The Plasma Assay’s Sensitivity Depended on Its Validated Specimen Volume
The published plasma assay used a one-milliliter specimen in its preparation procedure. Its concentration sensitivity cannot automatically be assigned to a much smaller-volume version of the method.
Volume was part of the workflow
The protocol precipitated proteins from 1 mL plasma with 2 mL acetonitrile before extraction, evaporation and derivatization. Its reported lower quantification limits included 0.1 ng/mL for THC and 11-hydroxy-THC. Those values describe the complete tested procedure, not an instrument specification independent of specimen preparation.
Concentration and available amount differ
At the same concentration, a smaller specimen contains less analyte. Changing volume can also change recovery, matrix contribution and final extract composition. A miniaturized procedure may perform well, but that is an empirical validation question. The paper did not demonstrate that an arbitrary smaller aliquot retains all of its reported performance.
What a laboratory comparison requires
Review the volume actually processed, extraction and concentration steps, injection conditions and current lower-limit data. A different laboratory may have validated a lower-volume method; this publication neither certifies nor disproves it. The study concerns analytical quantification in plasma for research, with stated limits on forensic transfer. Sensitivity at a defined volume is not evidence of an individual’s dose or degree of impairment.
Related analysis: the plasma method’s intended research use.
Research cited
Andrenyak and colleagues (2017). Determination of THC, 11-hydroxy-THC, THC-COOH and Cannabidiol in Human Plasma using Gas Chromatography–Tandem Mass Spectrometry. DOI: 10.1093/jat/bkw136.
