What factors determine how much of a bioavailable chemical will be sequestered by an SPMD?
The amount of a chemical sampled by an SPMD is largely dependent on its sampling rate (liters of water or air extracted per day by an SPMD), Kow or analyte capacity, the water concentration, and exposure duration. Factors affecting sampling rate are complex, but nonpolar lipophilic organic compounds whose molecules have some conformational freedom (ability to rotate and flex) and are moderately sized (< 10 Å cross sectional diameter) are sampled at the highest rates. Assuming biofouling is minimal, a 1- g triolein SPMD will daily extract individual PAHs, PCBs, and organochlorine pesticides (OCs) from about 0.5 to 10 L of water. As the lipophilicity or Kow of a series of organic compounds rises, so does the capacity of the SPMD triolein to sequester them. For compounds with relatively large Kow's (i.e., > 100,000) longer exposure periods will typically result in greater analyte masses sequestered.
