Abstract
Diffusive monitoring of fluctuating concentrations is analyzed for the situation in which the concentrations of each component of a mixture to be sampled do not necessarily remain close to zero at the sorbent surfaces. Considering first samplers with a single sorbent surface, an estimate of time weighted averages (TWA) of the concentration in terms of measured mass is given which is unbiased in the limit of small concentrations. Bounds on the fluctuation-related error in this estimate are derived which may be calculated from the collected masses of any given sample. The error limits relate to both linear as well as leading non-linear regions of the empirical sorbent isotherm. The error limits imply potentially excessive error in the estimation of concentrations over averaging times as long as 8 hours. Reduction of this error and detection of breakthrough through the use of multiple sorbent surfaces is discussed.