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SolventSelector

ICH calculator — methodology & limits

Last reviewed July 2026.

⚠ Reference & education only — not for regulatory submission

This tool computes acceptance limits from published PDE values using the standard ICH formulas. It is not a substitute for the current ICH guidelines, USP chapters, or your own qualified analysis. Always verify limits against the current primary source before using them in a regulatory filing or release decision.

The formulas

Q3C (residual solvents): concentration limit (ppm) = 1000 × PDE (mg/day) ÷ daily dose (g/day). Option 1 uses a 10 g/day dose assumption; Option 2 uses the actual dose.

Q3D (elemental impurities): concentration limit (ppm = µg/g) = route PDE (µg/day) ÷ daily dose (g/day), using the oral, parenteral, or inhalation PDE.

Sources

  • ICH Q3C(R9) — Impurities: Guideline for Residual Solvents (class assignments, PDEs, Option 1 concentration limits).
  • ICH Q3D(R2) — Guideline for Elemental Impurities (PDEs by route).
  • USP General Chapters — <467> Residual Solvents and <232>/<233> Elemental Impurities.

How the values are verified

The PDE and limit values are compiled from the ICH guidelines and cross-checked against the corresponding USP chapters via an adversarial verification pass (each value re-checked against a second authoritative source). Any value with residual uncertainty is flagged. This is a v1 dataset; a pharmaceutical professional should confirm critical values against the current guideline before use.

Found a value that looks off? Email [email protected] — corrections are welcome.