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.
Approximately 90 percent of drug tests are done as urine tests. Other tests using saliva, hair, sweat and blood samples can also analyze and detect traces of marijuana in your system. Hair testing provides a longer window of detection than urine and can detect drugs taken within the past 90 days.