Kinetic and Equilibrium Sampling

Equation 3.13 shows that the concentration in SPMDs gradually increases with time until equilibrium is attained. When kj 1, Cs attains its equilibrium value 

In this case, the exposure mode is called equilibrium sampling . When kj C 1 (short exposure times and/or highly hydrophobic compounds), the group between 

Because Cs increases linearly with time, this phase of an exposure is called kinetic sampling , or the linear uptake mode , and sampling is time-integrative. The amount (N) absorbed by SPMDs during kinetic sampling equals 

The aqueous concentration can therefore be calculated from the absorbed amounts by 

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