Citric acid is citric acid. The molecule does not change between grades. What changes is everything around it: how much of the material is the molecule, what else is present, how finely it is milled, and what the producer is prepared to certify about it.
That distinction is why ordering by chemical name alone is the single most common cause of a material arriving that cannot be used.
What grade actually controls
- Assay. The proportion that is the named substance. Food and pharmaceutical grades are typically held to a tighter range than technical grade.
- Impurity limits. The important part. Food and pharma grades carry defined limits on heavy metals, arsenic, and residues relevant to that use. Technical grade often does not set them at all — not because the material is dangerous, but because nobody testing it was asked the question.
- Physical form. Particle size, bulk density and whether the material is granular, fine powder or prilled. This is not cosmetic; it governs dissolution rate, dosing accuracy and how the material behaves in a dry blend.
- Documentation. A food or pharma grade should come with a certificate of analysis referencing a recognised monograph. Technical grade may come with far less.
Why substitution goes wrong
The failure is rarely dramatic. More often it is a batch that dissolves too slowly and throws out a continuous process, a powder that cakes in the hopper because the moisture spec was looser than expected, or a finished product that fails an audit because the intake paperwork does not reference the right standard.
The reverse also happens: buying pharmaceutical grade for an application that only needs technical, and paying a premium for a specification nobody downstream will ever ask about.
Specify by monograph where one exists
For many food additives there is a recognised standard — FCC for food chemicals, USP or BP for pharmaceutical use, and the E-number framework for additives sold into food in many markets. Naming the standard on the purchase order removes most of the ambiguity in one line.
“Citric acid” is an invitation to interpretation. “Citric acid monohydrate, food grade, FCC, fine granular” is an order.
What to put on the enquiry
- Chemical name and CAS number. The CAS number removes any doubt about which compound and which hydration state you mean — monohydrate and anhydrous are different materials with different dosing.
- Grade and standard. Food, pharma, feed or technical, and the monograph if your process references one.
- Physical form. Powder, granular, flake or prill, with a mesh range if it matters.
- Quantity and packing. Including whether you need a specific pack size to suit your handling.
- Destination market. Permitted additives and declaration rules differ, and this affects what can be supplied.
Check the arriving material against it
When the consignment lands, read the certificate of analysis against the specification you ordered to — not against the last certificate you filed. Appearance and assay are the two fields that catch a grade substitution fastest. Our note on reading a certificate of analysis covers what each field is telling you.
Every product in our catalogue lists its CAS number, appearance and solubility so you can check the basics before you enquire. Send us your house specification with the enquiry and we will check the producer’s specification against it before the order is placed.