How to read a COA and SDS before buying industrial chemicals.

Before you buy industrial chemicals, two documents tell you almost everything you need to know: the Certificate of Analysis (COA) and the Safety Data Sheet (SDS). The COA is a batch-specific test report that shows whether the material actually meets your specification; the SDS is a 16-section safety document that explains the chemical’s hazards and how to handle, store, transport and respond to it.

Reading a COA and SDS correctly is how you verify quality and manage safety before a drum ever reaches your plant — not after it has caused a problem. Read the COA line by line against your own agreed specification, checking each measured value, its unit and the test method used. Read the SDS for the GHS hazard class, the handling and storage rules, and the transport classification. Getting this right protects your product quality, your workers and your regulatory standing; getting it wrong can mean an off-spec batch in your process or an unsafe material on your dock.

Most buyers only learn to read these documents properly after something has already gone wrong once — a batch that passed on paper but behaved differently in the plant, or a consignment that sat at the port because a transport entry did not match the packing. Both outcomes are avoidable, and neither requires a chemistry degree; they require knowing which six or seven fields on each document actually carry the risk, and checking those fields every time rather than skimming for the word “pass.”

This guide walks through both documents field by field, with a cheat sheet for the SDS’s 16 sections, a worked example of a COA table, regional regulatory context, a note on where digital and QR-coded documentation is heading, a glossary and a red-flag list — so you can evaluate any range of industrial chemicals with confidence, whatever the grade, the origin or the destination port.

COA and SDS at a Glance

What Is a Certificate of Analysis (COA), and What Should It Contain?

A Certificate of Analysis is a document in which the manufacturer certifies that a specific batch of material was tested and met its specification. A complete COA identifies the product name and grade, the batch or lot number, and the manufacturing date with a retest or expiry date where relevant. The heart of the COA is a table: for each parameter it lists the specification limit, the actual measured result, and the test method used to obtain it.

Typical parameters include assay or purity, individual and total impurities, moisture or water content, residue on ignition or ash, melting or boiling point, and appearance or colour. For intermediates the isomer ratio often matters as much as purity. The COA should also name the manufacturer and carry an authorised signatory or quality-control stamp.

A product such as sulfuric acid will show strength and heavy-metal limits, while an aromatic agrochemical intermediate will show assay and isomer content. If any of these elements is missing, the COA is incomplete — ask for a corrected, batch-specific document before you commit.

The elements a complete COA always carries

Start with identity: the product name and grade should match your purchase order exactly, and where the product has one, the CAS number should be printed on the sheet rather than left for you to infer. The batch or lot number matters more than almost anything else on the page, because it is the single detail that ties the paper in your hand to the drum sitting on the dock — a COA without one is a description of the product in general, not evidence about the consignment you are about to receive. Dates matter for the same reason: a manufacturing date tells you when the batch was made, and a retest or expiry date tells you whether the figures on the page are still trustworthy by the time the material reaches you, which matters a great deal for anything moisture- or temperature-sensitive.

The centre of the document is the parameter table itself — specification limit, measured result and test method, repeated for every property that was actually tested, not a subset chosen to look favourable. And finally, a COA should be signed off: a manufacturer name alongside an authorised signatory or a quality-control stamp is what turns a spreadsheet of numbers into a document someone is willing to stand behind. A sheet missing any one of these is still useful as a reference, but it is not yet the evidence you need before you commit to a container.

What Is a Safety Data Sheet (SDS), and What Do Its 16 Sections Mean?

A Safety Data Sheet is a standardised hazard document with 16 sections in a fixed order, set by the Globally Harmonized System (GHS). Because the order never changes, you can find any piece of information quickly once you know the layout.

When you are buying, sections 2, 7, 10 and 14 carry the most immediate weight: they tell you the hazard class and signal word, how to store and handle the material, what it is incompatible with, and how it must be shipped. A material such as nitrobenzene carries serious health hazards, and its SDS states them plainly — which is exactly why you read the SDS before the material arrives, not after.

The 16 SDS Sections, One Line Each

This is the fixed GHS running order. Keep it beside you the first few times you review a sheet and you will stop hunting for information you already know is there somewhere.

How Do You Read a COA Against Your Own Specification?

You read a COA against your own specification by checking it parameter by parameter, not by trusting the word “pass” at the bottom. Put your specification and the COA side by side and confirm three things for every line: that the parameter is the one you actually require, that the unit matches (percent versus parts per million, for example), and that the measured result sits inside your limit with enough margin for your process.

Then confirm traceability. The batch or lot number on the COA must match the number stencilled on the drums or bags you receive, so the certificate belongs to the material in front of you. Check the test method against your own, because a result that passes one method can fail another. Watch the parameters that drive your process — for a dye intermediate that may be isomer content and assay; for a process acid it may be strength and chloride. A COA that is generic, undated, or shared across several lots is not evidence about your batch; insist on the specific one.

