Standard Methods: 7500-Ra B: Radium by Precipitation

Summary
Analytes
Revisions
Data and Sites

Official Method Name

7500-Ra B. Precipitation Method

Current Revision

Standard Methods Online

Media

WATER

Instrumentation

Alpha Scintillation

Method Subcategory

Radiochemical

Method Source

Standard Methods

Citation

Standard Methods Online - Standard Methods for the Examination of Water and Wastewater

Brief Method Summary

Because of the difference in half-lives of the nuclides in the series including the alpha-emitting Ra isotopes, these isotopes can be identified by the rate of ingrowth and decay of their daughters in a barium sulfate precipitate. Lead and barium carriers are added to the sample containing alkaline citrate, then sulfuric acid (H₂SO₄) is added to precipitate radium, barium, and lead as sulfates. The precipitate is purified by washing with nitric acid (HNO₃), dissolving in alkaline EDTA, and reprecipitating as radium-barium sulfate after pH adjustment to 4.5. This slightly acidic EDTA keeps other naturally occurring alpha-emitters and the lead carrier in solution.

Scope and Application

This method is suitable for determination of the alpha-emitting isotopes of radium. The determination of radium by precipitation includes all alpha-emitting radium isotopes; it is a screening technique particularly applicable to drinking water. As long as the concentration of radium is less than the ²²⁶Ra plus ²²⁸Ra drinking water standard, examination by a more specific method is seldom needed. This method also is applicable to sewage and industrial wastes, provided that steps are taken to destroy organic matter and eliminate other interfering ions.

Applicable Concentration Range

Interferences

Quality Control Requirements

See Section 7020 Quality Assurance/Quality Control.

Sample Handling

Plastic or glass containers. Preserve with concentrated HCl or HNO3 to pH <2.

Maximum Holding Time

1 year

Relative Cost

Greater than $400

Sample Preparation Methods

This method has 1 analyte associated with it.

Analyte	Detection Level	Bias	Precision	Pct False Positive	Pct False Negative	Spiking Level
Radium(7440-14-4) Ra Radium	N/A	98% Rec (ML)	N/A

Precision Descriptor Notes:	In a collaborative study, 20 laboratories analyzed four water samples for total (dissolved) radium. The radionuclide composition of these reference samples is shown in a table in the method. The average recoveries of radium-226 from the remaining A, B, C, and D samples were 97.5, 98.7, 94.9, and 99.4%, respectively. At the 95% confidence level, the precision (random error) was 28% and 30% for the two sets of paired samples.
Detection Level Note:

Precision Descriptor Notes:

In a collaborative study, 20 laboratories analyzed four water samples for total (dissolved) radium. The radionuclide composition of these reference samples is shown in a table in the method. The average recoveries of radium-226 from the remaining A, B, C, and D samples were 97.5, 98.7, 94.9, and 99.4%, respectively. At the 95% confidence level, the precision (random error) was 28% and 30% for the two sets of paired samples.

Detection Level Note:

Revision	PDF/Link
Standard Methods Online
Standard Methods 18th, 19th, 20th ed.

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Standard Methods: 7500-Ra B: Radium by Precipitation

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