Everything you need to know
Residual solvents are organic volatile chemicals used in the manufacture of drug substances, excipients, or pharmaceutical products that remain in the finished product. USP <467> classifies solvents by their toxicity profile and establishes acceptable limits. This guide explains the classes, methods, and when testing is required.
What are residual solvents and why do they end up in supplements?
Residual solvents are organic chemicals — alcohols, ketones, hydrocarbons, chlorinated solvents — used in extracting or processing botanical ingredients, pharmaceutical actives, or supplement components. They can remain in the finished product at low levels after manufacturing. Common sources include: ethanol extraction of herbal tinctures and botanicals; hydrocarbon (butane, propane) extraction of hemp and cannabis; heptane or acetone use in chromatographic purification; methanol or acetonitrile in pharmaceutical synthesis; and propylene glycol or glycerin in liquid supplement formulations.
What are USP Class 1, 2, and 3 solvents?
USP <467> divides residual solvents into three classes based on toxicity: Class 1 (avoid if possible) — known or suspected human carcinogens with no acceptable exposure: benzene (2 ppm limit), carbon tetrachloride (4 ppm), 1,2-dichloroethane (5 ppm), 1,1-dichloroethene (8 ppm). Class 2 (limit exposure) — non-genotoxic animal carcinogens or potential CNS/organ toxins: acetonitrile (410 ppm), methanol (3000 ppm), hexane (290 ppm), toluene (890 ppm), DCM (600 ppm). Class 3 (low toxicity) — generally regarded as safer solvents: ethanol (5000 ppm), acetone (5000 ppm), isopropanol (5000 ppm), ethyl acetate (5000 ppm).
What analytical method is used for residual solvents testing?
The standard method is headspace gas chromatography with mass spectrometry (headspace GC-MS) or GC with flame ionization detection (GC-FID). In headspace GC, a sealed sample vial is heated to volatilize the solvents into the headspace above the sample. The headspace gas is then injected into the GC column. This technique minimizes sample preparation artifacts and works well for both solid (powder, capsule fill) and liquid (tincture, extract) matrices. USP <467> specifies two procedures: Procedure A (general screen) and Procedure B (targeted analysis for known solvents).
When is residual solvents testing required for dietary supplements?
Residual solvents testing is not federally mandated for dietary supplements the way it is for pharmaceutical products. However, testing is strongly recommended or required in these situations: (1) your formulation contains botanicals extracted with solvents; (2) you use hemp or cannabis extracts; (3) you are selling to markets that require it (Whole Foods, major supplement retailers, EU); (4) your label makes specific purity claims; (5) you are a contract manufacturer producing for pharmaceutical or nutraceutical clients. Most supplement GMP programs include residual solvents testing as a standard quality attribute.
What is the typical turnaround for residual solvents testing?
Standard turnaround at Prodigy Labs is 5–10 business days from sample receipt. Rush service (2–3 business days) is available for urgent batch release decisions. Simple matrices (pure ethanol tinctures, standard capsules) tend to process faster than complex matrices (CO2 extracts, multi-ingredient blends) that require additional validation steps.
What results does a residual solvents COA include?
A residual solvents COA from Prodigy Labs includes: individual quantitative results for each detected solvent (in ppm); the limit of quantitation (LOQ) for each solvent; pass/fail determination vs. USP <467> limits; the test method reference (USP <467> Procedure A or B); chromatographic conditions; and the analyst signature with date. Undetected solvents are reported as "<LOQ" or "<LOD" with the relevant detection limit shown. Learn more about our residual solvents testing services.