What are the guidelines for the hydrolysis step in 8151A for environmental samples? Shouldn't hydrolysis always be performed?
Most chlorinated herbicides in the 8151A list come in numerous formulations including acids, esters, and salts. The purpose of the hydrolysis step in method 8151A is to convert all of the ester herbicides into acid form. While the esters have a half-life of about a week in soil matrices, they are stable enough to be detected by the method when the hydrolysis step is performed. Therefore, not performing the hydrolysis step would not detect fresh applications of ester formulations. Given that it seems to be a relatively rare situation when esters are not required analytes, it seems most practical to always perform the hydrolysis step.