22.214.171.124 Sample processing
Two key issues are the applicability of air-drying and the use of particle size reduction to facilitate representative laboratory subsampling. These techniques generally work well for higher-boiling-point, thermally stable contaminants. The question of whether to grind samples prior to metals analysis should be carefully considered, since this can both improve reproducibility and release metals previously bound inside particles that were less environmentally accessible. The ISM principles have been applied to VOCs in a manner that does not require air-drying or additional air exposure. See Section 5 for field activities and Section 6 for the corresponding laboratory activities.
Meeting traditional holding times is more challenging when air-drying and particle size reduction techniques are used at the laboratory, due to the lengthened sample processing; however, data from USEPA SW-846 Method 8330B studies indicate that contaminant stability can be much longer in dried samples than is common in as-received moist samples. The Method 8830B process has been validated for energetic residues, but it should not be assumed to apply to all other contaminants or contaminant groups. See Section 6.2 for a detailed discussion of the strengths and limitations of the various ISM sample processing options.
Lab certification for ISM sample processing procedures may require certification by laboratory SOP except for USEPA SW-846 Method 8330B. This may be a significant limitation for certain regulatory entities. Please see Section 6.4 for more details.
Below is a list of recommendations for addressing matrix and parameter issues:
- Minimize error by processing ISM samples in a controlled setting.
- Do not use particle size reduction on ISM samples to be analyzed for organic contaminants other than energetics.
- Request that the lab analyze a laboratory control sample at a minimum frequency of one per analytical batch of 20 ISM samples.
- When analyzing ISM samples for SVOCs, confirm that drying is acceptable for the specific target compounds.