New theory of time integrative passive samplers.

Current theoretical, two compartment description of integrative passive sampling is renewed to establish a three-compartment model. The developed theoretical description includes external chemical conditions near the receiving phase, conditions inside the receiving phase and the chemically bonded compartments. New variable p, which controls the chemical bonding process into the sampler receiving phase is introduced. This new theoretical model enables derivation of equations for accumulation of masses in situations where convective mass transfer coefficient (h) and chemically bonding activity (p) are defined as a piece-wise constant functions of time. Previous two compartment model, which connects time average external concentration and accumulated mass is derived directly to the case where h and p are constants during the whole observation period. For other situations more complex equation is derived. Applicability of new equations are tested in laboratory experiments with fluctuating external chemical concentration.