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.
About 14-21 days. Marijuana is a fat soliuble drug which means that it stays in your fat cells. ChaCha on! [ Source: http://www.chacha.com/question/how-long-do-mouth-swabs-test-for-weed ]. More Answers to  How long do mouth swabs test for weed .