NJDEP-SRP Low Level TO-15 Series: Part 5 – Method detection limits…

If you recall from part 1 of this blog series, NJ LL TO-15 listed MDLs as being one of the items they modified from U.S. EPA Method TO-15. HOWEVER, the only “modification” I see made is that NJ LL has outlined “specific criteria that the laboratory must meet regarding the MDL and an MDL study must be conducted annually.” Other than that, NJ LL TO-15 actually states that “the laboratory shall calculate all Method Detection Limits (MDLs) in accordance Method TO-15. Section 11.2 of US EPA Method TO-15 requires the use of the procedures stated in Appendix B of 40 CFR 136 for performing the MDL study.”

So what does this mean? It means that we are basically doing what we always do for U.S. EPA Method TO-15, with the stipulation that we must conduct our MDL determination using a spiking solution at 0.20 ppbv and the derived MDL must be less than the Clean Canister Certification Level of… you guessed it… 0.20 ppbv. NJ LL does allow for some compounds to be spiked at higher concentrations, but we are going to skip over this cop-out, because we can get it done with the 0.2 ppbv. So using the parameters outlined in blog parts 2 and 3 of this series, we fire off 7 injections of our 0.2 ppbv standard onto the Markes CIA Advantage and here is what we get:

Everything passes with flying colors! Yes, acetone and TBA were above 0.20 ppbv (marginally), but NJ LL already accounted for this and gave us some leeway by setting higher MDLs for acetone (1.00 ppbv) and TBA (3.00 ppbv). Remember that this is all done with full scan and only a 250 mL injection. Oh, and as usual these results were obtained on the same dirty source and without manual integrations (i.e., these are realistic results you should be able to easily achieve). Stay tuned for the final blog on NJ LL TO-15...