A purge and trap concentrator has a sample processing system that includes a network of fluid passageways and fluid control devices. A flow controller couples to a purge gas inlet provides an electrically adjustable purge gas flow rate as a function of an electrical input. A digital controller provides the system cycle and provides the electrical input. The electrical input varies as a function of the system cycle to increase the rate of flow of purge gas during a bake step relative to the rate of flow of purge gas during a purge step in the system cycle.