The ionic composition of interstitial and intravascular fluids is the same. Proteins, however, are kept with the vascular compartment, at least to a degree, by the vascular wall, which is a semi-permeable membrane. The concentration of proteins is much higher in the plasma sector than in the interstitial sector.
Detection of marijuana using swab drug test can vary from person to person taking into account the different conditions like general health, different fluid intake, metabolism, etc.
Cannabix is working to develop a drug-testing device that will detect Tetrahydrocannabinol (THC-the psychoactive component of marijuana that causes intoxication) using breath samples. The device would be used to provide detection of THC at the roadside to identify drivers intoxicated by the use of marijuana.