TDS, SDS and CoA

When you buy an extract, three documents come with it from the supplier. The TDS (technical data sheet) says what the product is. The SDS (safety data sheet) says how the product is to be moved and stored. The CoA (certificate of analysis) says what was measured in that batch. The three answer different questions, and the point most often confused is this: a number on the TDS is a limit, a number on the CoA is a measurement. The TDS says "linalool at least 25 %", the CoA says "linalool 31.2 %". They do not contradict each other: one is the limit, the other is the measurement for that batch. The figures are an example.

What do the three documents tell you?

The TDS is the permanent description of the product. It says which component should be present at which level and how that is measured. It also says what the product looks like, how long it keeps, how it is stored and where it is used. The numbers are lower or upper limits, such as "at least 25 %" or "at most 0.5 %". The document is not tied to a batch and stays the same as long as the product does not change. The product's INCI name (its cosmetic ingredient name) and CAS number (the substance's international identification number) are also given here.

The SDS is for transport, storage and emergencies. In the European Union its format is fixed by regulation: 16 sections, in the same order at every supplier [1]. The sections a buyer looks at most are 2 (hazard class and hazard pictograms), 7 (handling and storage, where handling means opening and decanting the drum), 9 (physical properties) and 14 (transport) [1]. The document is prepared by a competent person. The date of compilation is on the first page, and in a new version the changes are usually indicated in Section 16 [1]. One of its purposes is to let the employer see whether hazardous chemicals are present in the workplace and assess the risk to workers [1]. "MSDS" is the old name for the same document.

The CoA is the batch's report card. It comes separately with every batch. It carries the batch (lot) number, the production date and, for each measurement, the method name, the TDS limit and the value measured in that batch, side by side. The certificate is usually issued by the producer's own laboratory and signed by the responsible person. A measurement made by an outside laboratory comes as a separate report. As certificates accumulate, batch-to-batch variation becomes visible too. One drug development study collected the supplier certificates for three excipients accumulated over the years and read the batch-to-batch variation from those figures without running any experiments [2].

Which document answers which question?

How the solvent residue line is read is explained on a separate page: solvent residues.

What does "flammable" on the SDS mean?

The SDS describes the substance in its pure form, as it is in the drum. Essential oils and terpene (aroma compound) extracts give off a vapour that can ignite when warmed. The flash point is the lowest temperature at which the vapour above the liquid ignites from a spark, and it is given in Section 9 of the SDS [1]. In tea tree oil it is 56 to 60 °C, which places it in the flammable liquid class [3]. This is why most essential oils appear as "flammable liquid" on their safety data sheet.

The class describes behaviour in the warehouse, not the quality of the product. Once the class is set, the hazard pictogram, the signal word and the hazard statements in Section 2 follow from it [1]. The class says how the drum is to be stored: away from ignition sources, in a closed container, in a cool place. A finished product that contains the ingredient at one part in a thousand is assessed separately. The mixture's own hazard is given in Section 2 of its own data sheet [1].

How is a CoA read?

First, the limit and the result are read side by side. Each line should carry three things: the method name, the TDS limit and the value measured in this batch. If the measured value is within the limit, the batch conforms. A line that says "not detected" should also state the detection limit (the lowest level the instrument can see); without it the line says nothing.

The batch number should be the same in three places. The batch number on the certificate, the number on the package label and the number on the delivery note should match. The production date is read together with the shelf life on the TDS.

What does an accredited laboratory mean? It means the laboratory's measurement reliability has been audited by an independent body against an international standard (ISO/IEC 17025). If the certificate gives the laboratory's name and accreditation number, this can be verified.

A CoA does not replace the buyer's own check. The certificate is the supplier's measurement. US supplement manufacturing rules have the identity of a raw material confirmed by the buyer's own test, not by the supplier's certificate. The test can be as simple as odour and appearance [4]. The certificate is the starting point of the buyer's incoming inspection (the check made before accepting the goods). Which line is verified in the buyer's own laboratory is the buyer's choice.

Do the documents agree with each other, and are they current?

The identity lines should match. The product name and code, the CAS number and the INCI name should read the same on all three documents. The TDS limit and the CoA result should be in the same unit and by the same method. The component list in Section 3 of the SDS should not contradict the composition on the TDS.

The SDS date and Section 2 are read. Section 2 is read for the hazard class. A study that reviewed 42 safety data sheets in Indonesia found Section 2 complete in all of them and Section 11 (toxicological detail) complete in none [5]. The date of the sheet and the supplier that prepared it are checked as well.