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Key: test item, instrument name, total nonvolatile migration, gravimeter, moisture permeameter
USP<921> Loss on Drying & Residue on Evaporation - Modern Instrumental Solution with Automated Water Bath Constant‑Weight Testing
USP<921> Loss on Drying & Residue on Evaporation - Modern Instrumental Solution with Automated Water Bath Constant‑Weight Testing
1. What Does USP<921> Require?
USP General Chapter <921> – Loss on Drying specifies how to determine volatile content in drugs, excipients, and related materials by:
Drying a pre‑weighed sample at a specified temperature (commonly 105 °C)
Weighing at intervals until two consecutive weighings do not differ by more than a defined amount (typically 0.3 mg or 0.5 mg) — i.e., constant weight
Similarly, Residue on Evaporation / Non‑volatile Matter tests (referenced across USP monographs and food contact material standards like 21 CFR & EU 10/2011) require:
Evaporation of solvent on a water bath (≤100 °C)
Drying residue to constant weight at 105 °C
Calculating % non‑volatile matter
📌 The key USP concept: "Constant weight" is numerically defined — not a visual or time‑based estimate.
2. Common USP <921>/ Residue Tests Pain Points
❌ Manual transfer: water bath → oven → desiccator → balance → back again
❌ Long cycle times (3–5 dry/cool/weigh loops = 2–6 hrs)
❌ Operator dependency in judging "dry enough"
❌ Hard to document for FDA 21 CFR Part 11 / GMP audits
❌ Balance damage from heat/humidity near ovens
3. Instrumented Alternative – LabStone ETR Series
The LabStone ETR Water Bath Evaporation & Constant Weight Tester fully supports USP <921>methodology:
USP Requirement | ETR Compliance |
|---|---|
Water bath evaporation (≤100°C) | ✅ Programmable evaporation temp. |
Dry at 105°C to constant weight | ✅ Drying chamber up to 140°C |
≤0.3 mg weight convergence | ✅ Auto‑weigh until Δ ≤ set threshold |
Reproducible, documented result | ✅ Time‑stamped data + audit trail (opt.) |
GMP / 21 CFR Part 11 | ✅ Optional GMP software module |
Workflow:
💧 Water Bath Evaporation → 🔥 High‑Temp Drying → ❄️ Controlled Cooling → ⚖️ Constant‑Temp Weighing (auto‑loop to constant weight)
Typically reaches constant weight in 2 drying cycles
Up to 69 samples in parallel
Optional solvent recovery ≥95%
4. Typical USP‑Related Applications
API / Excipient Loss on Drying (USP<921>)
Packaging extractables – Non‑volatile residue (per USP & FDAguidance)
Food contact material – Total migration residue (aligned with 21 CFR / EU frameworks)
Purified water / WFI – Insoluble/non‑volatile matter (pharmacopoeial analog)
5. Summary
Replacing manual execution of USP <921>Loss on Drying / Residue on Evaporation with a validated, automated constant‑weight system:
✅ Ensures USPmethodological compliance
✅ Improves precision & reproducibility
✅ Cuts analyst time dramatically
✅ Meets modern GMP data‑integrity expectations
LabStone ETR Series — USP‑ready automation for Loss on Drying and Residue on Evaporation testing.
Contact Us
Guangzhou Labstone Technology Co., Ltd
Add: Rm601, bldg A1, No. 2-6, Jinbao Rd, Baiyunhu Subdist., Baiyun District, Guangzhou,510430, Guangdong Province, P.R.China
Switchboard：+86(20)86406230 Technical：+86(20)86406337
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Email：market@labstone.cn
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