L-Glutathione (Reduced, GSH) Testing & Verification
Independently verify what is actually in your L-Glutathione vial. KMD Analytical tests mail-in samples by RP-HPLC-UV against a certified reference standard and reports identity, chromatographic purity, and net-peptide content.
What L-Glutathione is
L-Glutathione is a naturally occurring antioxidant tripeptide composed of glutamate, cysteine, and glycine, with a molecular weight near 307 g/mol. Two structural features make it analytically distinctive: the glutamate is joined through an unusual gamma-glutamyl bond (not the standard alpha-peptide linkage), and the central cysteine carries a free thiol (-SH) group. That free thiol is readily oxidized, converting reduced glutathione (GSH) into its oxidized disulfide dimer (GSSG) — so the reduced-versus-oxidized state is central to what the material actually is. It has no aromatic residues and is detected by UV at 214 nm. Sold on the research and supplement market as a lyophilized powder, often in high-dose vials, its labeled identity and content are not independently guaranteed.
Why get your L-Glutathione independently tested
- Reduced (GSH) vs. oxidized (GSSG) integrity: the defining feature of reduced glutathione is its free thiol, which oxidizes on exposure to air, heat, and time to form the disulfide dimer GSSG. GSSG elutes as a distinct chromatographic peak, so an HPLC profile flags material that has partly oxidized away from the reduced form it claims to be.
- Net-peptide content vs. a high label mass: glutathione is frequently sold in large labeled amounts, but total vial mass includes counter-ion salt, residual water, and any bulking agent. A net-peptide assay reports the actual milligrams of glutathione present rather than total powder weight.
- Identity and substitution: as an inexpensive but high-volume compound, glutathione vials can be padded or mislabeled. Retention-time and UV-spectral matching against a certified reference standard confirms the vial contains glutathione and not a substitute.
- Related-substance impurities: synthesis and degradation can leave related peaks — including the oxidized dimer and other breakdown products. Chromatographic purity as area percent quantifies how much of the detectable material is the target compound versus everything else.
What we measure on L-Glutathione
Every L-Glutathione sample is analyzed by RP-HPLC with UV/diode-array detection at 214 nm against a certified reference standard — detection relies on the amide-bond absorbance because the tripeptide has no aromatic chromophore. The certificate reports three results: identity (retention-time and UV-spectral match to the reference), chromatographic purity as area percent of the main peak, and net-peptide assay as milligrams of peptide per vial. Where oxidized dimer (GSSG) is chromatographically resolved, it is reflected in the purity profile.
Every result is issued as a certificate of analysis you — or anyone you forward it to — can verify cryptographically. Reporting identity, purity, and milligram content is the point: a vial can be pure and still underfilled, so we report all three. More on purity vs. net-peptide content and how to read a peptide COA.
Our scope — stated plainly
Testing is by RP-HPLC-UV against a certified reference standard and confirms identity, chromatographic purity, and net-peptide content; it is not a thiol titration and does not include mass spectrometry, sterility, endotoxin, heavy-metal, or residual-solvent testing. L-Glutathione reference standards are commercially available, so identity testing does not usually require a sourcing delay. KMD Analytical is an independent laboratory.
KMD is an independent RP-HPLC-UV lab. We do not run LC-MS / mass-spec, sterility, endotoxin, or heavy-metal testing. If your job needs a capability we don't have, we'll say so.
L-Glutathione testing — FAQ
Can you tell whether my glutathione is the reduced form (GSH) or has oxidized to GSSG?
Our RP-HPLC-UV method resolves reduced glutathione from its oxidized disulfide dimer where the two are chromatographically separated, so the presence of GSSG shows up in the purity profile. Identity is matched against a certified reduced-glutathione reference standard. Note that this characterizes the compound chromatographically rather than by a dedicated thiol assay or mass spectrometry.
What does the net-peptide assay tell me that the label doesn't?
The number on a vial is usually the total powder mass, which includes counter-ion salt, residual water, and any bulking agent. Our net-peptide assay reports the actual milligrams of glutathione present, so you can see whether a vial genuinely contains close to its labeled amount.
Glutathione isn't a typical 'peptide' — can you still test it?
Yes. Glutathione is technically a tripeptide, and our RP-HPLC-UV method applies directly: we report identity against a certified reference standard, chromatographic purity as area percent, and content as milligrams per vial. We list it here because it is on our test menu.
Other peptides we test
Retatrutide · Cagrilintide · Tesamorelin · BPC-157 · see the full panel.