TM23-02 Discontinuation of surrogate compound tetrahydrofuran-d8 and addition of surrogate compound 1,3-dioxane to National Water Quality Laboratory schedules 4437 and 4447 that use Method O-4437-16

This memorandum alerts users of the U.S. Geological Survey (USGS) National Water Quality Laboratory (NWQL) of a modification to USGS Method O-4437-16: Determination of heat purgeable and ambient purgeable volatile organic compounds in water by gas chromatography/ mass spectrometry [GC/MS] (Rose and others, 2016). Surrogate compound 1,3-dioxane, National Water Information System (NWIS; https://waterdata.usgs.gov/nwis) parameter code 90870, will replace surrogate compound tetrahydrofuran-d8, parameter code 90607. This modification is relevant to samples analyzed by NWQL schedules 4437 and 4447 (NWIS method code GM016 for both schedules) and will be implemented on October 1, 2023.