Analysis

Reliable analytical measurements of environmental samples are the next essential ingredient, after sampling, in making sound decisions about safeguarding public health and improving the quality of the environment.

Analytical Methods

The development of analytical methods bgan in the late 1800s to support water purification, commerce and agriculture. Today, the EPA provides the analytical methods for compounds of interest under the different regulations.

  • List of Lists-A Catalogue of Analytes and Methods, US EPA Office of Water
  • Methods for Chemical Analysis of Water and Wastes, EPA-600/4-79-020
  • Test Methodds for Evaluating Solid Waste, 3rd edition, SW-846
  • Contract Laboratory Program (CLP) Methods

Common Analyses

Spectrophotometry: Adsorption spectrophotometry measures the interaction of electromagnetic radiation with matter. Often used for drinking water and wastewater.

Electrode Methods: The determination of Ph and fluoride are examples of electrode methods. The potential (voltage) from an electrode sensitive to the material of interest is measured against a standard potential. Often used for drinking water and wastewater.

Gravimetric Methods: Examples of gravimetric analyses are the Total Residue Method and the Oil and Grease Method. Gravimetric methods require weighing small amounts of the material of interest on a sensitive laboratory balance. Often used for drinking water and wastewater.

Titrimetric Methods: Titrimetric methods of analysis require dispensing accurately measured volumes of reagents of known concentration. At the "end point" of a titrimentric analysis, the added reagent exactly balances the concentration of the material of interest. Often used for drinking water and wastewater.

Gas Chromatography: Volatile compounds may be gases at standard conditions or liquids or solids that can be converted to vapor by heat. Environmental samples of water, soil, or waste can be sampled with gas chromatography. Gas chromatography provides a pictorial record of the separated sample components. Results are both qualitative (what is present) as well as quantitative (how much is present). Often used for volatile compounds.

Mass Spectrometry: An analytical technique used for to identifiy and quanitfy compounds. This technique can also be used to determine the molecualr structure of the compound. A mass spectrometer is used to produce ions from from the compound which are then seperated according to their charge-to-mass ratios (m/z, or mass/intensity)

Liquid Chromatography: A technique for seperating a mixture of components. The technique involves two phases: a liquid mobile phase and a stationary phase, usually a solid. The components of the liquid pass through the solid at different speeds and, thus, are seperated.

Units of Measure

Measurements are obtained from anlaytical laboratories and from field instruments. Common examples for chemical concentrations are listed below:

  • mg/m3 (milligrams per cubic meter) used for gas vapor in air, lead dust in air

  • mg/kg (milligrams per kilogram) used for solids. Also known as ppm or parts per million
  • micrograms/cm2 (micrograms per square centimeters) used for measure of quantity of a substance present on a specific surface area.
  • mg/L (milligrams per liter) used for contaminants such as pesticides, organics and heavy metals in water or other liquids
  • f/cc (fibers per cubic centimeter) used for asbestos and other fibers
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