Reagent delivery system for use in solid-phase analytical devices

A reagent delivery system for use in solid phase analytical devices is disclosed. Matrices containing a reagent dispersed in a water soluble polymer that controls the dissolution rate are positioned over a reaction matrix such that sample liquid dissolves the conjugate to perform a solid-phase immunoassay reaction. The matrices are then removed from the reaction matrix where a detectable signal is formed for the particular solid-phase immunoassay performed.