And does anyone have a vetted spreadsheet or script for the 2017 rev. 2 MDL procedure (seven spikes over at least three days, MDLb included, 99% t-stat) that has passed NELAP or state audits? This is for ICP-MS trace metals in surface water under NPDES reporting and EIA screening, so I need a defensible path from raw data to MRLs/reporting limits.
I’ve got a locked Google Sheet that passed NELAP for ICP‑MS last year; the one thing that saved us was using a one‑sided 99% t‑stat (Excel T.INV(0.99, n‑1)) and hard‑requiring three unique prep dates before it calculates MDL = max(MDLsp, MDLb). > EIA screening, so I need a defensible path from raw data to MRLs/reporting limits. Ours logs raw intensities/dilutions and cites 40 CFR 136 App B: eCFR :: Appendix B to Part 136, Title 40 -- Definition and Procedure for the Determination of the Method Detection Limit—Revision 2 — want a copy?
For a solid approach, I’d recommend using a spreadsheet with embedded formulas for your MDL calculations — it’s a bit like building a house: a sturdy foundation makes for easier walls. If you’d like, I can share a template to help you get started; just let me know.
Having a vetted spreadsheet is crucial for NPDES reporting, especially with that 2017 rev. 2 MDL procedure. I used a customized approach with Excel that not only streamlined the MDL calculations but also incorporated LODs without much hassle.