Method 9060A states, “In instances where analysis cannot be performed within 2 hr from time of sampling, the sample is acidified (pH < 2) with HCl or H2SO4.” However, our instrument manufacturer recommends using H3PO4 for preservation. Can H3PO4 be used for preservation for Method 9060A?
Method 9060A is on the list of method defined parameters (MDPs). Therefore, it must be followed exactly as written without deviation, even if substituting H2SO4 with H3PO4 is recommended by the instrument manufacturer. That being said, you can always seek permission for the substitution from your regulator or client. It will be rare that they grant permission, but depending on the circumstances for using the method, they may allow it. Be prepared to show equivalency data that the substitution works.
Other category: Holding Time & Preservation