An automated apparatus for conducting a broad range of organic synthesis reactions includes a first column carring a polymeric support, a second column carrying a second polymer support, and conduits connecting the two columns and permitting the circulation of fluids therebetween. In operation each polymeric support carries a different reactive species and a liquid medium containing a specifically selected intermediate reactant, in a solvent, is circulated between the columns in order to remove the reactive species from the first support by reaction with the intermediate, and to permit the reactive species thus removed to react with the reactive second support, at the same time regenerating the original intermediate reactant. Sensors are placed at the entrance and exit of the second column carrying the second polymeric support. The sensors are capable of sensing the relative presence of the intermediate reactant. When the same content of intermediate reactant is sensed at both the entrance and exit of the second column, the computer causes the circulation to be automatically stopped as this indicates complete loading of the second column.