The theoretical flow system described is able to detect and determine iodide at concentrations in the range 0.01-10 μM in samples as small as 120 μl. This represents the best limit of detection (0.15 ng) thus far reported for a thermochemical methodology. It is shown that sample concentration can alter the relationships between peak height and flow rate, and between peak width and sample volume above certain limits. In chemical engineering, studies of chemical reactions in the presence of mass transport processes have generally been focused on the steady-state (time-independent) behavior. The present work is concerned with transient phenomena and time-dependent properties of the system, i.e., the reactors are used under pulsed conditions.