# Peptide Purity Testing: Methods, Costs, and How to Compare Third-Party Labs
URL slug: peptide-purity-testing-methods-costs-compare-labs
Meta description: Learn how peptide purity testing works, which analytical methods labs use, what it costs, and how to choose a reliable third-party lab for accurate results.
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## Why Peptide Purity Testing Matters
Whether you’re a researcher, analytical chemist, or laboratory manager, knowing the exact purity of a peptide compound is
non-negotiable. Impurities in peptide samples can include truncated sequences, deletion fragments, oxidized amino acids, residual solvents, and microbial contaminants — any of which can compromise experimental results or undermine data integrity.
Third-party purity testing adds an independent layer of verification that manufacturer certificates of analysis (CoAs) alone cannot provide. Understanding the available testing methods, realistic costs, and how to evaluate labs will help you make smarter sourcing decisions.
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## Common Peptide Purity Testing Methods
### High-Performance Liquid Chromatography (HPLC)
HPLC — particularly reversed-phase HPLC (RP-HPLC) — is the established standard for peptide purity assessment. The technique separates peptide components by hydrophobicity, producing a chromatogram that shows the percentage of the main compound versus impurities.
– **What it detects:** Truncated sequences, deletion peptides, aggregates, and residual reagents
– **Purity threshold:** Research-grade peptides typically require ≥98% purity by HPLC
– **Turnaround:** Usually 2–5 business days
### Mass Spectrometry (MS)
Mass spectrometry confirms the molecular identity of a peptide by measuring its mass-to-charge ratio. It is often paired with HPLC in an LC-MS workflow, offering both purity data and structural confirmation simultaneously.
– **What it detects:** Correct molecular weight, oxidation,
deamidation, and sequence variants
– **Best use:** Identity confirmation alongside HPLC purity percentage
### Amino Acid Analysis (AAA)
Amino acid analysis hydrolyzes the peptide into its individual amino acids and quantifies them chromatographically. This method verifies the correct composition and can provide accurate concentration data.
– **What it detects:** Incorrect amino acid ratios, missing residues – **Limitation:** Cannot detect sequence order errors; used as a complement to HPLC/MS
### Endotoxin and Sterility Testing
For research-grade peptide samples, endotoxin testing (Limulus Amebocyte Lysate or recombinant Factor C assays) and sterility testing are critical analytical checks beyond chemical purity assessment.
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## How Much Does Peptide Purity Testing Cost?
Costs vary based on the method, sample complexity, and lab. Here is a general breakdown:
| Test | Estimated Cost Per Sample |
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