Abstract: In a microprocessor-controlled evaporation/concentration system, a plurality of sample solutions are automatically successively delivered to an evaporation chamber. Each sample solution is evaporated in successively delivered slug components. The underside of the bottom wall is maintained at a microprocessor-determined constant evaporation temperature by an electrical resistance heater and proportional temperature controller. Pressure in the chamber is maintained substantially on the vapor pressure versus temperature curve of the sample solution, thereby assuring a known evaporation rate. Valving controlled by the microprocessor permits automatic addition of diluent to the chamber. The prepared sample is then automatically transferred to one of multiple storage vials which are brought into successive registration with a syringe needle assembly by means of a rotatable vial storage tray.