How to Read a Urea Specification and Certificate of Analysis

A urea specification is only as useful as your ability to read it against the product you actually need. Total nitrogen, biuret and moisture are the three lines that decide whether a cargo is fit for purpose; size distribution, free ammonia and the anti-caking treatment decide how it behaves once it arrives. Most disputes on urea cargoes start with a spec line that was vague, a test method that was never agreed, or a certificate that was accepted without being read.

This guide takes each line in turn, explains what it measures and why it matters, separates what is genuinely negotiable from what is not, and lists the red flags that should make you pause before you sign. Numbers quoted here are typical industry ranges for fertiliser-grade urea. Always check the contract specification, because that is what binds the seller.

Specification versus certificate of analysis

These two documents are often confused, and the difference matters.

The specification is the promise. It lists the parameters, the limits (usually a minimum or a maximum), and ideally the test method for each. It is agreed before the contract is signed and forms part of the contract.

The certificate of analysis (CoA) is the evidence. It reports the results for a particular lot, sampled at a particular time. It is issued by the producer's laboratory or, preferably as a cross-check, by an independent inspection company.

Three consequences follow:

1. A CoA that shows results inside the limits does not prove the whole cargo is inside the limits. It shows that the sample was.
2. A CoA without a lot number, date, sampling method or test method is of limited value.
3. If the specification is silent on a parameter, the CoA cannot be used to hold the seller to anything. Add the line you care about before you contract.

Total nitrogen

What it is. The percentage by weight of nitrogen in the product. Pure urea contains about 46.6% nitrogen by weight, which follows from its chemical formula. That is why commercial fertiliser urea is sold as "46%".

Typical specification. A minimum of 46.0% total nitrogen is the usual commercial floor. Some producers state a slightly higher minimum, but check the contract.

How to read it.

• Any result at or above the specified minimum passes. A result slightly above the minimum is normal.
• A reported figure above roughly 46.6% is physically impossible for urea. Treat it as a red flag for a transcription error, a faulty analysis or a document that has been altered.
• Nitrogen is usually measured by a Kjeldahl-type digestion or by an equivalent instrumental method. Ask which one was used, particularly if the figure looks too good.

What is negotiable. The minimum is rarely negotiable downward. If an offer is at a lower nitrogen minimum, the product is no longer standard 46% urea, and the price should reflect that. Use nitrogen content as the basis for comparing offers: a lower price for a lower-nitrogen product may cost more per unit of nitrogen.

Biuret

What it is. Biuret is a by-product formed when urea is exposed to high temperature during manufacture, essentially two urea molecules joined with the loss of ammonia. It is not a nutrient. At high concentrations it can harm plants, particularly seedlings and foliage.

Typical specification. A maximum of about 1.0% is commonly seen for fertiliser-grade urea. Product intended for foliar application, for horticulture or for application very close to seed usually needs a much lower figure, and low-biuret grades are priced separately.

How to read it.

• Match the limit to the use. For general broadcast application to field crops, a standard biuret limit is usually accepted. For foliar sprays, fertigation of sensitive crops or seed-row placement, ask for a low-biuret grade and put the number in the contract.
• Biuret generally correlates with the plant's process conditions. Product from some processes tends to carry lower levels than others, but do not assume. Read the number.
• Check the test method. Biuret is usually determined colorimetrically, and results are sensitive to sample preparation.

What is negotiable. The limit is negotiable in the sense that you can specify a stricter one if your end use needs it, usually at a premium. It is not sensible to accept a looser limit than your crop and application method can tolerate.

Red flags.

• No biuret line at all in the specification.
• A biuret figure given only as "typical" rather than "maximum".
• A very low figure on a product that is being offered at a standard price.

Moisture

What it is. Free water in the product, expressed as a percentage by weight. Urea is hygroscopic, so moisture is the most direct predictor of caking, lump formation and handling problems.

Typical specification. A maximum of around 0.5% is common. Some granular grades are specified lower. The tighter the limit, the better the margin against caking in humid conditions.

How to read it.

• Moisture figures depend heavily on the test method. Karl Fischer titration is widely used for urea because it measures water directly. A loss-on-drying method can give different results, because urea can lose other volatile substances when heated. Make sure the contract names the method.
• The figure on the CoA is the moisture at the time of sampling, usually at the plant. It says nothing about moisture picked up during storage, transport and loading. Moisture rises when the product is stored badly, bagged in damp conditions or exposed to rain or humid air.
• Compare the CoA moisture with a sample taken at loading and, where relevant, at discharge. A large rise tells you where the problem entered the chain.

