August 11, 2020

Analytical Sample Holding Time Guidance Incorporated Into SW–846

Analytical sample holding times are designed to minimize changes in the physical and chemical properties of a sample from the time it is collected until the time it is prepared and analyzed. Analysis of a sample after expiration of its recommended holding time may not accurately reflect the true nature of the analyte. RO 14933, published May 27, 2020 by EPA’s Office of Resource Conservation and Recovery (ORCR), provides guidance on recommended sample holding times included in SW–846 Chapters 3 and 4.

Chapter 3 of SW–846 contains guidance for the analysis of inorganic analytes in a variety of matrices. Chapter 4 of SW–846 contains similar guidance for organic analytes. The recommended holding times found within these chapters are considered guidelines and not EPA requirements. Consequently, there is no clear basis to distinguish between acceptable and unacceptable results if the analytical procedure was performed within a small interval of the recommended holding time. For example, should sample results be discarded if a sample was analyzed just hours after a 7-day holding time elapsed?

After review, ORCR provided the following guidance on sample holding times for the SW–846 program:

“Holding times for sample preparation and analysis greater than or equal to 7 days have been met if the sample is prepared or analyzed by the end of the last day or month of the specified maximum holding time. For example, a sample collected on a Tuesday is considered to have met a specified 7-day holding time as long as it is prepared or analyzed by the end of the day on the following Tuesday. A sample collected in January is considered to have met a specified 6-month holding time if it is prepared or analyzed before the end of July.”

This clarification will be incorporated into Chapters 3 and 4 of SW–846. ORCR noted that this interpretation is consistent with that described in the current Contract Laboratory Program’s National Functional Guidelines for Organic and Inorganic Superfund Methods Data Review and DOD/DOE Consolidated Quality Systems Manual for Environmental Laboratories.

While this interpretation and additional information found in Chapters 3 and 4 of SW–846 are EPA guidance, RCRA-authorized states can be more stringent when designating holding times or providing guidance on measuring holding times.


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