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A sample changer designed to process automatically up to 48 2-cc samples is described. Mechanical drive mechanisms, digital electronics logic, and operational flow diagrams are presented. The changer is an integral part of a system consisting of an x-ray exciting source, a turntable changer, a Si(Li) radiation detector, and a preprogrammed pulse-height analyzer. X-ray fluorescence analysis of a sample allows quantitation of selected trace elements after simple spectral integrations are performed by an on-line microprocessor. Selection of the changer's MIX mode will cause each solution sample to be mixed just prior to analysis, thus insuring that representative tracer concentrations are determined.

Stable tracers are safe, convenient and readily available, but their use entails the need for involved assay techniques. X-ray fluorescence combines the use of stable tracers with the convenience of radioactive quantitation techniques. An automated system has been developed for use in medicine. Its performance and applications are presented.