What is the suggested holding time for a sample before performing the SW-846 methods? What do I do if I hold it past the holding time?
The recommended holding time for a sample before performing any of the SW-846 methods depends on the specific constituents, matrix, and type of sample to be tested. Certain constituents in waste can degrade faster than others, such as volatile organic compounds. General guidelines for holding times are outlined in the appropriate tables of Chapters 2, 3 and 4 of SW-846 however, the selection of preservation techniques and applicable holding times should be based on all available information, including the properties of the analytes of interest for the project, their anticipated concentration levels, the composition of the sample matrix itself, and the stated project-specific Data Quality Objectives (DQOs). Many preparation and determinative methods provide more definitive guidance for holding times and supersede the general guidance provided in Chapters 2, 3, and 4.
An example of the impact of exceeding the holding time is shown for TCLP Method 1311. When sample holding times are exceeded, the TCLP analytical results will be considered the minimum amount that could leach from the waste. An identical sample analyzed from the same waste within hold time might yield higher concentrations of toxicity characteristic constituents. If a sample exceeds recommended holding time and analysis demonstrates that concentrations are above the regulatory threshold for one or more constituents, then these concentrations can be treated as minimum values and the waste is hazardous for the toxicity characteristic. No further testing is required. If, on the other hand, a sample exceeds a recommended holding time and analysis demonstrates that concentrations are below the regulatory threshold for one or more constituents, further testing will be necessary to demonstrate that the waste is nonhazardous.