Lab Testing & Purity
L-Glutathione Lab Testing & Purity Standards: HPLC, MS & Endotoxin
3 min read•Published 2025-09-21•Quality Peptide USA Research
L-Glutathione (reduced form, GSH) is a naturally occurring tripeptide composed of glutamate, cysteine, and glycine. It is the most abundant intracellular antioxidant in mammalian cells and is widely used in oxidative-stress, detoxification, and redox-biology research.. This guide covers lab testing & purity for L-Glutathione — written for laboratory researchers sourcing US-synthesized peptides from Quality Peptide USA.
Purity by Reverse-Phase HPLC
Every batch of L-Glutathione is analyzed by reverse-phase HPLC using a C18 stationary phase and a water/acetonitrile gradient with 0.1% TFA. The release specification is ≥ 99% purity by area-under-curve at 220 nm. The chromatogram is included in the full certificate of analysis PDF available on the L-Glutathione product page.
Identity by Mass Spectrometry
L-Glutathione identity is confirmed by electrospray ionization (ESI) or MALDI-TOF mass spectrometry. The observed molecular ion is compared against the calculated mass (≈ 307.32 g/mol) and must match within 1 Da to pass release. Sequence-level confirmation is performed on representative lots through MS/MS fragmentation.
Endotoxin and Bioburden
Every batch is screened with the Limulus Amebocyte Lysate (LAL) assay. Release specification: < 0.10 EU/mg. Bioburden is verified by membrane filtration with target < 1 CFU per vial. These thresholds matter for cell-culture work where endotoxin contamination confounds inflammatory and proliferation readouts.
Water Content and Residual Solvents
Karl Fischer titration verifies water content below 5%, ensuring the lyophilized cake is fully dry. Residual organic solvent screening (gas chromatography) confirms acetonitrile and TFA residuals are within USP <467> Class 3 limits. This is one of the most overlooked QC steps when sourcing peptides from overseas suppliers — but it directly influences downstream cell viability.
Research Use Only
All content is for laboratory and in-vitro research contexts only. Not intended to diagnose, treat, or prevent any condition. Not for human or veterinary consumption.
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