What is negotiable. The limit is negotiable if you are prepared to accept a higher caking risk. Buyers with long supply chains, humid ports or extended storage normally ask for a tighter figure rather than a looser one.

Size distribution

What it is. The proportion of the product falling within a stated size range, determined by sieving. It matters for spreading, for blending and for the amount of dust the cargo produces.

Typical specification. Granular urea is usually specified in a range of roughly 2 to 4 mm. Prilled urea is usually specified in a smaller range, roughly 1 to 2.5 mm. In both cases the specification should state a minimum percentage that must fall within the range, and ideally a maximum for undersize and oversize fractions.

How to read it.

• A range on its own is incomplete. "2 to 4 mm" tells you nothing about how much of the product is actually inside that range. Ask for the minimum percentage within range and for the sieve sizes used.
• The undersize fraction matters most. Fines raise dust and caking and degrade blending.
• Some markets also specify a maximum for oversize material.
• Check which sieve series and standard were used, since results shift slightly between sieve sets.

What is negotiable. The range itself is often negotiable between standard offerings. A producer will have a typical range, and moving outside it may not be possible. What you can negotiate is the percentage within range and the limit on fines. If you blend, ask for a range that matches your other components. Our guide to prilled versus granular urea explains why size matching matters.

Red flags.

• A size range with no percentage.
• A CoA that lists only an average size.
• A sieve analysis that does not add up to 100%.

Crushing strength

Crushing strength is not always a formal specification line, but for granular urea it should be. It is the force needed to crush a single granule.

• Ask for the figure, the test method and the number of particles tested.
• Do not compare figures from different methods.
• If it is not in the specification, add it, with a minimum value and a named method.

Strength is linked to caking and dust, so it is worth paying attention to even though it appears on fewer certificates than nitrogen or moisture.

Free ammonia

What it is. Residual ammonia in the product, left over from manufacture. It is more commonly specified for technical and industrial grades than for standard fertiliser grades.

How to read it.

• A sharp ammonia smell on opening a bag or hold is an observation worth recording, and a reason to ask the producer for the figure.
• Free ammonia matters for industrial users, for example in resin production, because it can interfere with downstream chemistry.
• If your use is technical, require a maximum limit in the contract and name the test method.

What is negotiable. For fertiliser use, it is usually not a headline specification, and the practical approach is to ask whether the producer measures and reports it. For technical use, it should be a firm contractual limit.

Anti-caking treatment and formaldehyde

What it is. Urea is commonly treated to reduce caking and improve hardness. The treatment can be an additive included in the melt during granulation, a surface coating applied after production, or both. Formaldehyde-based conditioners are widely used on granular urea because they improve hardness and moisture resistance. Other treatments include oils, amines and fine mineral powders, depending on the producer.

Why you should read the line.

• The additive is part of what you are buying. Know what it is and at what level it is applied. It is normally a fraction of a percent by weight, but check the contract.
• Some end uses are sensitive to formaldehyde or coating residues, including technical applications and some regulated markets. Declare your end use at enquiry.
• Coatings can affect appearance and how the product behaves in blends. Two granular urea cargoes of the same size and strength can behave differently if the treatments differ.
• Some national authorities and customers ask for a declaration of additives. Ask the seller for a safety data sheet and a statement of the treatment.

What is negotiable. Whether the product is treated and with what, within the range the producer offers. If you need an untreated product or a particular treatment, say so at the outset, because it may limit which producers can supply.

Red flags.

• "Anti-caking agent: yes" with no substance named.
• A treatment that differs between the spec and the certificate.
• Refusal to provide a safety data sheet.

Other lines you may see

• Colour and appearance. Usually white or near-white. Visible discolouration, grey or brown particles, or foreign matter in a sample warrants investigation.
• Temperature at loading. Urea packed or loaded warm can cake on cooling. Ask what limit applies.
• Heavy metals and contaminants. Some markets regulate trace elements in fertilisers. If yours does, ask for the figures or a declaration in advance.
• Bulk density. Useful for stowage planning and for estimating bag counts.
• Packing and marking. Bag weight, material, inner liner, printing and lot marking are all part of what you receive.

What is negotiable and what is not

Usually fixed

• Minimum total nitrogen for the grade being offered.
• Fundamental product identity, for example a granular or a prilled product.
• Safety and regulatory documentation.

Negotiable within what the producer can supply

• A tighter biuret limit for sensitive end uses.
• The moisture maximum.
• The percentage within a size range and the fines limit.
• The anti-caking treatment, where alternatives exist.
• Packing, marking, and inspection arrangements.

