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Heavy metals: what "not detected" really means

"Not detected" means arsenic, cadmium, lead or mercury was below the method's detection limit, not that it was proven to be zero.

By Published Last updated 2 min read

Uses the lab reports of the 11 tested lots on this site

Part of an inductively coupled plasma mass spectrometer (ICP-MS) in a laboratory
Part of an inductively coupled plasma mass spectrometer (ICP-MS) in a laboratory. Photo: UCL Mathematical & Physical Sciences from London, UK, CC BY 2.0, via Wikimedia Commons

Key takeaways

  • Arsenic, cadmium, mercury and lead are the four Class 1 elements in the ICH guideline: toxic, with little or no use in making medicines.
  • "Not detected" means below the method's detection limit, not proven zero.
  • Every lot on this site was screened for all four, and none was detected.

"Not detected" is the result everyone wants to see. It has a precise meaning, and it is worth knowing it.

Why these four elements

The ICH guideline for elemental impurities puts arsenic (As), cadmium (Cd), mercury (Hg) and lead (Pb) in its Class 1. These are human toxicants with limited or no use in making medicines. When they appear, they usually come from commonly used materials, such as mined excipients[1]. The screen on BP's reports covers exactly these four.

What "not detected" means

Every method has a detection limit[2]. It is the lowest amount of a substance the method can detect, though not always measure as an exact value. "Not detected" means the amount was below that limit. It is a strong result, but it is not proof of zero, and its meaning depends on how low the method's limit is.

detection limitmeasurement123
  1. Noise: the small, random signal every instrument records even with nothing to find.
  2. A real signal: clearly above the noise and above the detection limit.
  3. The detection limit. A result below it is reported as not detected, which is not the same as zero.
Figure 1. What a detection limit is. Schematic drawn by BP after the ICH definition[2].

The results on this site

All 11 lots were screened for the four elements, and every result was not detected (Figure 2)[3]. On the reports, arsenic, cadmium and lead are listed in the results table and mercury in the comment line.

ProductAsCdPbHg
3P1TH4L0NLot EP-470NDNDNDND
6HK-CULot GH-692NDNDNDND
8PC Wolverine StackLot BT-317NDNDNDND
8PC-157Lot BP-482NDNDNDND
C1C-1295 + 1P4M0R3L1NLot CI-741NDNDNDND
M0TS-CLot MC-823NDNDNDND
R3T4Batch 2029/1NDNDNDND
S3L4NKLot SL-547NDNDNDND
S3M4XLot SM-381NDNDNDND
T1RZ3P4T1D3Batch 2029/1NDNDNDND
T3S4M0R3L1NLot TE-156NDNDNDND
Figure 2. Heavy metal screening for every lot on this site. ND: not detected. Data: Janoshik Analytical heavy metal reports in the COA library.

What to ask

For a demanding use, ask the lab or the supplier which method was used and what its detection limit is for each element. A "not detected" from a sensitive method says more than one from a coarse method.

Check it on real reports. The COA library has the full lab reports for 11 lots, with the original PDFs and links to the lab's own copies. Open the COA library

Sources

  1. ICH. Q3D(R2): Guideline for elemental impurities. Final version, adopted 26 April 2022. Section 4, element classes. database.ich.org (PDF)
  2. ICH. Q2(R2): Validation of analytical procedures. Final version, adopted 1 November 2023. Glossary: accuracy, intermediate precision, detection limit. database.ich.org (PDF)
  3. Bali Peptide Supply. COA library: every lab report for the lots sold on this site. Reports issued by Janoshik Analytical, with their task numbers, keys and original PDFs. balipeptidesupply.com/coa/

Each source was read in its own document on 16 Oct 2026. Numbers about BP's lots come from the reports in the COA library.

How this article was made

Written by Bali Peptide Supply from the sources listed above, each read in its own document on 16 Oct 2026. Every number about our lots comes from the Janoshik Analytical reports in the COA library, read by the site build, not typed by hand. The lead photo is from Wikimedia Commons under a free licence.

BP sells research materials for laboratory use only. This article explains laboratory testing and lab reports. It is not medical advice and not instructions for use.

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