In Hach Method 10263, why is hydrochloric acid added to the standard in the accuracy check step but not to a sample?

Document ID

Document ID TE1342

Published Date

Published Date 12/03/2017
Question
In Hach Method 10263, why is hydrochloric acid added to the standard in the accuracy check step but not to a sample?
Summary
Method 10263 hydrochloric acid added to standard
Answer
The FerroZine® added right to the sample complexes the iron so it does not stick to the walls of the glass. In the accuracy the addition of acid prevents the iron in the standard from sticking to the glass prior to adding FerroZine®.