Automatic sample feeder for flameless atomic absorption spectrometer

Abstract

Apparatus for injecting a selected one of a plurality of samples into a graphite tube atomizer of a flameless atomic absorption spectrometer. A sample dilutant or blank solution, a standard solution for calibrating the spectrometer, and each of a plurality of unknown sample solutions are continuously fed into separate overflow vessels mounted in a turntable driven by a servomotor and monitored by a suitable analog-to-digital encoder. Each of the vessels overflow into a common drain channel and the vessels are positioned by a control system so that a small sample from selected vessels that may contain an unknown sample, dilutant, or calibrating standard, is drawn by a pump into an intake tube. A servomechanism then repositions the tube into the graphite tube atomizer and the pump reverses to inject the solution into the atomizer. The control system is programmed to operate in proper sequence: the spectrometer, the intake tube servomotor, and also to position the turntable and operate the intake tube pump as well as a rinse pump that flushes the entire input tube. The dilutant and standard solutions are supplied from large containers positioned on weight monitors that produce alarms when the solutions are nearly exhausted. This alarm system, together with automatic sample feeding and the use of the overflow vessels on the turntable, eliminates the need for continual manual monitoring by a technician.