INVESTIGATION OF THE VAPORIZATION AND ATOMIZATION OF BORON IN A GRAPHITE-FURNACE USING DIGITAL IMAGING TECHNIQUES

The distributions of atomic and molecular species of boron inside a gr aphite furnace were investigated with a charge-coupled device (CCD) ca mera, Extensive spatial nonuniformity of the distributions at high tem peratures was observed for both species, Digital imaging by the CCD ca mera showed that molecular boron species are preferentially formed at the top of the graphite tube at 1800-2000 degrees C and their concentr ations increase toward the center of the tube, The lowest concentratio ns of molecular boron species occur at the furnace wails and especiall y at the bottom of the graphite furnace, The highest concentrations of boron atoms occur along the graphite tube walls, at the bottom, The a bsence of significant concentrations of molecular species desorbing fr om the initial site of analyte deposition suggests: that the analyte b oron species, which do not absorb light at 254 nm, are vaporized, Sinc e the highest concentrations of the molecular boron species were detec ted away from the graphite tube wall, desorption of molecular boron sp ecies is not likely, A gas-phase thermal dissociation of boron oxide s pecies, resulting in the formation of BO (g), is suggested at temperat ures below the atomization temperature, Pre-atomization loss of boron as molecular boron species is clearly evident from the CCD images, The high appearance temperature (2300 degrees C) and high concentrations of atomic boron at the graphite tube wail suggest that much of the ato mic boron signal is probably the result of desorption of boron atoms f rom the decomposition of boron carbide (solid).