How to Check an Ortho Xylene CoA Against the TDS Before You Accept a Tanker

Summary. An ortho xylene (o-xylene, CAS 95-47-6) certificate lists an assay plus a set of impurity limits. The assay says how much o-xylene is present; the impurity lines say what else is in the tanker. This guide is about how to read the paperwork: which document says what, in what order to read a certificate, how to compare each result with the TDS limit, and what to check when the tanker arrives. The full 13-line specification table is on the ortho xylene product page, so it is not repeated here.

Four documents, four different jobs

Buyers often use these terms loosely, so separate them first.

For the ortho xylene we supply, the TDS (SPC-TDS-ARO-005) reproduces the limits from a Certificate of Quality issued by Reliance Industries Limited, Jamnagar Manufacturing Division, Gujarat. A batch Certificate of Analysis is supplied with every delivery. Supreme Petro Chemicals is a Chennai supplier and bulk distributor, not a manufacturer, so always read the producer named on the certificate rather than assuming one.

A reading order for any ortho xylene certificate

1. Product name, CAS number (95-47-6) and grade wording. Mixed xylene is CAS 1330-20-7 and a different product.
2. Producer and laboratory named on the certificate.
3. Batch or lot number, and a date that fits the consignment.
4. Assay, with unit, basis and limit.
5. Each impurity line, with unit and limit.
6. Physical lines: appearance, colour, specific gravity, acidity.

Assay: read the basis, not just the number

• Unit and basis. Our figure is 98.50 wt% minimum. A weight percent and a volume percent are not interchangeable.
• Minimum versus measured. The TDS gives the limit the grade is supplied against. The batch CoA gives the result for your consignment.
• Grade wording. The grade is petrochemical (technical) grade, not reagent, food or pharma grade, so a reagent-catalogue purity is not a like-for-like comparison.

A limit-by-limit comparison method

Put the TDS beside the batch CoA and walk down the lines. For every parameter ask three questions: is the line present, is the unit the same, and is the result inside the limit? The examples below use limits from our TDS and are illustrative only, not results from any real batch.

• Maximum lines. Cumene has a limit of 0.250 wt% max. A result of 0.200 passes; a result of 0.300 fails. A result reported as a less-than figure is fine if it is below the limit.
• Minimum line. The assay limit is 98.50 wt% min, so a result below that fails, and one only marginally above it leaves little headroom.
• Range line. Specific gravity at 15.5/15.5 C must sit between 0.8820 and 0.8850. Check both ends, and check that the reference temperatures match.
• Unit traps. Sulphur and styrene are in wt ppm, bromine index is in mg/100 g, colour is on the Pt-Co scale, and the remaining composition lines are in wt%. A certificate that mixes units without saying so cannot be compared safely.
• Missing lines. If the TDS has a line the CoA does not report, ask for it before you accept the consignment.

A worked example: one impurity line, with its unit

Take styrene. The TDS limit is 20 wt ppm max. Suppose a certificate shows styrene as 0.002. If that figure is in wt%, it equals 20 wt ppm, exactly on the limit. If it is in wt ppm, it is far below the limit. The two readings lead to very different conclusions, which is why the unit printed beside the number matters as much as the number. The same care applies to sulphur: 1.0 wt ppm max on the TDS is a thousand times tighter than 1.0 wt%. This example is illustrative only and does not describe any real batch.

Where the phthalic anhydride link matters

Ortho xylene is bought mainly as the feedstock for phthalic anhydride, so a converter reads the impurity lines closely; your own process engineers decide how tightly each one needs to be held. The full chain is covered in our guide to ortho xylene uses and the phthalic anhydride feedstock route.

Matching the Safety Data Sheet

The SDS describes the substance, not the batch. Ours is Rev 3.1, dated 29 July 2026. Check that the product name and CAS number match the certificate. Physical properties in SDS section 9, such as a closed-cup flash point of 17 C, are public-reference values and were not measured on your batch. Transport is UN 1307, Class 3 flammable liquid.

Red flags on a certificate (general buyer guidance)

• Purity only. An assay with no impurity lines tells you little about what matters to a converter.
• No unit or basis. A bare percentage with no wt% or v/v marking cannot be compared.
• Every line exactly on its limit. This can mean the table was copied from the specification rather than measured.
• Mismatched identity. A different CAS number, a mixed xylene description, or an HSN code that does not fit. Ortho xylene is HSN 2902 41 00; mixed xylene has its own, different tariff line.
• Batch details that do not fit. Check that the batch number and date on the certificate are specific to the consignment, and compare against the producer's own certificate format.

If a CoA line fails or is missing (general guidance)

Do not unload on the assumption that it will be sorted out later. Keep the tanker and its paperwork as received, and note the failing or missing line, its unit and the TDS limit it breaches. Ask for a corrected or complete certificate, and if the result is in doubt, ask for a retest. Contact SPC with the batch number so the question can be traced to the right certificate. Your own quality procedure decides whether to hold, reject or accept the consignment.

Tanker-receipt checklist (general guidance)

This is general practice for a Class 3 flammable liquid, not an SPC procedure. Your own site safety rules come first.

1. Before the tanker arrives, confirm tankage is clean, compatible and has room for the volume, and that grounding and bonding points are ready.
2. Match the delivery documents to the order: product name, CAS 95-47-6 and UN 1307 on the paperwork.
3. Match the batch number on the CoA to the consignment before unloading.
4. Check the CoA results against the TDS limits using the method above, and compare against your own plant specification.
5. Take a retained sample at the point of receipt in line with your quality procedure.
6. Keep the CoA, TDS and SDS together with the receiving record.

What to send when you ask for a quote

Send your end use, expected monthly volume, delivery point and confirmation that you can receive a road tanker. We quote within 4 working hours, and a batch Certificate of Analysis is supplied with every delivery. See the ortho xylene product page for the full specification and downloads, and the related products phthalic anhydride and mixed xylene.