ISOTOPE-SHIFT ZEEMAN EFFECT SPECTROMETER

Apparatus and method employing a beam containing specific Zeeman components for rapidly and accurately detecting the presence of trace amounts of a specific biologically dangerous metal element, such as Hg, that contaminates a host substance, such as food. In one embodiment for detecting Hg in fish, the apparatus comprises first means for heating a fish sample containing mercury to 950 DEG C to form a vapor, second means for transmitting a focused light beam through the vapor in the form of light spectra produced from a mercury isotope in a magnetic field parallel to the light spectra, said spectra containing 2537 A light having specific Zeeman components that are equally scattered and differentially absorbed by the Hg in the vapor, comprising a circularly polarized sigma monitoring component that is attenuated by absorption by the mercury in the vapor an amount corresponding to the amount of mercury in the sample and a circularly polarized unabsorbed sigma reference component, said beam then being transmitted through a circular polarization selector for alternately periodically transmitting the respective components passing through the vapor, and a filter for passing only the 2537 A from the transmitted light beam to means for detecting said remaining components after the beam is so transmitted, as a measure of the mercury in the sample. In practice, a rotating quarter (1/4 lambda ) plate and a linear polarizer having a 2537 A filter alternately periodically transmits the respective components to a single photomultiplier for providing a light-weight, portable detector.