Summary. A technical data sheet (TDS) states the limits a PEG grade is supplied against; a batch Certificate of Analysis (CoA) states what that batch measured. For PEG 400 the key limits are average molecular weight 380.0 to 420.0 and hydroxyl value 265.0 to 295.0 mg KOH/g. Compare each CoA result with the matching data sheet, and never mix limits between standards.
Why read the data sheet line by line
Polyethylene glycol (PEG) is sold under a single CAS number, 25322-68-3, whatever its size. That makes the name on an invoice a poor guide to what is in the drum. The real definition of the material is on its data sheet and on the batch CoA. This guide walks through the two PEG data sheets on our PEG 200 to 6000 product page: SPC-TDS-GLY-008 (PEG-400, IP / pharmacopoeial) and SPC-TDS-GLY-022 (USP, covering PEG-400 and PEG-3350).
Supreme Petro Chemicals is a trader and distributor in Chennai, not a manufacturer. The values below come from the producer's Certificate of Analysis, with the producer named on the downloadable data sheet, as summarised in our data sheets. They apply to the grades on those sheets only. A batch Certificate of Analysis is supplied with every delivery.
TDS versus batch CoA
A TDS gives the limits a grade is supplied against. A CoA gives the measured result for one batch. A good incoming-inspection habit is simple: put the CoA beside the TDS and tick each line. If a parameter is on the TDS but missing from the CoA, ask why before you accept the batch. If the CoA reports a method or standard you do not recognise, ask for it.
The PEG-400 IP data sheet, line by line
| Parameter | Limit | Note |
|---|---|---|
| Appearance at 25 C | Clear liquid | Clear liquid, per the data sheet |
| pH (5% solution) | 4.5 to 7.5 | Slightly acidic to neutral range |
| Moisture (w/w) | 0.20% max | General knowledge: PEG is hygroscopic, so this is the line to watch in storage |
| Colour (APHA) | 25.0 max | APHA colour scale |
| Hydroxyl value | 265.0 to 295.0 mg KOH/g | Linked to chain length (see below) |
| Viscosity at 98.9 C | 7.00 to 8.00 cSt | Measured at 98.9 C |
| Residue on ignition | 0.05% max | General knowledge: inorganic residue after burning |
| Average molecular weight | 380.0 to 420.0 | The number in the name |
| Free ethylene oxide | 10.0 ppm max | General knowledge: residual monomer |
| 1,4-Dioxane | 10.0 ppm max | Impurity limit |
Source: SPC-TDS-GLY-008, from the producer's Certificate of Analysis. Notes marked general knowledge are not part of the data sheet.
Hydroxyl value and average molecular weight
General chemistry: a linear PEG chain has one hydroxyl group at each end, so the hydroxyl value is inversely related to molecular weight. The rule of thumb is average molecular weight = 56,110 x 2 / hydroxyl value (in mg KOH/g). For PEG 400, a hydroxyl value of 280 gives about 401, which sits in the middle of the 380.0 to 420.0 range on the data sheet. The limits 265.0 and 295.0 work out to roughly 423 and 380. That is why the two lines should agree on a good batch: if the CoA hydroxyl value and average molecular weight tell different stories, query it.
The same logic applies approximately to PEG-3350 on the USP sheet. Its hydroxyl value of 30 to 38 mg KOH/g and average molecular weight of 3015 to 3685 describe broadly the same chain length from two directions, though the rule of thumb does not reproduce the sheet's range exactly. The hydroxyl value gets small for large chains, so a few units of error matter much more for PEG 3350 than for PEG 400.
Viscosity: temperature matters
The data sheet quotes viscosity at 98.9 C (7.00 to 8.00 cSt for the IP sheet, 6.80 to 8.00 cSt on the USP sheet). Our safety data sheet gives an approximate 90 to 110 cSt at 20 C. These are not in conflict; they are the same liquid at two temperatures. Never compare a viscosity from a CoA at one temperature with a limit at another.
The USP data sheet
| Parameter | PEG-400 USP | PEG-3350 USP |
|---|---|---|
| Assay | 95.0 to 105.0% | 97.0 to 103.0% |
| pH (5% solution) | 4.5 to 7.5 | Not listed |
| Viscosity at 98.9 C | 6.80 to 8.00 cSt | Not listed |
| Moisture | Not listed | 1.0% max |
| Hydroxyl value | Not listed | 30 to 38 mg KOH/g |
| Average molecular weight | Not listed | 3015 to 3685 |
| MEG + DEG | 0.25% max | 0.20% max |
| Residue on ignition | 0.10% max | Not listed |
| Free ethylene oxide | 10 ppm max | 1 ppm max |
| 1,4-Dioxane | 10 ppm max | 10 ppm max |
| Formaldehyde | Not listed | 30 ppm max |
Source: SPC-TDS-GLY-022. Not listed means the sheet does not state the parameter.
Why the impurity limits exist
General knowledge: free ethylene oxide and 1,4-dioxane are residues associated with how polyethylene glycol is produced, and mono and diethylene glycol (MEG and DEG) are related glycol impurities. Regulated pharmaceutical standards put tight limits on them for that reason. The DEG angle is particularly important in oral liquids; see our guide to DEG and EG testing for glycerine, propylene glycol, sorbitol and PEG.
Do not mix standards
The most common reading mistake is lifting a number from one sheet and applying it to another. Moisture is 0.20% max on the PEG-400 IP sheet but 1.0% max on the PEG-3350 USP line. Free ethylene oxide is 10 ppm max for PEG-400 and 1 ppm max for PEG-3350. Use only the limits on the data sheet that matches the grade you ordered. For background on what the label means, see what USP grade means.
A short incoming-inspection checklist
- Confirm the PEG number and the standard (IP / pharmacopoeial or USP) on the CoA match your order.
- Check that average molecular weight and hydroxyl value agree with each other and sit inside the limits.
- Check viscosity was measured at the temperature the limit refers to.
- Check moisture, because PEG takes up water if a container is left open.
- Check ethylene oxide, 1,4-dioxane and, where listed, MEG + DEG.
- Keep the CoA with the batch record.
What this page does not claim
We hold technical data sheets for PEG-400 (IP and USP) and PEG-3350 (USP) only. We do not publish data sheets for PEG 200, 600, 2000, 4000 or 6000, and we do not claim food-grade or cosmetic-grade material. If you need one of those, ask for the document before you order. We quote within 4 working hours: call or WhatsApp +91 86087 80096. For the wider glycol family, see our glycol supplier guide.