Data Capability: Produces quantitative data.
Technology Status: Commercially available technology with limited field experience.
Certification/Verification: Technology has not participated in CalEPA certification and/or CSCT verification program.
Relative Cost per Analysis: Most expensive if many elements are in the sample.

Limitations:

ASTM Standards:

E 1727 - 95 Field Collection of Soil Samples for Lead Determination by Atomic Spectrometry Techniques.

EPA Methods:

7000A Atomic Absorption Methods (RCRA).
Series 7000 47 Methods for Specific Analytes.
200.0 Atomic Absorption Methods (Drinking Water).
Series 200 63 Methods for Specific Analytes and Techniques.
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