Design and evaluation of a new programmed-scan spectrometer for multielement determinations by atomic emission

A new type of programmed-scan monochromator that employs a multiple entrance-slit dispersion system with stationary dispersion optics has been assembled and tested. The instrument uses an optical multiplexer, connected to the multiple entrance-slit spectrometer (MESS) by means of fiber-optic light guides, to illuminate up to eight entrance slits sequentially. A single high-sensitivity relatively inexpensive photomultiplier tube is used as the detector. A microcomputer interfaced with the detector is used to acquire data at a rate of approximately 4 sec per element and to control the optical multiplexer. Detection limits obtained from atomic emission measurements with an acetylene/air flame excitation source are reported for lithium, sodium, calcium, barium and strontium. The influence of signal averaging and sampling rate on system performance has been studied, and it was found that the delay time had essentially no influence on the measured signal-to-noise ratio.