What is the purpose of a Method Blank?

A method blank (MB) is an analyte-free matrix such as DI Water for liquids or cleaned sand for solids and/or soils that is processed in exactly the same manner as the samples. The main function of the MB is to document contamination resulting from the analytical process. For an MB to be acceptable it must be no higher than the highest of the following:

–The method detection limit (MDL)
–5% of the regulatory limit of the analyte being tested
–5% of the measured concentration in the sample

The importance of the method blank is the confidence it provides in assuring the reported values found in your samples are “real” and not the result of laboratory contamination.