Summary. The technical data sheet (TDS) states the limits a grade is supplied against; the batch Certificate of Analysis (CoA) states what one lot measured. This guide is about the second step: checking a DEG CoA line by line, treating Report lines correctly, comparing several lots and knowing what to ask for. The full list of limits is on the Diethylene Glycol (DEG) product page, and DEG is for industrial use only.
Who this guide is for
Quality and purchase teams that receive a batch Certificate of Analysis with each delivery of diethylene glycol (CAS 111-46-6) and want a repeatable way to accept or query the lot. Supreme Petro Chemicals is a Chennai trader and bulk distributor, not a manufacturer, and supplies Industrial Grade DEG with a batch Certificate of Analysis with every delivery. The limits quoted here come from SPC technical data sheet SPC-TDS-GLY-001, which is drawn from the producers' batch CoAs; we do not repeat the full table, because it already sits on the product page.
The nine lines on that sheet fall into three groups, and each group is read differently.
- Hard limits with a minimum: DEG content, 99.80% wt minimum. The result must be at or above the figure.
- Hard limits with a maximum: MEG + TEG (2000 mg/kg), water (0.100%), colour (10 Pt-Co) and acidity as acetic acid (0.0050% wt). The result must be at or below the figure.
- Range and Report lines: specific gravity (1.1170 to 1.1200 at 20/20 °C), appearance (clear and colourless), distillation initial boiling point and dry point. The first two have a stated range or description; the last two are marked Report.
A worked example, line by line
The figures below are invented for illustration only. They are not from any real lot and not an SPC result. The point is the method: write the CoA figure next to the limit, state whether it passes, and note how much margin remains.
| Line | Illustrative CoA result | Limit | Reading |
|---|---|---|---|
| DEG content | 99.91% wt | 99.80 min | Passes, 0.11 points above the floor |
| MEG + TEG | 1200 mg/kg | 2000 max | Passes, 800 mg/kg of headroom |
| Water | 0.085% | 0.100 max | Passes, but 85% of the allowance is used |
| Colour | 5 Pt-Co | 10 max | Passes |
| Acidity as acetic acid | 0.0060% wt | 0.0050 max | Fails: query the lot before acceptance |
| Specific gravity | 1.1185 | 1.1170 to 1.1200 | Inside the range |
Three habits come out of this example. First, a lot can pass five lines and fail one; one failure is enough to hold the material. Second, headroom matters: a water result at 85% of its limit passes today but leaves little room for pick-up once containers are opened, because DEG is hygroscopic. Third, a compliance statement is not a figure. If the CoA says only that a line is within specification, ask for the number.
How to treat Report lines
Two lines on the data sheet, the distillation initial boiling point at 760 mmHg and the dry point (including 246 °C), are marked Report. That means the CoA should show the measured reading, but the data sheet does not set a pass or fail value. Two practical consequences follow.
- A missing reading is a documentation gap, not a failure. Ask the supplier to supply the figure; do not assume it was within range.
- A reported reading is still useful. It gives you a baseline for that producer's material, and a shift in the reading between lots is a reason to ask a question even though no limit has been crossed.
If your own process needs a firm limit on a Report line, say so when you enquire so that the requirement can be compared with the producer's CoA before an order is placed.
Comparing a CoA across lots
A single CoA tells you about one lot. A small table kept over several deliveries tells you about the supply. For each delivery, record the batch number, the date received and the figure for the lines that matter to your process. Then look for these patterns:
- Drift towards a limit. Water, colour and acidity are maximum-limit lines. A series such as 0.040%, 0.065%, 0.085% for water is still passing but moving the wrong way.
- Sudden jumps in MEG + TEG. The combined figure is a measure of neighbouring glycols. A step change between lots is worth raising even when the result is below 2000 mg/kg.
- A change of producer. The data sheet states the limits are met by both makers named there. Ask which producer made the lot, and if you are told it changed between deliveries, compare the two CoAs line by line.
- Different test dates or methods. Check that results you are comparing were measured the same way, and that percent by weight is not being compared with a volume figure.
Keep the CoA with your receiving record so any later problem can be traced to a lot.
The Report and reference lines to ask for
When you request documents before an order, these are the items worth naming:
- The current technical data sheet, SPC-TDS-GLY-001, so you can see the limits.
- The safety data sheet, Rev 3.1, for hazards, handling, storage and transport.
- Which producer the offered lot comes from.
- The distillation initial boiling point and dry point readings on the CoA, since they are Report lines.
- Any tighter limit of your own, stated in writing, so it can be compared with the CoA.
An incoming-inspection checklist
- Confirm the product name and CAS number on the CoA: diethylene glycol, 111-46-6.
- Match the batch number to the drum label or tanker paperwork.
- Check DEG content is 99.80% wt or higher.
- Check MEG + TEG is 2000 mg/kg or lower.
- Check water is 0.100% or lower, colour 10 Pt-Co or lower and acidity 0.0050% wt or lower.
- Check that the two distillation lines are reported.
- Check appearance and specific gravity on receipt if you have the means.
- Enter the figures in your lot comparison table and file the CoA.
What a CoA cannot tell you
A CoA describes one lot at one moment. It does not tell you how the material was stored afterwards, and it cannot confirm suitability for your own process. SPC's safety data sheet restricts DEG to industrial and professional use, and says it is not for food-contact or pharmaceutical end-use without regulatory confirmation. Industrial Grade DEG is not food, pharma or cosmetic grade, and a CoA for it does not change that.
DEG is harmful if swallowed. How edible and pharmaceutical excipients are tested for DEG and EG is a separate subject, covered with what is and is not confirmed in our guide on DEG and EG testing of glycerine, propylene glycol, sorbitol and PEG.
Storage after delivery keeps the CoA true
The safety data sheet advises storing DEG in original, tightly closed containers of stainless steel, mild steel or HDPE at 15 to 30 °C, protected from freezing and away from strong oxidisers and concentrated acids. Because DEG is hygroscopic, good closure is what keeps the water line on the CoA true after the drum is opened. See our glycol sourcing guide for how DEG fits with MEG, propylene glycol and PEG.
Frequently asked questions
Is the TDS the same as the CoA?
No. The TDS lists the limits a grade is supplied against and is the same for every lot. The CoA is the measured result for one batch.
What if a CoA line is only marked as within specification?
Ask for the measured figure. A statement without a number cannot be compared with another lot or checked against your own limit.
Can I use Industrial Grade DEG in food or medicine?
No. SPC supplies Industrial Grade DEG for industrial use only. Technical grade is not food or pharma grade.
Get a quote
To discuss diethylene glycol, call or WhatsApp Sanketh on +91 86087 80096 or use the enquiry form on the Diethylene Glycol (DEG) product page. Tell us the pack (bulk tanker or 230 kg drums), the quantity, your location and your industrial use. We quote within 4 working hours.