a sample introduction system includes a drop chamber which can be sealed and outgassed and which includes a movable jaw selectively holding the sample in position above a conduit communicating with an open crucible for receiving a sample once the jaw has been moved to an open position releasing the sample . the jaw is actuated by a magnetic field which moves the jaw in an entirely enclosed system , thereby preventing the introduction of atmospheric contaminants during the operation of the sample dropping jaw from a closed , sample holding position to an open sample releasing position . by providing a magnetic actuator , such as a solenoid , for operation of the jaw , the sample chamber remains sealed during the sample dropping operation preventing contaminants from interfering with the analytical results .