From Benchmarking to Batch Release: Validating an RP-HPLC Method for GLP-1 Peptides on All-Carbon Microbeads
- Mar 6
- 6 min read
A validated, ICH Q2(R1)-compliant method for semaglutide and liraglutide — and what it means for pharmaceutical quality control.
The Gap Between a Good Column and a Validated Method
A chromatography column that separates peptides well is an important first demonstration. But a promising separation is not enough for a pharmaceutical laboratory. A method must be formally validated before it can be used for product release, stability testing, or in-process control. It must be shown to perform reliably, reproducibly, and consistently within defined acceptance criteria, in accordance with regulatory guidelines such as ICH Q2(R1) and USP <621>. This distinction matters more than it might initially seem.
A validated method carries a documented performance profile:
Defined linearity range
Known detection quantitation limits
Demonstrated precision across operators and days
Clear audit trail
Without that, analytical data cannot be used with confidence in a regulatory submission or a quality control (QC) decision.
Our previous ACS Omega publication established that NanoPak-C all-carbon microbeads can match silica C18 performance across a range of chromatographic metrics for GLP-1 peptides [1]. The question our new white paper answers is a different, more operationally significant one: can a method built on this stationary phase be formally validated to pharmaceutical QC standards?
The answer is yes — and the data are now documented.
Why GLP-1 Method Validation Is Harder Than It Looks?
Semaglutide and liraglutide are large, amphiphilic peptides with molecular weights above 3,000 Da and complex structural modifications — a C16 fatty acid chain in the case of liraglutide, and a C18 diacid linker in semaglutide. These modifications improve their half-lives in vivo but also make them chromatographically challenging. They interact strongly with reversed-phase media through both hydrophobic and non-specific mechanisms, and their retention behaviour is sensitive to subtle changes in pH, mobile phase composition, and temperature.
Validating an analytical method for these molecules requires demonstrating that the method is not just capable, but robust: that it will produce equivalent results when run on different days, by different analysts, using different column lots. This is the bar set by ICH Q2(R1), which specifies that a validated method must demonstrate linearity, precision (system precision and method repeatability), sensitivity (LOD and LOQ), and specificity under conditions representative of routine laboratory use.
Silica C18 columns have been used for GLP-1 analysis precisely because validated methods exist for them. Introducing a new stationary phase into a validated environment means starting that validation process from scratch — a meaningful investment for any laboratory. The white paper we have just published documents that investment for NanoPak-C all-carbon microbeads, providing a reusable validation foundation for laboratories considering this platform.
What the Validation Covered — and Why Each Parameter Matters?
The white paper reports validation data for both semaglutide and liraglutide across four core parameters. Rather than simply listing results, it is worth explaining what each parameter means practically for a QC or manufacturing team.
Linearity (R² > 0.99, 1.5–3.9 mg/mL)
Linearity tells you whether your detector response scales proportionally with concentration across your working range. For a release assay, the calibration range must bracket the expected product concentration with confidence. An R² of 0.99 or greater, demonstrated across 50–130% of the target concentration for both analytes, confirms that the method can accurately quantify samples at or near the assay concentration without requiring non-linear curve fitting or bracketing corrections.
Limits of Detection and Quantitation
The LOD (semaglutide: 0.0057 mg/mL; liraglutide: 0.0024 mg/mL) and LOQ (semaglutide: 0.019 mg/mL; liraglutide: 0.008 mg/mL) are both substantially below the lowest calibration point of 1.5 mg/mL. This headroom is not incidental — it means the method has the sensitivity to detect low-level related substances or degradation products at trace concentrations, which is important not just for main assay work but for monitoring product quality over time in stability studies.
Precision (%RSD < 2% across ten injections)
System precision is perhaps the most operationally critical parameter. A %RSD below 2% for peak area across ten consecutive injections demonstrates that the column and system are performing consistently — that there is no systematic drift, carry-over, or detector instability that would introduce uncertainty into quantitative results. In a QC environment, this figure underpins confidence in every single data point generated with the method.
Response Factor Consistency
Consistent peak area divided by concentration across injections confirms that the detector is responding proportionally and uniformly — an important check that the method is behaving as a reliable quantitative tool rather than generating variable signal for the same amount of analyte.
