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.
Smoking of drugs may result in the presence of residue in the mouth even after the passage of the detection period. Mouth swab testing is conducted by many employers as a random test on their staff to ensure that there is no drug abuse taking place.