Is it permissible to use a reduced sample volume (e.g., 50g/1L extraction fluid vs. 100g/2L) to perform the leachate extraction as long as the 20:1 extraction fluid to dry weight ratio is maintained?
Since Method 1311 is a Method Defined Parameter (MDP) method, it is exempt from the flexibility clause that is in effect for most of the other SW-846 methods. As such, it must be followed prescriptively, especially in a regulatory situation.
There are multiple places within the method that call for a minimum of 100-gram samples. When the method indicates a 100-gram minimum is recommended, it means that a larger sample size may be needed with some types of wastes, especially if it is very heterogeneous. Concrete is a good example of heterogeneous waste. If more than the minimum of 100-grams is used, you must retain the 1:20 ratio of solids to fluid. The method warns samplers to make sure enough sample is provided for the correct weight of sample required, plus extra for the duplicates and the preliminary tests for particle sizing and fluid selection.
If you are doing organic volatiles you must use the zero-headspace extractor (ZHE) and the minimum sample size is reduced to 25 g due to the 0.5-L volume limitation of the ZHE device. For all other extractions not done in a ZHE, the minimum is 100 g. If you use less than 100 g, even if you use the correct solid:fluid ratio, the results will not be valid.