Peptide testing glossary

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Terms

Bacteriostatic water

Sterile water with a preservative added, so the vial can be opened more than once. More

Batch number (lot number)

The code a manufacturer gives one production run. A certificate is useful only if its batch number matches the vial you have. More

Benzyl alcohol

The preservative in bacteriostatic water, usually at 0.9%. It stops bacteria multiplying after the vial is opened. More

Certificate of analysis (COA)

The document that reports what a laboratory measured in a sample. It is evidence only if it can be checked with whoever issued it. More

Chromatogram

The graph an HPLC run produces. Each peak is a substance leaving the column; the size of a peak shows how much of the material it represents. More

Conforms

A result that sits inside the specification it was judged against. A result outside it is reported as out of specification.

Content (net peptide content)

How many milligrams of the compound are in the vial, measured against a reference standard. This is the result that catches under-filled vials. More

Declared content

The amount the label says is in the vial, for example 10 mg. A report prints it next to the measured content so the two can be compared.

E. coli

A bacterium whose presence points to contamination during manufacture or filling. The Veritalys full panel tests for it specifically. More

Endotoxin

Debris from the outer wall of certain bacteria. It is not alive, survives sterilisation and passes through filters, so a sterile vial can still carry it. More

EU per vial

Endotoxin units in the whole vial. A number like this is a measurement; the word negative is a judgement against a limit you may not see. More

Freeze-dried (lyophilised)

Powder made by freezing a solution and removing the water under vacuum. It is the stable form of most research peptides and the form to post for testing.

HPLC (high performance liquid chromatography)

The method that separates a sample into its parts so each can be measured. It gives the purity percentage and, against a reference standard, the content. More

Identity

Whether the vial holds the compound it claims to. The sample is run next to a known-pure reference standard of that compound, and the two have to match. More

LAL assay

The standard test for bacterial endotoxin, named after the horseshoe crab blood extract it uses. A quantitative LAL test reports a number, not just a yes or no. More

Peak area

The size of one peak on a chromatogram. Purity is the main peak's area as a share of all the peaks the detector saw.

pH

How acidic or alkaline a liquid is, on a scale from 0 to 14, with 7 as neutral. More

Purity

The share of the detected material that is the compound, as a percentage of total peak area. It cannot tell you how much is in the vial. More

Reference standard

A known-pure sample of a compound. Identity and content are measured by comparing your sample with it, which is why you must say which compound you are sending.

Report number

The permanent number on every Veritalys certificate: VT- followed by 7 letters and digits. Anyone holding it can open the record on the verify page. More

Retention time

How long a substance takes to pass through the HPLC column, in minutes. The main peak of your sample should appear at the same time as the reference standard.

Salmonella

A bacterium tested for on its own in the Veritalys full panel, because a specific test can find it even when the general counts look normal. More

Specification

The acceptance limit a result is judged against. Conforms means the result is inside it.

Sterility

Whether anything living grows from a sample when it is cultured. It says nothing about endotoxin, which is not alive. More

TAMC (total aerobic microbial count)

The number of bacteria that grow in air from a sample. Part of the Veritalys full panel. More

TYMC (total yeast and mould count)

The number of yeasts and moulds that grow from a sample. Part of the Veritalys full panel. More

Where to go next

The guides explain the ideas behind these terms in more depth. The price list shows what each test costs for every compound, and the verify page opens any Veritalys report by its number.