Description:
Holding times are the length of time a sample can be stored after collection and prior to analysis without significantly affecting the analytical results. Holding times vary with the analyte, sample matrix, and analytical methodology used to quantify the analytes concentration. Maximum holding times (MHTs) have been established by the U.S. Environmental Protection Agency (EPA) and have been presented in the Code of Federal Regulations (CFR) and SW-846 methods manual. Holding times can be extended if preservation techniques are employed to reduce biodegradation, volatilization, oxidation, sorption, precipitation, and other physical and chemical processes. Under this task, samples will be collected, held, and analyzed after specific time periods (fractions or multiples of the MHTs) to determine the validity of the existing current holding times. Matrices to be examined are soils and sediments. Analytes to be examined include heavy metals, Cr(VI), pesticides, PAHs, and PCBs.
This work is part of the Regional Methods Initiative (RMI) program in ORD. The work has been initiated at the request of and in collaboration with two EPA Regions - I and X.
Keywords:
HOLDING TIMES, SAMPLE PRESERVATION, SAMPLE STABILITY, SAMPLE HANDLING, PCBS, PESTICIDES, PAHS, SOIL, WATER, SEDIMENT, REGIONAL METHODS INITIATIVE, RMI,
Project Information:
Progress
:All laboratory analyses have been completed. Statistical interpretations are underway. The report and subsequent journal articles are anticipated to be completed by January, 2005.
*** see attached interim reports for more complete status ***
Relevance
:The research to be conducted under this task is in direct response to two Regional Methods Initiatives requests; one from U.S. EPA Region I and the other from Region X.
Holding times are the length of time a sample can be stored after collection and prior to analysis without significantly affecting the analytical results. Holding times vary with the analyte, sample matrix, and analytical methodology used to quantify the analytes concentration. Maximum holding times (MHTs) have been established by the U.S. Environmental Protection Agency (EPA) and have been presented in the Code of Federal Regulations (CFR) and SW-846 methods manual. Holding times can be extended if preservation techniques are employed to reduce biodegradation, volatilization, oxidation, sorption, precipitation, and other physical and chemical processes.
While holding times may appear adequate to protect sample integrity and provide sufficient time for laboratory analysis, relevant data is sparse on individually defined holding times and, thus, some of the holding times appear to be arbitrary and/or politically driven. Holding times appear to be arbitrary when a single value is applied over a large general class of compounds (e.g., pesticides or polyaromatic hydrocarbons); when the holding time was originally "established" for aqueous media and then blindly applied to other media (e.g., sediments and tissues); or when a contaminant is known to be chemically highly stable and will still be present in the sample even if the sample is not extracted in the regulatory time frame. For example, if PCBs significantly degraded after 7 days, then there would not be an environmental problem with PCBs today.
Holding times may appear politically driven to speed commercial laboratories in sample analysis and report production. While holding times tend not to be a major concern for large commercial laboratories, they may be especially harmful for non-production-based analytical laboratories, such as EPA Regional laboratories. The primary concern of both government and private laboratories occurs when their sample load is heavy or excessive, instruments break down, or extraction difficulties occur due to matrix complications and the holding times are, thus, exceeded. If the holding times are exceeded, even if only by 1 day, the data must be flagged and is often declared invalid or are reported as "estimated", and the data are then called into question, especially if the data are to be used in a court of law. Once declared invalid, the time and expense associated with the sample collection and processing is forfeited even though, in truth, the analytical result may be perfectly accurate (i.e., sample integrity is maintained). The potential for missing holding times often causes a laboratory to charge extraordinary fees to pay for overtime, or in many cases, to simply turn away work for fear of having data rejected should it not meet the arbitrary holding times. From the Agency's point of view, holding times are particularly objectionable when they cause data to be rejected, delay projects, and cost the government money for rework that is unnecessary.
The results from this study will be used by the Regions and Program Offices to assess the validity of currently recognized holding times in 40 CFR and will provide a scientific basis for changes that may be necessary to the current regulations.
Clients
:Robert Maxfield, EPA Region I, Gerald Dodo, EPA Region 10, Roseanne Lorenzano, EPA Region 10, David Friedman, OAA, Sharon Frey, OERR; Jan Young, OERR
Project IDs:
ID Code
:9521
Project type
:OMIS