A Worked Example: Reading a Sample COA Table

The table below is an illustrative COA layout for a generic aliphatic amine — not a real certificate — to show how the three columns work together. Notice that a measured result sitting well inside the limit, with the method stated, is what you are looking for in every row.

Reading this the right way means checking the method column as closely as the result — a 99.4% assay by GC is not directly comparable to a 99.4% assay by titration if your own QC lab only runs one of the two.

What Hazard Information on the SDS Matters Most Before You Buy?

The hazard information that matters most before you buy sits in a handful of SDS sections. Section 2 gives the GHS classification, the signal word (“Danger” or “Warning”), the hazard (H) statements and precautionary (P) statements — your first read on how dangerous the material is. Section 8 lists occupational exposure limits and the personal protective equipment your team will need, which has direct cost and facility implications.

Section 7 covers handling and storage, including temperature, ventilation and the materials the chemical must be kept away from; section 10 adds stability and reactivity, flagging conditions and incompatibilities to avoid. Section 14 gives the transport classification — the UN number, hazard class and packing group — which determines how the material is shipped and what your receiving dock must be ready for.

Reading these before placing an order tells you whether you can store, handle and transport the chemical safely with the facilities you already have, or whether you need to prepare first. This is the practical half of reading a COA and SDS: the COA protects your process, the SDS protects your people.

How Should You Review a COA and SDS Before Placing an Order?

Reviewing a COA and SDS before an order is a short, repeatable routine. The six steps below take minutes once they are habit and save far more than they cost.

1. Confirm identity and traceability. Check that the product name, grade, CAS number and batch or lot number on the COA match what you are buying, and that the document is dated. Without a lot number and date, a COA cannot be tied to a specific delivery.
2. Compare the COA to your specification. Place your spec beside the COA and check every parameter, its unit and its limit against the measured result. Confirm each value sits inside your tolerance with working margin, not just barely inside the supplier’s own limit.
3. Verify test methods and tolerances. Check that the COA cites the test method for each parameter and that it matches your laboratory’s method. Where methods differ, agree a single reference method so results reconcile on receipt.
4. Read the SDS hazard and composition sections. Read sections 2 and 3 for the GHS class, signal word, hazard statements and composition. This tells you how hazardous the material is and what is actually in it.
5. Check handling, storage and transport. Read sections 7, 10 and 14 for storage conditions, incompatibilities, reactivity and the UN transport classification, and confirm your facility and receiving process can meet them.
6. File the documents and reconcile on receipt. Keep the current SDS available to the people who handle the material, and on delivery match the batch COA to your incoming inspection before releasing the lot to production.

What Do You Do When the COA and Your Own Inspection Disagree?

Sooner or later, on a critical enough material, your laboratory will come back with a number that does not match the batch COA. The instinct is to treat this as an accusation, but it is better treated as a diagnostic question: is the difference inside the normal spread you would expect between two laboratories running the same method, or is it large enough that one of you is simply wrong? A one or two percent drift on an assay run by the same titration method at both ends is often nothing more than ordinary method variability; a result that is outside your specification by a wide margin, or that used a different method entirely, is a different conversation.

The first move is always to compare like with like. Ask the supplier for their retained sample from the same batch and run both samples side by side, ideally by the same method in the same laboratory, before anyone argues about whose number is correct. If the retained sample confirms your result, you have a genuine out-of-specification batch and a conversation about replacement, credit or return follows naturally from your commercial terms. If the retained sample agrees with the original COA, the disagreement is almost always a sampling or method issue on one side, and the fix is procedural rather than commercial — an agreed reference method going forward removes the argument before it starts a second time. Either way, the retained sample is what turns a dispute about trust into a question that data can actually answer, which is exactly why it is worth confirming a supplier holds one before you place a first order.

Where Did the COA and SDS Come From?

Both documents grew out of long efforts to standardise quality and safety. The Certificate of Analysis has roots in pharmacopoeial and quality-assurance practice, where buyers needed proof that a batch met a defined standard; modern quality systems such as ISO 9001 formalised the traceability — lot numbers, test methods and records — that a good COA now reflects.

The Safety Data Sheet evolved from the older Material Safety Data Sheet (MSDS), which varied widely in format from one supplier to the next. Standardisation came with the United Nations Globally Harmonized System of Classification and Labelling of Chemicals (GHS), first published in 2003, which defined the 16-section SDS and the familiar hazard pictograms.

Major markets then aligned their own rules to it — the United States through OSHA’s Hazard Communication Standard in 2012, the European Union through REACH and the CLP regulation, and many others through GHS-based national standards. Today the format is broadly harmonised worldwide, though regional annexes still differ, which is why export-oriented manufacturers in India and elsewhere issue GHS-compliant sheets. The practical takeaway for a buyer is constant: whatever the market, a complete COA and SDS are the baseline evidence of quality and safety.

How Do Regional Rules Differ?

The 16-section skeleton is global, but the annexes around it are not. If you import into more than one country, expect the same product to arrive with SDS variants that look almost identical but differ in a few load-bearing details.

