A chemical signal can be misleading
Cannabis testing technology improves knowledge of what a sample contains by separating chemicals, identifying them and measuring their concentrations. One practical advance is the ability to recognise when a signal attributed to THC also contains a contribution from another substance. This matters because a reported concentration can influence product labelling, research conclusions and regulatory classification. Precision on a printed certificate is useful only when the underlying signal represents the intended compound.
The interference found in 2025
A 2025 NIST study identified interference from cannabinolic acid, or CBNA, and by-products associated with synthetic delta-8 THC. These substances could overlap the signal used to measure delta-9 THC and make its concentration appear higher. The researchers examined 16 commercial hemp samples and 20 seized cannabis samples, and used records from 7,448 plant samples analysed in 2023 to investigate the problem in a larger population. Under the US classification system, such errors could cause hemp to be classified as marijuana.
Separating overlapping peaks
Chromatography produces a pattern of signals as components pass through an analytical system. Two substances that appear too close together can be counted as one unless the method distinguishes them. The NIST paper described improved separation, more selective detection and mathematical separation of overlapping peaks as ways to resolve interference. These approaches address a specific source of measurement error. The important result is a concentration more closely tied to the substance being measured, especially when small differences affect a classification.
A shared reference for laboratories
NIST released Hemp Plant Reference Material RM 8210 in July 2024. Laboratories can analyse this material and compare their results with its assigned information for cannabinoids and toxic elements. A reference material supplies a common point of comparison: an unexpected result can reveal a problem in the measurement process before it carries into reports on other samples. It also connects the instrument to a physical material resembling the plant samples that laboratories routinely receive.
Agreement beyond one instrument
The Cannabis Laboratory Quality Assurance Program, CannaQAP, adds comparison between laboratories. Its second exercise covered cannabinoids alongside moisture and toxic elements, enabling participants to examine how their results relate to those of other laboratories. Reference materials and comparison exercises serve different roles: one provides a stable benchmark, while the other exposes variation across real laboratory practices. Together with methods that distinguish interfering compounds, they make concentration data more comparable. That comparability is essential when research teams, regulators and laboratories exchange results produced in different places.
Sources & further reading
General information, not individual legal or medical advice.