The global peptide manufacturing industry is facing renewed scrutiny following reports of serious quality-control deficiencies at overseas production facilities and scientific findings involving online peptide products.
An October 2026 report by Bloomberg, carried by the Los Angeles Times, detailed FDA inspection findings at two Chinese facilities associated with the manufacture of ingredients used in compounded GLP-1 products.
Separately, peer-reviewed research published in the Journal of Medical Internet Research documented substantial discrepancies between advertised product claims and measured semaglutide composition in samples purchased from certain online sellers.
Together, these findings raise an important analytical question: is a certificate of analysis reporting 99% peptide purity sufficient to establish the overall quality of a peptide material?
From an analytical chemistry perspective, the answer is no.
A purity percentage represents one measurement within a broader framework of material characterization. Identity, chromatographic purity, quantitative content, impurity profiles, and contamination-related attributes each provide different information. Understanding these distinctions is essential for laboratories, manufacturers, and research organizations responsible for evaluating peptide materials.
Recent FDA inspection findings highlight manufacturing quality concerns
In October 2026, Bloomberg reporting described FDA inspection findings involving two Chinese manufacturers associated with GLP-1 active ingredients. The reported deficiencies included contamination concerns, inadequate manufacturing documentation, and problems involving supplier verification.
At one facility, inspectors documented black mold on equipment, contamination on floors, and concerns involving the handling of records and samples. At another, investigators identified problems involving the verification and documentation of ingredients obtained from other manufacturers. The FDA placed the companies on import-alert lists, allowing affected shipments to be detained.
These findings illustrate the importance of effective manufacturing controls, traceable documentation, and appropriate quality oversight.
However, the findings concern specific inspected facilities and should not be generalized to every manufacturer operating in China. They also do not establish that Chinese manufacturers have adopted a coordinated policy to reduce peptide purity standards.
Published research raises questions about advertised 99% purity claims
A 2024 peer-reviewed study in the Journal of Medical Internet Research examined semaglutide products purchased from online sellers operating without prescription requirements. Researchers analyzed the products' chemical composition and other quality-related characteristics.
Three lyophilized semaglutide samples were obtained for laboratory evaluation. Although the products were advertised with approximately 99% purity claims, researchers reported that semaglutide represented only 7.7% to 14.37% of the total lyophilized powder mass.
The researchers also found that measured semaglutide quantities exceeded the labeled amounts by approximately 29% to 39%. Endotoxin was detected in all three samples.
These findings highlight why analytical quality cannot be established through a single purity claim.
An essential scientific distinction
The study's low percentage values should not be interpreted as equivalent to HPLC chromatographic peak-area purity.
The researchers measured semaglutide as a proportion of total powder mass, while chromatographic purity commonly expresses the relative detector response attributable to the principal peptide peak. The study did not identify peptide-like impurities in its chromatographic assessment.
This distinction is especially important because lyophilized materials may contain excipients and other constituents that contribute to total powder mass without appearing as peptide-related impurity peaks.
What does 99% HPLC peptide purity actually measure?
High-Performance Liquid Chromatography is widely used to separate and evaluate components within peptide samples. In a typical reversed-phase HPLC analysis, compounds are separated based on their interactions with the chromatographic system. A UV detector measures the response of components as they elute from the column, and the resulting chromatogram contains peaks corresponding to detected components.
Under a common area-normalization method, the principal peptide peak area is compared with the total area of included peaks. For example, if the principal peptide accounts for 99% of the integrated chromatographic response, the sample may be reported as having 99% HPLC area purity.
However, this result does not necessarily establish that the peptide represents 99% of the total material mass. HPLC area purity can also be influenced by chromatographic selectivity, detector response, integration parameters, and the ability of the method to resolve relevant impurities. The analytical method and supporting chromatographic data are therefore essential to interpreting the reported value.
Identity, purity and net peptide content are different measurements
One of the most common sources of confusion in peptide analysis is treating identity, purity, and content as interchangeable measurements. They are not.
| Analytical measurement | What it evaluates |
|---|---|
| Peptide identity | Whether the expected peptide is present |
| Chromatographic purity | The relative contribution of the principal peptide peak under the specified method |
| Net peptide content | The measured quantity of target peptide in the sample |
| Endotoxin testing | The presence or quantity of bacterial endotoxins |
| Moisture testing | Water content within the material |
A sample can demonstrate the expected peptide identity while containing less target peptide than stated on its label. Similarly, a sample can demonstrate high chromatographic purity while containing significant quantities of water or excipients.
An apparently satisfactory result in one analytical category does not establish compliance with specifications for other quality attributes.
Why this matters for laboratory testing
Analytical laboratories must select methods appropriate to the specific questions being investigated. Mass spectrometry may support peptide identity verification. HPLC may be used to evaluate chromatographic purity. A suitably validated quantitative method may establish peptide content. Endotoxin and moisture measurements require additional methods designed for those specific attributes.
These techniques provide complementary information rather than interchangeable results.
Why different laboratories may report different peptide purity results
Discrepancies between independent laboratory reports are another important consideration. Two laboratories may evaluate samples from the same nominal manufacturing lot and report different purity percentages. Potential contributing factors include:
- Chromatographic column chemistry
- Mobile-phase composition
- Gradient conditions
- UV detection wavelength
- Peak resolution
- Integration parameters
- Sample preparation
- Storage and transportation conditions
- Actual differences between submitted samples
For example, one chromatographic method may resolve an impurity that partially overlaps the principal peptide peak under another method. This can produce different reported area-purity percentages.
