Breath-Pad Recovery Was Higher Than Overall THC Extraction Efficiency

Recovering THC from the collection pad was only one stage of analysis. The method’s favorable pad recovery did not mean that the complete preparation recovered the same fraction.

The validation separated stages

At the low quality-control level, direct THC recovery from fortified pads was approximately 85.5%, while overall extraction efficiency was approximately 33.8%. The researchers separately examined evaporation loss and solid-phase extraction recovery. Those measurements help locate procedural losses rather than treating preparation as a single invisible step.

The percentages have different denominators

Pad recovery compared selected preparation stages. Overall efficiency included additional processing. Neither is automatically the fraction of all THC in a participant’s exhaled air captured by the device, because fortifying a pad is different from challenging collection from an airborne sample. A recovery experiment also does not independently determine concentration bias after calibration and internal-standard correction.

What a device claim should state

Distinguish airborne collection efficiency, removal from the pad and subsequent extraction. The study validated a specific analytical process; its figures cannot be transferred wholesale to another device or used as a universal multiplier for a specimen. Breath detection remains evidence about recovered compounds under those conditions, rather than a direct measure of driving impairment.

Related analysis: actual breath-collection timing.

Research cited

Himes and colleagues (2013). Cannabinoids in Exhaled Breath following Controlled Administration of Smoked Cannabis. DOI: 10.1373/clinchem.2013.207407.