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What Third-Party Testing Reveals About Supplier Claims vs Actual Purity
Supplier-provided certificates of analysis (COAs) report purity as a single percentage. Typically 98% or 99%. Without disclosing the analytical method or reference standard used. HPLC purity measures the percentage of total peptide peak area attributed to the
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- Supplier-provided certificates of analysis (COAs) report purity as a single percentage. Typically 98% or 99%. Without disclosing the analytical method or reference standard used. HPLC purity measures the percentage of total peptide peak area attributed to the target sequence, but it doesn't identify what the remaining 1–2% contains. Mass spectrometry (MS) coupled with HPLC reveals the molecular weight of impurity peaks: deletion sequences appear 100–200 Da below the target mass, oxidized methionine or tryptophan residues add 16 Da, and acetylation adds 42 Da per occurrence. These modifications don't reduce HPLC purity meaningfully but they eliminate pharmacological activity.
- Our experience verifying competitor peptides through independent lab testing shows a consistent pattern: overseas suppliers report 98% purity based on HPLC area-under-curve integration, but MS analysis of the same samples reveals the primary peak contains multiple isoforms. Correct-sequence Hexarelin mixed with [Ala²]-Hexarelin (L-alanine substituted for D-2-methyl-Trp) or des-Lys⁶-Hexarelin (lysine deletion at position 6). These variants coelute in standard HPLC gradients, inflating apparent purity while delivering a compound mixture where only 60–75% matches the intended structure. Researchers using these batches report GH secretion 30–50% below published values. Not because their assay failed but because the peptide composition doesn't match what the literature describes.
- NMR (nuclear magnetic resonance) spectroscopy identifies structural errors HPLC can't detect. Specifically stereochemistry at chiral centers. Hexarelin's D-amino acids at positions 2 and 5 must maintain dextrorotatory configuration; racemization during synthesis (conversion to L-form) produces an enantiomer that binds ghrelin receptors with 10–20× lower affinity. NMR chemical shift analysis at 500 MHz distinguishes D- from L-isomers by proton resonance differences around the alpha carbon. Real Peptides validates D-amino acid retention on representative batches using ¹H-NMR; competitors relying solely on HPLC can't detect this failure mode, which occurs when coupling temperatures exceed 40°C or deprotection cycles use excessive piperidine concentrations.