However, a lower result should not automatically be attributed to better analytical resolution. The discrepancy may also indicate sample degradation, material inconsistency, or an analytical problem. The appropriate response is a documented scientific investigation.
The role of independent analytical testing
Independent laboratory testing can provide valuable information about the characteristics of peptide materials. However, independence alone does not establish analytical accuracy.
The reliability of testing depends on method suitability, instrument performance, qualified personnel, sample integrity, and appropriate data interpretation.
When evaluating conflicting results, laboratories and research organizations should review the underlying analytical evidence. This may include chromatograms, peak integration tables, sample identifiers, calibration records, system suitability data, and analytical procedures. Where appropriate, complementary techniques may help characterize unidentified components or resolve uncertainty.
Independent testing is most useful when it produces defensible analytical data rather than simply another numerical result.
Why certificates of analysis require scientific interpretation
A certificate of analysis summarizes results obtained for a particular sample or batch under specified analytical conditions. However, a COA should not be interpreted as a universal guarantee of product quality.
Its significance depends on the sampling process, the analytical methods employed, the quality of the supporting records, and the specifications against which results are evaluated.
A comprehensive evaluation may require more than one analytical technique. For example, a high HPLC area-purity result does not independently establish sterility, endotoxin compliance, accurate peptide content, or absence of non-UV-active contaminants. Likewise, mass confirmation alone does not establish chromatographic purity.
Scientific interpretation requires understanding what each test can and cannot demonstrate.
A scientific framework for investigating peptide quality discrepancies
When analytical results differ materially, a structured investigation may include the following steps.
- Verify sample identity and traceability. Confirm that samples correspond to the intended manufacturing lot and review available chain-of-custody documentation.
- Compare analytical methodologies. Examine chromatographic conditions, detection parameters, sample preparation, and method suitability.
- Review chromatographic evidence. Evaluate peak separation, integration practices, unexpected signals, and relevant system suitability information.
- Assess analytical variability. Determine whether the observed difference is consistent with established method precision and measurement uncertainty.
- Consider complementary analytical methods. Use additional techniques where appropriate to characterize impurities or verify quantitative results.
- Document the investigation. Record findings, unresolved questions, and scientifically justified conclusions.
The objective is not to select the most favorable reported value. It is to determine which conclusions are supported by the available evidence.
Sycamore Analytical: advancing clarity in peptide characterization
At Sycamore Analytical, our mission is to support research organizations through scientifically grounded analytical evaluation and clear interpretation of laboratory data. Our focus includes peptide identity, chromatographic purity, and quantitative peptide-content analysis.
We recognize that the reliability of analytical results depends on more than a certificate displaying a percentage. Appropriate analytical methods, sample documentation, and transparent reporting are central to meaningful material characterization.
As the peptide industry faces greater scrutiny, laboratories have an important role in helping research organizations understand analytical results and investigate unexpected findings.
Our guiding principle is straightforward: meaningful analytical testing should produce defensible scientific information, not merely favorable numbers.
Frequently asked questions
Does 99% HPLC purity mean a vial contains 99% peptide by weight?
No. HPLC area purity and mass-based peptide content are different measurements.
Can a peptide have high purity but inaccurate content?
Yes. A material may demonstrate high chromatographic area purity while containing more or less target peptide than its stated quantity.
Does HPLC purity testing detect bacterial endotoxins?
Not through routine HPLC-UV peptide purity analysis. Endotoxin evaluation requires a suitable separate analytical method.
Why can two laboratories report different purity results?
Differences in chromatographic separation, detection, integration, sample preparation, and actual sample composition can influence reported values.
Can mass spectrometry confirm peptide purity?
Mass spectrometry can provide important information about identity and impurities. However, a mass spectrum alone does not necessarily establish a validated quantitative purity value.
Does a certificate of analysis establish overall material quality?
Not by itself. A COA documents specified test results and must be interpreted in relation to the analytical methods, sampling process, specifications, and intended application.
Conclusion: analytical quality requires more than a purity percentage
Recent manufacturing investigations and scientific research demonstrate why peptide quality evaluation requires a broader analytical perspective.
A reported 99% purity value may provide useful information, but it does not independently establish identity, quantitative content, manufacturing integrity, or freedom from contamination.
Meaningful analytical characterization depends on appropriate methods, reliable documentation, and scientifically justified interpretation. For laboratories, manufacturers, and research organizations, the objective should be analytical confidence supported by evidence.
Because in analytical science, understanding the result is just as important as reporting it.
Scientific references
- Edney A. Compound Semaglutide, Tirzepatide Plants in China Found With Black Mold by FDA. Bloomberg, 15 October 2026; carried by the Los Angeles Times, 19 October 2026.
- Ashraf AR, Mackey TK, Vida RG, Kulcsár G, Schmidt J, Balázs O, Domián BM, Li J, Csákó I, Fittler A. Multifactor Quality and Safety Analysis of Semaglutide Products Sold by Online Sellers Without a Prescription: Market Surveillance, Content Analysis, and Product Purchase Evaluation Study. Journal of Medical Internet Research. 2024;26:e65440.
- U.S. Food and Drug Administration. Q2(R2) Validation of Analytical Procedures.
- U.S. Food and Drug Administration. Q14 Analytical Procedure Development.
- United States Pharmacopeia. General Chapter <621>: Chromatography.
Scientific and regulatory notice. This article is intended for scientific and educational purposes. It does not constitute certification of any particular product, manufacturer, or analytical laboratory. References to regulatory guidance do not imply FDA approval, accreditation, or regulatory endorsement of Sycamore Analytical. Analytical capabilities and service availability should be confirmed directly with the laboratory.