Testing laboratories and test panels: accreditation, USP methods and screens

A test report is only as informative as the laboratory behind it and the tests it contains. Beyond purity and identity, some published reports for research peptides also list a panel: sterility, endotoxin, heavy metals, solvents and sometimes drug screens. This guide explains laboratory accreditation, the compendial methods behind each panel item, and the questions a reader can ask when a report looks incomplete. HPLC, mass spectrometry and net peptide content are covered in purity testing explained, and the basics of reading a report are in how to read a certificate of analysis. This page does not name or rank laboratories or sellers.

What ISO/IEC 17025 accreditation is

ISO/IEC 17025, first published in 1999, is the international standard for testing and calibration laboratories; it specifies general requirements for their competence, impartiality and consistent operation [1]. The edition in use is ISO/IEC 17025:2017, which FDA incorporates by reference in its rule on laboratory accreditation for food testing [2]. Accreditation is a third-party attestation that a laboratory conforms to the standard, and the standard is distinct from ISO 9001, the general quality management standard [1]. Accreditation bodies are assessed against a separate standard, ISO/IEC 17011; FDA's food-testing rule requires the accreditation bodies it recognizes to meet it [2].

Why the scope matters more than the logo

Accreditation is granted for particular methods. Under FDA's food-testing rule, for example, a laboratory must be accredited to ISO/IEC 17025 for each method it uses, and its scope of accreditation can be reduced or withdrawn [2]. A method that is not on a laboratory's scope is therefore not covered by its accreditation, even if the laboratory runs it. For that program FDA keeps a public registry of recognized accreditation bodies and accredited laboratories [2]; more generally, the accreditation body named on a certificate is where a method can be checked against the laboratory's scope.

Sterility: USP <71>

FDA describes USP chapter <71> "Sterility Tests" as the principal source for sterility test methods, including procedures and media [3]. Under cGMP, every batch of drug product purporting to be sterile or pyrogen-free must undergo appropriate laboratory testing to confirm it [4]. The test has known limits: FDA notes that the compendial sampling plan detects contamination in a lot where 10% of units are contaminated only about nine times out of ten [3]. In FDA's worked example, a 10,000-unit lot with 0.1% contamination tested with 20 units has a 98% chance of passing [3]. A sterility pass on a handful of vials is therefore weak evidence on its own, and FDA treats any positive result as a serious cGMP issue to be investigated [3]. Sterility and endotoxin are also separate questions: in a 2024 study of online semaglutide vials, the freeze-dried samples contained no viable microorganisms, yet endotoxin was detected in all of them [16].

Endotoxin: USP <85>

FDA updated its pyrogen and endotoxin questions-and-answers guidance as Edition 2 in March 2026, and it gives recommendations on the acceptance criteria in USP chapter <85> "Bacterial Endotoxins Test" [5]. The pharmacopoeial methods include gel-clot, turbidimetric and chromogenic techniques; the chromogenic technique measures colour released when a synthetic peptide-chromogen complex is cleaved [6]. Endotoxin limits are not fixed numbers per vial: for human products they derive from a threshold pyrogenic dose of 5 endotoxin units per kilogram of body weight, divided by the maximum dose per kilogram (the K/M calculation) [7]. A result reported only as "below" a limit per vial cannot be judged without knowing how that limit was derived [7].

Elemental impurities: USP <232> and <233>

USP <232> sets limits for elemental impurities in drug products, and its scope includes drug products containing synthetically produced polypeptides [8]. These impurities include catalysts and environmental contaminants and can be introduced by processing equipment or the container closure system [8]. Because arsenic, cadmium, lead and mercury are ubiquitous, at minimum these four must be considered [8]. Limits are expressed as permitted daily exposures that differ by route; the parenteral limit for inorganic mercury, for example, is one tenth of the oral limit [8]. USP <233> describes the measurement procedures, one using ICP-OES and one using ICP-MS, and a harmonized revision became official on 1 May 2026 [9].

Residual solvents and counterions

Residual solvents are classified and limited under ICH Q3C, which FDA has adopted as guidance [10]. Counterions are a separate line item: synthetic peptides are commonly obtained as TFA salts, and residual TFA can be quantified by FT-IR, 19F-NMR or HPLC with an evaporative light-scattering detector [11]. In one certified reference material, TFA accounted for nearly 25% of the mass [12]. The authors of the TFA study stress the importance of quantifying and specifying the counterion [11].

Why some reports include a fentanyl screen

Some sellers of research peptides publish a fentanyl screen alongside purity results. As of 22 October 2026, Amiravo has not found an FDA, DEA or USP document that calls for fentanyl testing of peptide products, or a regulator report of fentanyl detected in a research peptide. The compendial tests discussed above address sterility, endotoxin, elemental impurities and residual solvents [3, 5, 8, 10]. Any screen is only as informative as its method. Under ICH Q2(R2), the detection limit is the lowest amount of analyte that can be detected but not necessarily quantitated, and where one procedure cannot discriminate adequately, a combination of two or more is recommended [13]. A "not detected" line without the method, the analytes covered and the detection limit gives the reader little to evaluate [13].

Gaps seen in published test reports

The patterns below appear in publicly posted reports for research peptides. Each is framed as a question to ask, not as proof of a problem.

• Only a "date ordered." When was the sample received, when was it analyzed, and when was the report issued?
• No accreditation number. Which body accredits the laboratory, what is the certificate number, and is each method on the published scope [2]?
• No chromatogram or spectrum. Can the raw data be supplied? Specificity is demonstrated with data, for example by showing absence of interference or comparison with an orthogonal procedure [13].
• Measured content above the label amount. How was content measured, against which reference standard, and is the figure for peptide or for salt-containing powder [12]? In the semaglutide market study, content exceeded labeled amounts by 28.56% to 38.69% while purity was 7.7% to 14.37% [16].
• Panel names with "pass" but no numbers. What was the acceptance criterion, and what was the detection or quantitation limit? A specification consists of tests, references to procedures and acceptance criteria such as numerical limits [14, 13].
• Who commissioned the test. Was the sample chosen by the seller, and was it drawn from the lot being sold? Under cGMP, a drug maker may accept a supplier's report only if it runs at least one specific identity test itself and periodically validates the supplier's results [15].

Key points

• ISO/IEC 17025 sets requirements for laboratory competence and impartiality; accreditation applies to the methods listed on the scope [1, 2].
• USP <71> sterility testing has limited sensitivity because of small sample sizes [3].
• Endotoxin limits depend on dose and body weight, so a per-vial figure needs its basis [7].
• USP <232> covers synthetic polypeptides, and at minimum arsenic, cadmium, lead and mercury must be considered [8].
• No regulatory requirement for fentanyl screening of peptides was identified; a screen's value depends on its method and detection limit [13].