Frequent Questions

Use of Sulfuric Acid Cleanup vs. DDT analog standard for SW-846 Method 8082A.

Our lab does analysis of Polychlorinated Biphenyls (PCBs) as Aroclors by 8082A and uses Sulfuric Acid Cleanup 3665 for all extracts. We were recently audited and got a finding for not running the DDT analog standard.  We use pattern recognition for confirmation.

Will the sulfuric acid cleanup remove the DDT?

Is there still a need to run the DDT analog standard?

 

Method 8082A is meant for guidance only and can be modified according to the Method Innovation Rule (MIR) adopted by SW‐846 in 2005.  However, if any modifications are made, the laboratory has to demonstrate equivalency to the satisfaction of the client/auditor/regulator.  

Section 11.5 of Method 8082A states: "When conducting either Aroclor or congener analysis, it is important to determine that common single-component pesticides such as DDT, DDD, and DDE do not elute at the same retention times as the target congeners."  

It is likely that your auditor considers the use of a stronger word "important" over "recommended" (for example) to be analogous to the use of "must" over "should".   "Important" implies the determination stated in Section 11.5 is a requirement.  Running the DDT analog standard needs only to be done in conjunction with retention time window studies and may provide some valuable information in the event that you analyze a sample that contains the pesticides.

There is no guarantee the sulfuric acid clean‐up will remove all of the DDT, DDE, DDD, etc.  However, the laboratory could perform studies to determine the effectiveness of the cleanup on specific samples.  Extending the results of that study to any and all possibilities may be difficult and will most likely require a level of effort well in excess of that required to run the standard as described in the method.

 

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