What does 98 percent purity mean on a peptide COA?

It is an area figure by RP-HPLC at 220 nm: the main peak is at least 98.0 percent of the total UV-absorbing peak area, with any single related substance under 1.0 percent. It excludes water and counterion, which are measured separately.

What is the difference between purity and content?

Purity is how much of the peptide material is the target peptide (by HPLC area). Content is how many milligrams of peptide are in the vial (to within plus or minus 5 percent). A vial can be high purity and still hold water and counterion that are not peptide.

What does research use only mean?

The material is supplied for laboratory research only, not for human or animal consumption and not for diagnostic or therapeutic use.

A peptide wholesale glossary

The words a wholesale peptide certificate and price list use, in plain terms, tied to the limits we actually release a batch against.

Testing and the certificate

Certificate of analysis (COA)

The batch-specific record of what a lot was tested for and the results, against a written specification. Ours reports identity, purity, water, related substances, acetate, residual solvents, endotoxin where tested and peptide content, with the lot number and retest date. It is evidence for one batch, not a fitness-for-use claim. How to read one.

RP-HPLC purity (at 220 nm)

Reversed-phase high-performance liquid chromatography separates a sample into peaks; purity is the main peak's area as a percentage of the total UV-absorbing peak area, read at 220 nm where the peptide bond absorbs. Our limit is not less than 98.0 percent. It reflects the peptide against related impurities, not water or counterion, which are measured separately.

Mass spectrometry (identity)

Electrospray-ionisation mass spectrometry measures the intact molecular weight of the peptide. On the certificate it confirms identity: the observed mass must match the theoretical mass of the labelled sequence, backing up the HPLC retention time with proof the main peak is the intended molecule.

Water content (Karl Fischer)

A titration measuring residual water in the solid, as a weight percentage. Lyophilised peptides are hygroscopic, so water is a stability and a content concern; our limit is not more than 8.0 percent, reported separately from purity because water is mass in the vial that is not peptide.

Related substances

Impurities structurally related to the target peptide, such as deletion or truncation sequences and oxidised or deamidated forms, seen as the smaller peaks around the main peak in the HPLC run. Our limit is any single related substance not more than 1.0 percent.

Acetate content (counterion)

Synthetic peptides carry a net charge and are isolated as a salt with a counterion, commonly acetate. The counterion is not the peptide and is excluded from HPLC purity, but it is mass in the vial, so it is quantified separately; where supplied as the acetate our limit is not more than 15.0 percent.

Residual solvents

Volatile process chemicals left from synthesis and purification. Acetonitrile is limited to not more than 410 ppm and trifluoroacetic acid to not more than 1.0 percent, by gas and ion chromatography.

Endotoxin (LAL)

Lipopolysaccharides from Gram-negative bacteria, a contamination concern, detected by the Limulus amebocyte lysate assay and reported in endotoxin units. Where a line is tested, the result is stated on the certificate.

The product and the trade

Lyophilised

Freeze-dried: water is removed from the frozen peptide under vacuum, leaving a powder or cake far more stable in storage and transit than a solution. Our powdered lines are shipped and stored at minus 20 degrees Celsius and reconstituted before use.

Reconstitution

Dissolving the lyophilised powder back into liquid, with bacteriostatic or sterile water; add it gently, do not shake, and hold the result at 2 to 8 degrees Celsius. It is a handling step and does not change the tested purity or content. Storage and handling.

Bacteriostatic water

Sterile water with 0.9 percent benzyl alcohol as a preservative, used to reconstitute lyophilised powder; the preservative allows repeated withdrawals from a vial. It is a consumable, not an active, and is on the list as an ancillary line.

Batch / lot number

A batch is a quantity made in one run; the lot number is its unique identifier. Every certificate and result is tied to one lot, and the lot number on the vial must match the number on its certificate. Look one up.

Retest date

For a stable solid, the date by which a batch should be re-examined against specification to confirm it is still suitable, rather than a hard expiry. Ours reference a 24-month shelf from manufacture at minus 20 degrees Celsius.

Research use only (RUO)

Material supplied for laboratory research, not for diagnostic, therapeutic or human or animal use, labelled to that effect. It is the basis on which we supply. The position in full.

Wholesale and bulk

Both mean trade supply of finished, vialled, labelled units to trade accounts by the box; the difference is quantity and format, not product grade. Buying in bulk.

Minimum order value (MOV)

The order value that must be reached before an order is processed, measured on the goods before freight. Here it is $300.00, or $100.00 on a first order. The minimum.

Freight-included

The seller arranges and prices carriage, so the quoted price already covers shipping; here freight is included at or above $1,000.00, a flat $35.00 below. It is the opposite of EXW, where the buyer bears carriage from the seller's door.

Per-mg pricing

A vial's price relative to its labelled milligrams, so cost compares across vial sizes and suppliers like for like. It is only truly comparable read against the labelled content and the certificate, since purity, water and counterion vary. The catalogue by price per mg.