How to Read a DPG Certificate of Analysis and Check an Incoming Lot

Summary. A dipropylene glycol (DPG, CAS 25265-71-8) order is only as good as the paperwork you check against it. Confirm the grade and CAS number before ordering, read the batch Certificate of Analysis line by line against the technical data sheet, and run a short set of incoming checks when the drums arrive. The batch Certificate of Analysis governs over the TDS, and the SDS supplied with your order governs for hazard and handling.

Most DPG problems are paperwork problems that surface late: a different grade than expected, a CAS number that does not match across documents, or a water or colour result nobody compared with the specification. This guide is a working procedure, not a specification sheet. It is written by Supreme Petro Chemicals (SPC), a Chennai importer and bulk distributor; we supply DPG and do not manufacture it. For the full specification table, the grade comparison, storage notes and look-alike names, see the dipropylene glycol product page (sections grades, safety and storage and comparisons), which this guide deliberately does not repeat.

A five-step buyer workflow before you order DPG

1. Write down the end use. Fragrance carrier work and resin or plasticizer production ask different things of a glycol. Odour and colour matter most to the first; water and acidity matter most to the second (general knowledge).
2. Name the grade, not just the product. SPC supplies Fragrance / Perfumery Grade only and does not claim USP, food or pharma status for it. If you need a different quality, say so at the start.
3. Fix the CAS number. Use 25265-71-8, the commercial isomer mixture. A mismatch between the order, the CoA and the SDS is the first thing to resolve.
4. Ask who made it and who imported it. For SPC material the maker is SK picglobal Co., Ltd. (Ulsan, Korea) and the importer and drummer is Manali Petrochemicals Limited, Chennai. SPC itself is a trader.
5. Request the documents. The technical data sheet SPC-TDS-GLY-006 and the SDS are on the product page, and a batch Certificate of Analysis is supplied with every delivery. Send the quantity in drums and the delivery location and we quote within 4 working hours.

What each line on a DPG Certificate of Analysis means in practice

The limits sit on the TDS and the product page. Here the point is what to look for when your own lot's numbers arrive. The explanations are general knowledge about why each test exists, not SPC specifications.

DPG content and MPG

The assay is the headline purity figure, and it counts the isomers of dipropylene glycol together. The MPG line reports residual monopropylene glycol, a lighter related glycol. If your formulation is sensitive to related glycols, MPG is the line to watch, because a result close to its limit tells you more than a comfortable assay figure.

Specific gravity

Specific gravity at 20/20 C is mainly an identity and consistency check. It is also what converts kilograms to litres: at about 1.02, a 215 kg drum holds roughly 210 litres. That is a derived estimate, not a declared fill volume, so do not use it for invoicing.

Colour (APHA)

APHA colour is a visual clarity scale. It matters most where DPG goes into a clear fragrance or personal-care base, because a yellow tint carries straight into the finished product. Compare your lot's value with the limit, and where colour matters to you, look at the sample against a clean reference.

Water

Water is the line most affected by handling. Our SDS describes DPG as hygroscopic, so a drum that is left open, or a sample taken carelessly, will read higher than the CoA. If your result differs from the CoA, the first question is how the sample was taken and stored, not whether the lot was out of specification.

Acidity, iron, chloride and residue on ignition

These are trace-impurity lines. Acidity reports free acid, which can affect the stability of sensitive materials. Iron and chloride are trace contaminants that most buyers never test themselves but may care about in a sensitive product. Residue on ignition reports non-volatile mineral matter. For all four, the practical step is to read the batch figure and keep it on the lot record.

Boiling range and odour

A narrow boiling range suggests a consistent product. The odour line is a sensory release test: the manufacturer's CoA records characteristic, pass. We do not describe DPG as odourless. If odour is critical, assess the lot in your own base rather than relying on the CoA alone.

One caution on the numbers: values such as water and acidity are indicative TDS limits taken from the manufacturer's CoA, and the batch Certificate of Analysis for your lot is the figure that counts.

An incoming-lot checklist for DPG drums

Before opening or sampling a drum, wear the protective equipment the SDS supplied with your order specifies.

1. Match the paperwork. Order, delivery note, batch CoA and SDS should agree on the product name, CAS number 25265-71-8 and grade.
2. Check the drum. Confirm drum type, net weight and that closures are intact and labelled.
3. Compare the batch CoA with the TDS. Every parameter on the CoA should sit inside the TDS limit. Flag any line that is missing or has a different test basis.
4. Look at the liquid. It should be a clear, colourless liquid. Note any haze, particles or visible colour before the drum is opened for production.
5. Assess odour in your own base if odour matters to your product, using a small trial rather than a full batch.
6. Sample carefully. Use clean, dry containers, take the sample quickly, and reseal the drum straight away, because moisture uptake will distort a later water test.
7. Keep the records. File the batch CoA against the lot number you assign, so a later complaint can be traced.
8. Raise differences immediately. If your result disagrees with the CoA, tell us the lot details and we will pass them on.

Where to read hazard and handling information

Hazard classification, first aid, storage and transport status are in the SDS supplied with your order, which governs; read it before handling, and confirm transport status with your carrier before each shipment. Our guide to reading an SDS explains how to work through one. Storage and incompatibility notes are on the product page. Also see the CAS number procurement guide: pair every abbreviation with its CAS number and grade on the order.

How supply and quoting work

Chemical prices move with the market, so we publish no rate. Send the grade, quantity in drums and delivery location by call or WhatsApp on +91 86087 80096, or through the contact page, and we quote within 4 working hours. We supply from Chennai, with the warehouse at Redhills, and dispatch across South India.

The short version

• Confirm grade and CAS number 25265-71-8 before you order.
• Read the batch Certificate of Analysis against the TDS line by line; the batch CoA governs.
• Wear the protective equipment the SDS specifies, sample carefully and reseal drums, because DPG is hygroscopic.
• Read the SDS supplied with your order for hazard, first-aid and transport information.
• Keep the batch CoA with your lot record.