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# Impurities Guide on Residual Solvents
- URL: https://www.fdaweb.com/impurities-guide-on-residual-solvents/
- Published: 2021-12-13T12:00:00.000Z
- Updated: 2026-09-14T17:25:35.000Z
- Author: David McFarland
- Tags: FDA Policy/General, #legacy-id-D5150756

*Federal Register* notice: FDA is making available a final guidance for industry entitled *Q3C (R8) Impurities: Guidance for Residual Solvents*. The International Council for Harmonization document provides recommendations for permitted daily exposures (PDEs) for three additional residual solvents: 2-methyltetrahydrofuran, cyclopentylmethyl ether, and tert-butyl alcohol. The agency says the PDEs were developed according to the methods for establishing exposure limits included in the guidance for industry *Q3C: Impurities Residual Solvents*. To view the notice, click [here](https://www.govinfo.gov/content/pkg/FR-2021-12-13/pdf/2021-26889.pdf?ref=fdaweb.com).