Frequent Questions

Is is mandatory to analyze a trip blank with a TTHM sample? Our lap gets several single sample work orders for TTHMs per day and the Trip Blanks add a lot of extra time.

With regard to analysis of trip blanks for samples analyzed using EPA Method 524.2, the method states in Section 9.7: “If a water sample is contaminated with an analyte, verify that it is not a sampling error by analyzing a field reagent blank” (aka trip blank). The method makes no provision to omit analysis of the trip blank if analyzing for disinfection by-products (THMs). The newer methods, 524.3 & 524.4, do make such an allowance. So the lab either runs 524.2 as written, or consider seeking certification for the newer method(s).

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