A team at Hong Kong’s Government Laboratory has put out a validated, single-run method to identify and measure nine GLP-1 receptor agonists. It landed in the Journal of Chromatography A and it’s the kind of paper that ends up being more helpful than flashy, because GLP-1 receptor agonists have grown as a class faster than the everyday lab methods people rely on to distinguish one peptide from another.

Their panel covers bofanglutide, ecnoglutide, exenatide, liraglutide, mazdutide, retatrutide, semaglutide, survodutide, and tirzepatide. The authors stress how different these molecules are despite their family resemblance, spanning single-, dual-, and triple-agonist designs. They also point out why the list matters in practice: four are approved globally, two have recent approval from China’s National Medical Products Administration, and three are Phase III investigational candidates.

That spread is the whole rationale. Up to now, if a lab received a vial labelled with one of these names, there hasn’t been a single validated workflow that could, in one go, confirm which of the GLP-1 receptor agonists is actually in the sample.

Why GLP-1 receptor agonists are hard to tell apart

GLP-1 receptor agonists come from the same lineage and, for some pairs, share long sequence segments. The differences that matter pharmacologically can look small from an analytical angle: a swapped amino acid here, a fatty-acid chain length change there, a new receptor-targeting “arm” added on.

Relying on molecular weight doesn’t consistently solve it. Retention time alone won’t either, because closely related peptides can come off the column together. If you want confidence, you need accurate mass plus structural confirmation, and that’s the combination the paper tries to lock down.

This isn’t an abstract concern. A 2026 Frontiers in Pharmacology analysis looked at EudraVigilance reports tied to counterfeit semaglutide, and a 2024 Journal of Medical Internet Research market-surveillance study examined semaglutide sold online without a prescription. Different angles, same problem: product moves under a familiar name without independent verification of what it really is.

What the method actually does

For separation, they run an ACQUITY Premier BEH C18 column, 2.1 × 150 mm, 1.7 µm particles, at 50 °C. The mobile phases are water and acetonitrile, each with 0.1% difluoroacetic acid and 0.5% dimethyl sulfoxide, delivered at 0.3 mL/min using a multistep linear gradient. Most of the nine GLP-1 receptor agonists are reported as baseline-separated within a 20-minute run.

The key idea is a two-part MS strategy. A full-scan high-resolution MS gives accurate mass measurements, and data-dependent HRMS/MS adds fragmentation patterns to confirm structure. They take a top-down route, fragmenting the intact peptide directly rather than digesting it first.

That’s what pushes this past a quick screen. Accurate mass reduces the list of plausible candidates, but fragmentation is what pins down which peptide is present.

Validation performance, in the numbers

They report mass accuracy from 0.0 to 0.5 ppm, and fragment-ion coverage between 76% and 100% across the nine GLP-1 receptor agonists. Calibration behaved well, with r² ≥ 0.995 over 4 to 235 ng/mL.

Limits of detection are given as 0.44 to 2.06 ng/mL, with limits of quantitation at 8.29 to 11.74 ng/mL.

They then apply the method to marketed formulations of liraglutide, semaglutide, and tirzepatide using a “dilute-and-shoot” prep. Mean recoveries are reported at 113.7% to 118.4%. Those values are above 100%, and the abstract doesn’t say why, so anyone who needs that explained has to read beyond the abstract.

What it doesn’t cover

Three boundaries are worth being explicit about, because “validated” can sound broader than a single publication can really support.

First, they tested marketed pharmaceutical formulations, not research-grade powders, unknown-source material, or biological samples. How it behaves in those matrices is a separate issue.

Second, the method quantifies the nine GLP-1 receptor agonists they validated. Anything outside that list, a tenth agonist, a degradant, a synthesis-related impurity, isn’t something the paper proves it can handle. The authors call the approach flexible for current and next-generation GLP-1 receptor agonists, which is a statement about how they designed it, not a result established by validation.

Third, a recovery range of 113.7% to 118.4% is something to understand before leaning on it. It’s not a statistic to repeat uncritically just because it’s printed in an abstract.

Identity isn’t the same as purity

One of the quieter contributions of the paper is that it reinforces a distinction that supplier paperwork often blurs.

An identity test answers what the compound is. A purity test answers how much of the material is that compound versus other material. A certificate that lists a high purity percentage without clearly confirming identity has essentially answered the second question while assuming the first, and that assumption is exactly what breaks when something is mislabelled.

Here, the LC-HRMS approach for GLP-1 receptor agonists goes straight at identity via accurate mass plus fragmentation, and treats quantitation as its own track. As we have laid out elsewhere, purity testing and identity confirmation answer different questions, and a complete dataset needs both.

Why it matters for documentation

For labs buying or working with GLP-1 receptor agonists, this paper offers a concrete benchmark for what “good” documentation looks like.

It spells out the instrument conditions, the column and gradient, the mass accuracy, fragment coverage, working range, and detection limits. Those are the same details that separate a meaningful certificate of analysis from a single-line claim. When FDA evaluated seven research peptides for its compounding list in July, the common thread in the objections wasn’t primarily safety, it was the absence of impurity, aggregate, and endotoxin information in public sources or in the submitted documentation.

So for teams handling GLP-1 receptor agonists, it is worth understanding the analytical methods used in peptide characterisation before comparing suppliers, and our retatrutide reference material documentation covers the identity and purity fields discussed here. Retatrutide is one of the three investigational candidates included in the method, which makes it a practical example for reading a data package with a more skeptical eye.

References

The products referenced on this site are supplied for laboratory research use only. They are not medicines and are not intended for human or veterinary use. This article summarises published research for informational purposes and is not medical advice. Statements about third-party studies belong to their authors.

author-avatar

About Peptra Labs Research

The Peptra Labs research desk follows peptide science: new peer-reviewed studies, EU and US regulatory decisions, and clinical trial results. Every article cites its primary sources. All compounds discussed are for laboratory research use only.

Newer
Tirzepatide and Blood Pressure: 32 Trials, Two Signals
Back to list
Older MOTS-c and the Overlooked Microproteins: What a 2026 Review Adds

Related Posts