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Lab Testing & Purity

PT-141 Lab Testing & Purity Standards: HPLC, MS & Endotoxin

3 min read•Published 2025-09-09•Quality Peptide USA Research

PT-141 (Bremelanotide) is a synthetic 7-amino-acid cyclic analog of α-MSH and a non-selective agonist of the melanocortin receptors, with notable activity at MC3R and MC4R. It is studied in research models of central nervous system signaling and melanocortin pharmacology.. This guide covers lab testing & purity for PT-141 — written for laboratory researchers sourcing US-synthesized peptides from Quality Peptide USA.

Purity by Reverse-Phase HPLC

Every batch of PT-141 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 PT-141 product page.

Identity by Mass Spectrometry

PT-141 identity is confirmed by electrospray ionization (ESI) or MALDI-TOF mass spectrometry. The observed molecular ion is compared against the calculated mass (≈ 1025.18 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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