As-Is vs Anhydrous Basis
As-is, anhydrous and anhydrous-and-solvent-free are the three common bases on which assay, potency and recipe targets can be expressed. Choosing — and declaring — the basis is the single most consequential decision in a manufacturing recipe: get it wrong and every dispense across every campaign over-charges or under-charges silently. ICH Q6A and USP General Notices 6.30 formalise the choice; every well-run dispensing engine enforces it.
01Definitions
- As-is basis — the assay or content is reported per the material as it physically exists, including any water and residual solvent.
- Anhydrous basis — the assay is computed after mathematically subtracting the water content; the same lot reports differently on as-is vs anhydrous bases by exactly the water content.
- Anhydrous-and-solvent-free basis — also subtracts residual organic solvents; common for APIs and reference standards.
- Dried basis — the assay applies after a defined drying procedure (e.g. 105°C, 3 h) and is functionally similar to anhydrous when the volatile loss is essentially water.
02Why the basis matters
Consider a lot with 99.4% assay on anhydrous basis and 2% water. On an as-is basis the assay is 99.4 × 0.98 = 97.4%. A recipe targeting '10.000 kg API' must either (a) declare it means 10.000 kg anhydrous → dispense 10.265 kg as-is, or (b) declare it means 10.000 kg as-is → dispense 10.000 kg of as-is mass. The two answers differ by 2.65%. Mis-declaration over a campaign creates systematic mis-dosing that QC may detect (impurity, content uniformity) or may not detect for months.
03Where the basis lives
| Object | Basis declaration |
|---|---|
| Material master | Default basis for recipe targets and lot attributes for this material |
| Material spec | Acceptance limits each on an explicit basis |
| Recipe target | Recipe-level explicit basis (may override material default) |
| Lot assay attribute | Per-lot value on an explicit basis (must match the lot's measurement method) |
| CoA from supplier | Each value on its own basis; receive-time parsing must capture the basis |
| Reference standard | Potency typically reported on anhydrous-and-solvent-free basis |
04Switching between bases
Conversions are mechanical when the underlying measurements are present:
- Anhydrous → as-is: A_as-is = A_anh × (100 − Water%) / 100.
- As-is → anhydrous: A_anh = A_as-is × 100 / (100 − Water%).
- Anhydrous → anhydrous-and-solvent-free: A_asf = A_anh × 100 / (100 − Residual solvents%).
- Dried (defined method) ≈ anhydrous if drying conditions volatilise only water; otherwise treat as a distinct basis.
05Common mistakes
- Recipe target labelled 'mg API' without specifying basis — every dispense is a coin flip.
- Supplier CoA reports anhydrous assay; in-house assay reports as-is; both stored together without basis tag.
- Dried-basis used as a synonym for anhydrous when LOD includes non-water volatiles.
- Reference standard potency converted from anhydrous-and-solvent-free to anhydrous without accounting for solvents.
- Operator screen shows a single 'assay' value without the basis — manual decisions made under ambiguity.
- Conversion done in spreadsheets outside the validated system — auditor cannot reconstruct.
06Cross-industry examples
- Pharma APIs — anhydrous-and-solvent-free is the convention for the assay; recipe targets typically anhydrous with explicit moisture correction at dispense.
- Excipients (lactose monohydrate) — as-is is normal because the monohydrate is the supplied form; switching to anhydrous misrepresents the carrier.
- Biopharma reference standards — anhydrous-and-solvent-free with declared certified potency.
- Food ingredients — varies by category; oils on as-is, dry ingredients on a defined dried basis.
- Cannabis — cannabinoid potency reported on dry basis per state-regulator rules; biomass moisture corrected at use.
- Animal feed premixes — vitamin potency on as-is unless premix supplier specifies otherwise.
07How V5 Ultimate handles basis declarations
Frequently asked questions
Q.Which basis should we standardise on?+
Anhydrous (or anhydrous-and-solvent-free) is the cleanest convention for actives because it isolates the active mass from variable solvent/water content. Excipients often stay as-is when the supplied form (e.g. monohydrate) is intentional. Whichever you choose, declare it explicitly everywhere.
Q.Can recipe targets and assay attributes be on different bases?+
Yes, provided the conversion attributes (water, residual solvents) are present so the engine can compose the correction. The eBR must record the conversion explicitly.
Q.How do we handle USP/Ph. Eur. monograph assays that specify a basis?+
Use the monograph basis as canonical for the material; recipe targets either match it or are on a different basis with explicit conversion. Do not silently re-base a monograph value.
Q.What about hydrates like lactose monohydrate or trihydrates?+
The supplied form IS the material; basis is as-is. Charging on anhydrous would imply you intend to dry the carrier, which is rarely the case. The material master must reflect the supplied form.
Q.How do we audit historical batches when the basis was ambiguous?+
If the basis was not captured in the eBR, the historical dispense is open to question. Best practice going forward: backfill the basis on materials in current use, document any ambiguous historical batches, and assess the impact on released product if the ambiguity affects content uniformity or impurity profile.
Primary sources
Further reading
V5 Ultimate ships with the As-Is vs Anhydrous Basis controls already wired in — audit trail, e-signatures, validation evidence. Free trial, no credit card, onboard in days, not months.