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Preservation of Grabs and Comps
Keith C
Posted: Wednesday, June 13, 2012 12:49 PM
Joined: 6/13/2012
Posts: 4

The 2010 Method Update Rule, Table II, Note 2, requires that a grab be preserved within 15 minutes of being taken (except for metals samples).  It also requires that composites be preserved (if needed) within 15 minutes of the end of the composite period.  So, do I need to split out an aliquot from a comp for ammonia testing and preserve it within 15 minutes of the end of the 24 hour comp sampling period (which is from midnight to midnight for us) even though Standard Methods allows 24 hours before having to add the H2SO4 preservative?  Sure looks like I have to!
Posted: Friday, August 10, 2012 7:28 AM
Joined: 3/16/2012
Posts: 16

The way I read this note is that if the method does not discuss preservation, then  follow this criteria.  Note 2 states "except where noted in this TAble II and the method for the parameter.  The method we use states that samples are to be analyzed within 24 hrs or if held longer, then preserve.  I think you can make an argument that since the method allows 24 hr. holding before preservation, that this superceeds this note.