Granulation Loss on Drying (LOD)
Granulation loss-on-drying (LOD) measures the residual moisture in granules at end-of-drying — a CQA that decides whether the lot proceeds to milling, blending and compression or returns for additional drying.
01What LOD measures
LOD is the % weight loss when a sample is heated to a defined temperature for a defined time. The compendial reference is USP <731>; Karl Fischer (USP <921>) is the more specific water-only measurement. NIR moisture is increasingly used as PAT for continuous control. The end-of-drying LOD is the gate to release granules from the drier.
- Typical solid-dose LOD spec: 1.0–3.0% depending on product.
- LOD includes any volatile, not just water; KF measures water only.
- NIR moisture validated under ICH Q2/Q14 can replace destructive sampling.
- Water activity (USP <1112>) supplements LOD for microbial-risk decisions.
02Methods compared
| Method | Strengths | Weaknesses |
|---|---|---|
| IR-balance LOD | Fast, on-floor | Measures all volatiles, not just water |
| Oven LOD (USP <731>) | Compendial reference | Slow |
| Karl Fischer (USP <921>) | Water-specific, precise | Lab method, slow |
| NIR moisture (PAT) | Real-time, non-destructive | Requires Q2/Q14 method |
| Water activity (aw) | Microbial risk indicator | Not a moisture % |
03Execution and controls
- Sample at end-of-drying from multiple bed locations (stratified).
- Use the validated method — don't switch IR for oven mid-campaign.
- Bridge NIR to KF during PPQ for the regulatory record.
- Tie LOD spec to dissolution and stability data — not picked from thin air.
- Record LOD in the batch record as a CQA, not just an in-process flag.
04Common mistakes
- Sampling only the top of the bed — bottom may still be wet.
- Using IR for batch release without bridge to compendial method.
- Specs copied from a similar product without dissolution justification.
- No NIR/PAT trending — drying time creep across campaign goes unnoticed.
- Treating LOD pass as moisture pass — volatile residual solvents missed.
05Cross-industry examples
- Solid-dose pharma — LOD spec is standard release attribute.
- Nutraceutical chewables — moisture drives shelf-life and microbial limit.
- Effervescent — extremely low LOD (<0.5%) needed.
- Veterinary medicated articles — LOD ties to active stability.
- Food/instant powders — moisture drives flow, caking and microbial limits.
06How V5 Ultimate handles LOD
Frequently asked questions
Q.IR balance acceptable for release?+
Usually yes once bridged to compendial method during validation; some sites require KF for final release.
Q.What if LOD is high?+
Return to drier for additional time within validated parameters; re-test.
Q.What if LOD is too low?+
Some products specify a lower limit too — too-dry granules cap on the press. Investigation may be required.
Q.Can NIR replace destructive sampling?+
Yes once Q2/Q14 validated. Most sites run both at PPQ and reduce to NIR-primary in CPV.
Q.Is water activity needed?+
For microbial-risk products yes (USP <1112>); for chemistry-only LOD usually sufficient.
Primary sources
Further reading
V5 Ultimate ships with the Granulation Loss on Drying (LOD) controls already wired in — audit trail, e-signatures, validation evidence. Free trial, no credit card, onboard in days, not months.