EPA Method 901.1

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EPA Method 901.1:
Gamma Radionuclides Screening. Official Name: Gamma Emitting Radionuclides in Drinking Water

A homogeneous aliquot of drinking water is put into a standard geometry for gamma counting. The counting efficiency for this geometry must have been determined with standard (known) radionuclide activity. Sample aliquots are counted long enough to meet the required sensitivity of measurement. The gamma spectrum is printed or stored for data processing and calculation of radionuclide concentrations in the sample.

Gamma spectroscopy for measuring gamma photons emitted from radionuclides without separating them from the sample matrix. This technique makes it possible to ascertain whether a hazardous concentration of a specific gamma emitter is present in drinking water samples.

Prescribed Procedures for Measurement of Radioactivity in Drinking Water (EPA/600/4-80-032), August, 1980.

Significant interference occurs when counting a sample with a NaI (Tl) detector and the sample radionuclides emit gamma photons of nearly identical energies. Such interference is greatly reduced by counting the sample with a Ge(Li) detector. Sample is important to gamma count reproducability and counting efficiency validity. When sample radionuclides are adsorbed on the walls of the counting container, the sample is no longer homogeneous. This problem can be lessened by adding 15 mL 1N nitric acid per liter of sample at collection time.

QC Requirements:
Calibration of instrument.

Maximum Holding Time:



60-2,000 keV

Sample Prep:


Detection level decreases with increased counting time.

Revision Number:

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Examples:  8260

Examples:  Dioxin
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