Liraglutide — Extending the Validated Platform to a Second GLP-1 Analogue
One of the most significant aspects of this white paper is the inclusion of liraglutide as a second validated analyte. Our ACS Omega publication focused on semaglutide [1]. Liraglutide is structurally distinct — it carries a single C16 fatty acid chain attached via a glutamic acid linker, compared to semaglutide’s more complex C18 diacid structure. Despite these differences, the same all-carbon stationary phase and mobile phase system (20 mM ammonium formate, pH 8.5, acetonitrile gradient) resolved and quantified liraglutide with equivalent performance: R² > 0.99, LOD of 0.0024 mg/mL, and %RSD below 2%.
This matters because it begins to establish that NanoPak-C all-carbon microbeads are not a single-molecule solution but a platform capable of supporting multiple GLP-1 programmes on the same validated analytical infrastructure. Laboratories running both semaglutide and liraglutide — or anticipating work on newer GLP-1 analogues — can potentially consolidate their analytical platform rather than maintaining separate validated methods on different column chemistries.
The pH 8.5 Mobile Phase — A Validation Choice, Not Just a Performance Choice
The mobile phase used in this validation — 20 mM ammonium formate buffer at pH 8.5 — deserves specific attention, because it illustrates one of the practical advantages of the all-carbon stationary phase beyond raw separation performance.
Most silica-based reversed-phase columns are validated at acidic pH (typically 0.1% TFA, pH ~2). This is not always the analytically optimal condition — it is often the condition that silica can tolerate. Running silica C18 at pH 8.5 leads to progressive silica dissolution and bonded-phase hydrolysis, shortening column lifetime and introducing retention-time drift that can invalidate a method or require frequent recalibration.
By validating at pH 8.5 on an all-carbon stationary phase that is chemically stable from pH 1 to 13, this white paper demonstrates something qualitatively different: that the method has been designed around the optimal chemistry for the analyte, rather than around the limitations of the column material. Ammonium formate at pH 8.5 reduces the strong ion-pairing effects of TFA, improves peak shape for fatty acid-modified peptides, and allows subtle charge-based differentiation between closely related species — all without the column degradation risk that would make such conditions impractical on silica.
For QC laboratories that currently use acidic conditions because that is what their silica columns tolerate, this represents a genuinely different conceptual approach to method development: start with the chemistry the molecule needs, then choose a stationary phase that can sustain it.
From Validated Method to Transfer-Ready Protocol
Method validation is not the endpoint — it is the prerequisite for method transfer. A validated method, by definition, has documented performance characteristics that a receiving laboratory can verify independently. The data in this white paper provide exactly that foundation: a defined mobile phase system, column format (150 mm × 4.6 mm, 5 µm), flow rate (0.6 mL/min), detection wavelength (214 nm), and acceptance criteria (%RSD < 2%, R² > 0.99) that can be replicated on a Shimadzu LC2050C or equivalent HPLC platform.
For organisations with multiple sites — development, QC, and manufacturing — this matters considerably. Method transfer failures are a common source of deviation reports and delayed batch releases. Having a validated method with clear, quantitative acceptance criteria reduces the ambiguity that causes transfer failures. A stationary phase that does not degrade under the operating conditions means that column-to-column variability is one fewer variable to manage during the transfer process.
What This Means for Regulatory Submissions?
ICH Q2(R1) compliance is not just a quality standard — it is a regulatory expectation. Analytical methods used to support drug applications must be validated to ICH Q2(R1) standards, and the validation data must be included in the relevant sections of CTD submissions (Module 3, Section 3.2.P.5.2 for analytical procedures and validation). The white paper documents the validation in a format and with the parameters required to support that submission.
This does not mean the data can be inserted directly into a submission without further laboratory-specific verification — every site and every regulatory authority will have its own requirements. But it does mean that a laboratory adopting this method is starting from a validated, documented foundation rather than from first principles, which significantly reduces the analytical development burden.
Read the White Paper
The full validation data, chromatograms, linearity plots, and precision overlays are available in our white paper: https://896777ce-f42d-4b7a-bd02-a140835c79ad.filesusr.com/ugd/c94fdf_9c27af1ff3714c7ab530c6005dc45d49.pdf.
If you are interested in evaluating NanoPak-C all-carbon microbeads for a GLP-1 analytical or manufacturing programme, or if you would like to discuss method transfer, column formats, or application-specific support, please contact our technical team at inquiry@millennialscientific.com, call us at 855 388 2800, or fill in our online contact form at www.millennialscientific.com/contact.
Reference
1) Michael Jack Parente, Balaji Sitharaman, Liquid Chromatography Evaluation of a Novel Graphitic Carbon Stationary Phase Using Glucagon-Like Peptide-1 Analogs, ACS Omega, 2025. https://pubs.acs.org/doi/10.1021/acsomega.5c02172
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