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.
While often inaccurately referred to by employers and drug testers as an impairment test, urinalysis can not detect the presence of any illicit drugs â including marijuana â and can only identify the presence of non-psychoactive drug metabolites indicating that a substance has been previously consumed at an unspecified point in time.