Heavy metals and elemental impurities testing

What did the older heavy metals test measure?

Lewen and colleagues describe the heavy metals test prescribed in the United States, British, Japanese and European pharmacopoeias as a wet chemical test ending in a visual, semi-quantitative comparison, and present an ICP-MS method as an alternative giving specific detection and quantitation for each element expected to respond in the compendial methods.^[5]

The elements they list are arsenic, selenium, cadmium, indium, tin, antimony, lead, bismuth, silver, palladium, platinum, mercury, molybdenum and ruthenium, and they state that ICP-MS removes the subjectiveness of the visual comparison.^[5]

Fischer and colleagues describe the newer USP, European Pharmacopoeia and ICH texts as ending the unspecific analysis of metals and metalloids outlined in USP <231> and EP 2.4.8. FDA states that, upon adoption of USP <232> and <233>, drug products and their components are not expected to demonstrate compliance with USP <231>, although USP may retain other specific metal limit tests, such as General Chapter <211> Arsenic, in particular monographs.^[6],[1]

How does ICH Q3D approach elemental impurities?

ICH Q3D(R2), published by FDA as guidance in September 2022, states that elemental impurities may be residual catalysts added intentionally in synthesis or may arise from interactions with processing equipment or container closure systems or from components of the product. It states that their levels should be controlled within acceptable limits.^[7]

The guidance has three parts: evaluation of toxicity data for potential elemental impurities, establishment of a permitted daily exposure (PDE) for each element of toxicological concern, and a risk-based approach to controlling elemental impurities in drug products. It defines the PDE as the maximum acceptable intake of an elemental impurity in pharmaceutical products per day.^[7]

PDEs are established for the oral, parenteral and inhalation routes, with cutaneous and transcutaneous values in an appendix. The stated scope includes drug products containing purified proteins and polypeptides and those containing synthetically produced polypeptides, but not drug products used during clinical research stages of development.^[7]

How are elements classified?

Class 1 comprises arsenic, cadmium, mercury and lead, which ICH Q3D describes as human toxicants with limited or no use in pharmaceutical manufacture whose presence typically comes from commonly used materials such as mined excipients. These four require evaluation across all potential sources and routes.^[7]

Class 2 elements are generally considered route-dependent human toxicants. Class 2A, cobalt, nickel and vanadium, has a relatively high probability of occurrence; Class 2B, silver, gold, iridium, osmium, palladium, platinum, rhodium, ruthenium, selenium and thallium, has a reduced probability and may be excluded unless intentionally added during manufacture.^[7]

Class 3, barium, chromium, copper, lithium, molybdenum, antimony and tin, has relatively low toxicity by the oral route but may need consideration for inhalation and parenteral products. Elements such as aluminium, boron, calcium, iron, potassium, magnesium, manganese, sodium, tungsten and zinc are not assigned PDEs in the guidance, owing to low inherent toxicity or differences in regional regulations.^[7]

How does a risk-based approach decide what is tested?

FDA's elemental impurities guidance summarizes the Q3D approach: identify known and potential sources, including intentionally added elements, elements in the materials used and elements introduced from manufacturing equipment or container closure systems, and then compare the observed or predicted level of each impurity with its PDE.^[1]

A control threshold is defined as 30 percent of the established PDE in the drug product. Where the evaluation does not show that a level is consistently below that threshold, additional controls, such as in-process controls or specifications for the product or its components, should be established.^[1],[7]

ICH Q3D states that it is not expected that all components will require testing for Class 1 elements, and that testing should be applied only when the risk evaluation identifies it as the appropriate control. FDA adds that USP <232> does not require routine testing of the finished product, and that testing could instead be performed on components such as the active ingredient and excipients.^[7],[1],[3]

Which analytical procedures are used?

ICH Q3D states that pharmacopoeial procedures or suitable alternative procedures should be used and that, unless otherwise justified, the test should be specific for each elemental impurity identified for control.^[7]

FDA's guidance states that USP <233> describes the procedures that ordinarily would be used and the criteria for acceptable procedures, and, for products without a USP monograph, recommends those procedures or, where they cannot be used, procedures that meet the validation requirements of <233>. A procedure used for routine testing must have its suitability verified under actual conditions of use.^[1],[4]

Fischer and colleagues write that substance-specific quantitative analysis and significantly lower detection limits require a changeover toward sensitive multi-element analysis by inductively coupled plasma atomic emission spectrometry (ICP-AES) and inductively coupled plasma mass spectrometry (ICP-MS).^[6]

A 2026 review by Galdino and César compares techniques, describing atomic absorption spectrometry as low-cost and sensitive but limited to single elements, ICP optical emission spectroscopy as robust and multielemental, ICP-MS as highly sensitive at ng/L levels but costly, and X-ray fluorescence as a rapid screening tool with limitations for quantification.^[8]

Limitations

PepGenex certificates of analysis do not report heavy metals or elemental impurities. This page describes the test category only.

A result from the older USP <231> test and a result from an element-specific procedure are not interchangeable: Lewen and colleagues describe the former as a visual, semi-quantitative comparison, and Fischer and colleagues describe it as unspecific.^[5],[6]

ICH Q3D PDEs are set per route for finished drug products within its scope. The guidance lists exclusions from its scope, among them elements intentionally included in a product and products used during clinical research stages.^[7]

The Galdino and César review was online ahead of print when read.^[8]

This page describes what the cited documents say. It is not a statement that any PepGenex material has been manufactured, tested or released under any of them.

Compound profiles

Research peptide profiles in this library. What this page describes applies to peptide lots in general; none of these profiles reports a result of it for any lot.

• Semaglutide research profile
• Tirzepatide research profile
• BPC-157 research profile

References

1. U.S. FDA. Elemental Impurities in Drug Products. Guidance for industry, August 2018. FDA docket FDA-2016-D-1692
2. United States Pharmacopeia, General Chapter <231> Heavy Metals (as named in FDA, Elemental Impurities in Drug Products, 2018). USP <231>
3. United States Pharmacopeia, General Chapter <232> Elemental Impurities—Limits (as named in FDA, Elemental Impurities in Drug Products, 2018). USP <232>
4. United States Pharmacopeia, General Chapter <233> Elemental Impurities—Procedures (as named in FDA, Elemental Impurities in Drug Products, 2018). USP <233>
5. Lewen N, Mathew S, Schenkenberger M, Raglione T. A rapid ICP-MS screen for heavy metals in pharmaceutical compounds. J Pharm Biomed Anal. 2004;35(4):739-752. PMID 15193718 · DOI 10.1016/j.jpba.2004.02.023
6. Fischer L, Zipfel B, Koellensperger G, et al. J Pharm Biomed Anal. 2014;95:121-129 (title withheld on this site; see the publication record). PMID 24667566 · DOI 10.1016/j.jpba.2014.02.016
7. ICH Q3D(R2) Elemental Impurities. U.S. FDA guidance for industry, September 2022. FDA docket FDA-2013-D-1156
8. Galdino JNS, César IDC. Comparison of analytical methods for the determination of elemental impurities in pharmaceutical products. Crit Rev Anal Chem. 2026:1-13 (online ahead of print). PMID 41848101 · DOI 10.1080/10408347.2026.2646284