The case for a 99% purity floor

The research-peptide industry standard is ≥95% purity. Most reputable suppliers report 95–98% on their COAs. We chose to set Merit's release floor at 99%. Lots that don't clear it are rejected before shipping — documented in our internal lot history, but never reaching a customer. We want to lay out why we made that choice, what it costs, and why we think it's the right floor for the work researchers are doing.

Why 95% became the industry standard

95% purity is a reasonable historical default for research-grade peptides. It reflects what large-scale solid-phase synthesis (SPPS) can reliably produce without extensive downstream purification. Synthesizing a 30-amino-acid peptide involves 30 sequential coupling reactions, each with a typical efficiency of 99.5–99.9%. Even at 99.9% per step, a 30-residue peptide has only ~97% crude purity from the synthesis itself; longer peptides drop faster. Post-synthesis HPLC purification then concentrates the target peptide and removes truncations.

95% purity is what falls out of standard purification protocols. Pushing higher requires either (a) more aggressive purification gradients with substantial yield loss, or (b) multi-step purification with two or more separate HPLC runs. Both cost more and produce less peptide per gram of crude input.

What the 4-percentage-point gap actually represents

A 95% pure peptide contains 5% of "everything else." That "everything else" is mostly:

• Truncation products — peptides where one or more coupling reactions failed, producing shorter sequences.
• Deletion products — peptides missing a residue from the middle of the sequence.
• Oxidized forms — particularly relevant for sequences containing methionine or cysteine.
• Diastereomers — small fractions of epimerized residues.
• Residual solvents and reagents — usually below detection limits but technically present.

The clinical research literature using high-grade research peptides — Phase 2 and Phase 3 trials of tirzepatide, retatrutide, semaglutide — uses material at >99% purity. The peptides in those trials are released against pharmaceutical-grade specifications that explicitly require <1% total impurities.

Why this matters for sensitive research

For most in-vitro and many in-vivo research models, the difference between 95% and 99% peptide is small enough to be invisible. The target peptide is the dominant species; impurities are diluted enough to be irrelevant to most outcomes.

It stops being invisible when:

• The experimental endpoint is unusually sensitive — receptor binding assays at low concentrations, immunological readouts, dose-response work near the threshold.
• The peptide is administered repeatedly over weeks or months — impurity exposure compounds.
• Cross-reactivity with closely related sequences is a concern — truncation products of a longer peptide are often biologically active themselves.
• The work is intended to translate or compare with published clinical data — and that data used pharmaceutical-grade material.

For these cases, the 4 percentage points are doing real work. A 99% pure lot looks like the clinical reference material; a 95% pure lot has 5× the impurity load. The research model can't always tell you which difference matters.

What it costs to be at 99%

Three real costs:

1. Yield. Pushing purification past 98% typically discards 30–50% more crude material than stopping at 95%. The material doesn't disappear — it's collected as side fractions that aren't shipped — but the cost-per-shipped-gram goes up.
2. Lots rejected. A non-trivial fraction of crude lots come out of analytical testing between 95% and 99%. At our floor, those lots don't ship. We document them, we recover what we can, but they represent capital and time that produced no inventory.
3. Higher prices. Both of the above flow into per-vial cost. Merit's products are not the cheapest on the research-peptide market. They aren't supposed to be. The price reflects the floor.

Why we still think it's the right floor

Research peptide buyers fall into two categories. Some are running cell-based assays with broad tolerance — they probably could use 95% material and not see a difference. Others are running careful in-vivo work where small impurity profiles can move outcomes — and they need the cleaner material whether or not they ask for it. The second group is the population we want as customers.

Setting the floor at 99% means we don't have to ask "what is this lot going to be used for?" before deciding what to ship. The same lot is appropriate for both populations. We don't ship two grades; we ship one grade, calibrated to the higher-precision use case. The lower-precision researchers get a margin of safety they may not have known to ask for; the higher-precision researchers get the material they explicitly need.

That alignment — between what we ship and what the most demanding researcher would buy — is what 99% buys. The cost is real. The trade is, in our view, the right one.

This is an opinion piece reflecting Merit's quality position. It is not investment advice or regulatory guidance.