Is there a reference by EPA or others that addresses that no more than either 1% or 10% of a chemical preservative should be used when sampling liquid media?
There is no known reference that specifically addresses that issue or sets a limit. There are so many preservation situations, depending on the analyte, the method, and the sample matrix, it would be difficult to make a general statement that would be valid for every case or even many cases. There may be cases where more than 10% of a preservative by volume may be needed to reach a particular state. For example, alkaline wastes may need more than 10% by volume of acid to reach a desired pH for metals preservation.
However, in all situations, good laboratory practices should be followed to record the actual amount, type, and concentration of preservative used in any study. That way, dilutions due to preservative can be corrected, and method blanks can be prepared with the same amount of preservative. The data quality objectives (DQOs) of the study at hand will dictate whether the dilutions need to be corrected or if the dilutions due to preservative addition can be ignored.