Peptide Testing

FOR LABORATORY RESEARCH USE ONLY

What each test measures, why it matters, and how to read a PureX Bio Certificate of Analysis.

LAST UPDATED · 29 JULY 2026

Every vial ships against a published, lot-specific Certificate of Analysis.

ON THIS PAGE

RELEASE SPECIFICATIONS

The release panel

The full panel at a glance. Each test is explained below. Testing varies by lot — review the lot-specific Certificate of Analysis for the exact tests and results that apply to the material you receive.

LC-MS

Compound confirmed

ICP-OES

Within limits

08pH

Is the material in range?

pH measurement

5.0 – 8.0

01 · PURITY

HPLC purity

What the headline percentage actually means

Reverse-phase high-performance liquid chromatography separates the components of a sample by how they interact with a C18 column, measured by a UV detector at 214 nm. The reported result is an area percentage — a result of 99.14% purity means the target compound accounted for 99.14% of the integrated chromatographic peak area.

The chromatogram itself is published with every lot. Look for labelled axes, a visible baseline, and clearly integrated, annotated peaks — not just the headline number.

RELEASE SPEC

≥ 98.0% of peak area

RP-HPLC

Area % · chromatogram published

RELEASE SPEC

Reported per lot, by mass

Quantitative analysis

Value printed on each COA

02 · QUANTITY

Potency (assay)

The number purity alone does not tell you

Purity describes the chromatographic profile. Peptide content describes how much of the lyophilised mass is actually peptide — the remainder is counter-ion, residual moisture, and other non-peptide mass associated with the finished material.

A material can test at ≥ 98.0% HPLC purity while having a lower peptide content. These results are not contradictory — they measure different things.

03 · IDENTITY

Identity verification (LC-MS)

Confirming identity

Purity tells you the sample is predominantly one component. It does not prove that component is the compound stated on the label. Mass spectrometry closes that gap by comparing the observed mass against the theoretical mass for the sequence.

An unconfirmed identity result fails release — regardless of its HPLC purity.

RELEASE SPEC

Labelled compound confirmed by LC-MS

Confirmed — releases

Not confirmed — fails, always

Three tests, three different questions

HPLC ASKS

How pure is the sample?

One dominant component in the chromatogram.

POTENCY ASKS

How many mg of peptide are in the vial?

Peptide as a share of total lyophilised mass.

MASS SPEC ASKS

Is it the right compound?

Observed mass matches the labelled sequence.

Only together do they verify a lot — which is why a PureX Bio COA reports all three.

CONTAMINATION & COMPOSITION

The rest of the panel

04 · Endotoxin

≤ 0.05 EU/mg

Endotoxins are lipopolysaccharides from Gram-negative bacteria. They persist after sterilisation and add variability to sensitive systems — so every applicable lot is screened with a kinetic LAL assay, and the measured result is published on its COA.

05 · Sterility

USP <71>

Applicable lots are assessed for viable microorganisms using USP <71> methodology. Sterile filtration reduces bioburden, but process controls are not finished-product testing — where performed, the result appears directly on the COA.

06 · Total yeast & mold

USP <61>/<62>

Microbial enumeration measures fungal bioburden in the finished lot rather than assuming it away. The result is reported on every certificate.

07 · Heavy metals

ICP-OES

Arsenic, cadmium, lead and mercury are measured individually against action limits by ICP-OES, with each analyte and its result printed on the certificate.

08pH

5.0 – 8.0

pH is measured and reported per lot. Many lots also carry water activity and residual solvent (GC-MS) results on the same certificate.

CERTIFICATE OF ANALYSIS

SPECIMEN

PX-[LOT]

[DD MMM YYYY]

SIX CHECKS, THIRTY SECONDS

Reading a Certificate of Analysis

1 · Match the lot number to the vial in hand. If they differ, stop and verify.

2 · Check the release date — specific to the lot, not reused across products.

3 · Look for both purity and potency — two numbers, two different questions.

4 · Confirm identity was tested — the labelled compound confirmed by LC-MS.

5 · Check endotoxin — a measured result, not just a pass mark.

6 · Review the chromatogram — labelled axes, visible baseline, annotated peaks.

Every released lot, searchable by lot number.

Testing is one part of the process

Quality Process

How a lot moves from documentation to release — and what fails it.

COA Library

Find your lot’s certificate and verify it before you buy.

Scientific Advisory

Who reviews our methods and specifications.

Every lot ships with its data.

Browse the catalogue, then verify the certificate before you buy.

FOR LABORATORY RESEARCH USE ONLY — NOT FOR HUMAN OR VETERINARY USE