Negotiable commercially

• Quantity tolerance at the seller's or the buyer's option.
• Price adjustment or rejection thresholds for off-specification material.
• The sampling and umpire procedure, including who appoints the inspection company and who pays.

Do not leave off-specification consequences to chance. A contract that says nothing about a price adjustment, a rejection right or an umpire leaves you arguing from a weak position.

Red flags checklist

Go through this list when you receive a specification or certificate.

1. No test methods named for the key parameters.
2. Total nitrogen reported above what is physically possible for urea.
3. CoA with no lot number, date or issuing laboratory, or an unsigned document.
4. Results that are suspiciously round or identical across successive certificates, which may indicate figures copied from a template rather than measured.
5. A CoA that predates production, or whose date is inconsistent with the vessel's loading dates.
6. "Typical" values offered where "maximum" or "minimum" values are needed.
7. A specification that omits biuret or moisture.
8. Pricing well below the market for the grade, with a story that explains why.
9. Unwillingness to allow independent pre-shipment inspection.
10. Product origin that is vague or changes between documents.

One red flag may have an innocent explanation. Several together should stop the deal until they are resolved.

Using independent inspection properly

A producer's CoA and an independent inspector's report serve different purposes. The producer's document shows its own quality control. The inspector's report is a check by a party with no stake in the sale.

A sensible arrangement:

• Appoint a recognised independent inspection company. Chemineral can arrange SGS or Intertek pre-shipment inspection.
• Define the scope: sampling during loading, analysis of named parameters, draft survey for weight, and hold inspection before loading.
• Agree in the contract how many samples are drawn and sealed, who holds them, and what happens if the producer's and inspector's results differ.
• Ask for the inspector's report to be issued to both parties at the same time.

Sample retention matters. If a dispute arises at discharge, a sealed retained sample taken at loading is the evidence that both sides can refer to.

A worked reading of a typical CoA

Take a hypothetical certificate for a granular urea lot. Work through it in this order, which puts the highest-impact lines first.

1. Identity. Check the producer, the product name, the lot or batch, the date of production and the date of analysis. All should be present and consistent with the shipment.
2. Total nitrogen. Confirm it is at or above the contract minimum, and not above what urea can physically contain.
3. Biuret. Compare with the maximum, and consider your end use.
4. Moisture. Check against the maximum and look at the test method named.
5. Size distribution. Confirm the percentage inside the specified range and the undersize fraction.
6. Strength and treatment. Check the crushing strength if the contract requires it, and the stated conditioning agent.
7. Free ammonia and other contract lines. Look for every parameter that appears in the specification and check that none has been dropped from the certificate.
8. Signature and issuer. An accredited laboratory, a named signatory and a date.

Then compare the certificate with the specification line by line. Anything on the specification that is missing from the certificate is a question for the seller.

Frequently asked questions

Why is urea sold as 46% nitrogen if the chemical maximum is slightly higher?

Pure urea contains about 46.6% nitrogen by weight. Commercial product contains small amounts of moisture, biuret and additives, so the practical figure is a little lower. A minimum of 46.0% is a common contractual floor.

What biuret level is acceptable?

It depends on the use. For general field application, a maximum of about 1.0% is commonly accepted. For foliar use, sensitive crops or seed-row placement, a much lower figure is needed. State the end use at enquiry and put the limit in the contract.

Is a higher moisture figure always a problem?

A higher figure raises caking risk, particularly in humid conditions and long storage. The test method also affects the number, so confirm how moisture was measured before comparing two certificates.

Do I need a formaldehyde figure?

For many agricultural users, a statement of the treatment is enough. If you serve a regulated market or a technical application sensitive to formaldehyde, ask for the additive and its level in writing and put a limit in the contract.

Who should issue the certificate?

The producer issues its own CoA, and an independent inspection company can verify it at loading. The independent report is the better basis for resolving a dispute because the inspector has no commercial interest in the outcome.

What if the cargo fails on discharge?

Your remedy depends on what the contract says. Without agreed sampling, an umpire and price-adjustment or rejection terms, the process is slow and uncertain. Agree these terms before the vessel sails.

Send us your specification

If you have a specification, a tender document or a certificate you would like checked against what the market can supply, send it with your RFQ to Chemineral's trade desk through the contact page. Tell us the grade, end use, packing and destination, and we will respond with a firm offer valid for 72 hours, loading from Sohar or Salalah, with SGS or Intertek pre-shipment inspection available on request. You can also review the prilled and granular urea product pages.