For an export shipment the practical point is section 14 and section 15 together: the UN number and packing group usually travel unchanged, but the regulatory references and permitted transport mode can vary by destination. Raise your destination country and transport mode at enquiry stage so the correct annex is already on the sheet you receive, rather than being requested after the consignment is packed. If you buy into several markets from the same supplier, it is worth asking directly whether they maintain a single master SDS that gets a regional annex swapped in per destination, or whether each market gets a separately authored sheet — the first approach tends to stay more consistent on the hazard core while still meeting local language and citation requirements, and it is a reasonable question to put to any supplier shipping to more than one country.

Where Digital and QR-Coded Documentation Is Heading

Paper and PDF documentation is still the norm, but a growing number of manufacturers are moving batch COAs and SDSs onto systems a buyer can query directly rather than file away. A QR code printed on the drum label or packing list that resolves to the exact batch’s certificate removes an entire category of error — the wrong COA attached to the wrong email, a lot number typed incorrectly into a spreadsheet, a document that quietly fails to get forwarded past a purchasing desk to the people who actually need it on the shop floor. It also makes the traceability question from earlier in this guide almost trivial to answer: scan the drum, see the batch’s own figures, compare them to your specification on the spot.

The same shift is happening with SDS distribution through regional compliance databases, which exist precisely so that a facility can confirm it is looking at the current, correctly localised version of a sheet rather than a copy someone saved three revisions ago. None of this changes what you are checking — the parameters, the methods, the hazard sections and the transport classification are exactly the same fields this guide has walked through — but it does change how quickly a mismatch surfaces. A buyer evaluating new suppliers can reasonably ask whether batch documentation is available this way, not as a requirement, but as one more signal of how seriously a supplier treats its own paperwork.

Why Documentation Quality Signals Supplier Reliability

The condition of a supplier’s COA and SDS tells you something beyond the batch in front of you. A document that is complete, dated, correctly signed and written in the current format is evidence of a quality system that is actually being followed day to day, not assembled for your benefit. The reverse is just as informative: a supplier who is slow to produce a batch-specific COA before the first order, who sends an SDS that still carries last year’s revision date, or who cannot explain a test method when asked, is telling you how the next twenty orders are likely to go, not just this one.

This is worth treating as a genuine evaluation criterion alongside price and lead time, because documentation problems rarely stay contained to paperwork. A manufacturer careless enough to let an SDS lapse past its revision date is statistically more likely to also be careless about the process controls that keep a batch inside specification in the first place. Buyers who weigh documentation discipline into their supplier selection, rather than treating it as an administrative afterthought once commercial terms are agreed, tend to spend far less time later chasing corrected certificates or explaining discrepancies to their own quality department.

What Are the Red Flags in a COA or SDS?

The clearest red flag is a COA with no batch or lot number, no date, or no test methods — it cannot be tied to your delivery or verified. Be wary of a single COA reused across multiple lots, results that sit exactly on the limit for every parameter, or values quoted without units. On the SDS side, watch for a missing or old revision date, a sheet that names a different grade or product, or empty sections where hazard, transport or first-aid information should be.

Other warning signs are a supplier who cannot provide either document before shipment, documentation that does not match the material actually delivered, or an SDS that downplays a known hazard. A dependable supplier does the opposite: it issues a batch-specific COA and a current, grade-specific SDS as a matter of course, cites its methods, and states hazards honestly. If you have to chase basic documentation before the first order, treat that as information about every order to come.

Glossary of Terms

COA

Certificate of Analysis — a batch-specific test report certifying that one lot met its specification.

SDS

Safety Data Sheet — the 16-section GHS hazard document issued per product and grade.

MSDS

Material Safety Data Sheet — the pre-GHS predecessor to the SDS, now largely superseded.

GHS

Globally Harmonized System of Classification and Labelling of Chemicals — the UN framework standardising hazard communication.

CAS number

A unique numeric identifier assigned to a chemical substance by the Chemical Abstracts Service.

UN number

A four-digit code identifying a hazardous substance for transport purposes.

Packing group

A classification (I, II or III) indicating the degree of danger a substance presents in transport.

Assay

The measured purity or active-content level of a chemical, usually expressed as a percentage.

LOD / LOI

Loss on drying / loss on ignition — common methods for measuring moisture or volatile content.

H- and P-statements

Standardised GHS hazard (H) and precautionary (P) statements printed in SDS section 2.

Karl Fischer

A titration method for water content, often specified where moisture is critical to a process.

Retained sample

Material held back by the manufacturer from a batch, so a later dispute can be tested rather than argued.

Retest date

The date by which a batch should be re-tested to confirm the COA figures still hold.

APHA / Hazen

A colour scale used for clear liquids, where a lower number means a water-whiter product.

Isomer ratio

The proportion of structural isomers in a product — often as important as assay for intermediates.

Incoming inspection

The buyer’s own test on arrival, reconciled against the supplied batch COA before release to production.

Five Minutes, Before You Click Order