LOW-TEMPERATURE MIGRATION OF LEAD, THALLIUM, AND SELENIUM ONTO A PALLADIUM MODIFIER DURING THE ANALYSIS OF SOLUTIONS AND SLURRIES BY ELECTROTHERMAL ATOMIC-ABSORPTION SPECTROMETRY

A palladium/magnesium modifier, when premixed with solutions or slurri es, stabilizes many analytes to higher pyrolysis and atomization tempe ratures. Similar behavior was seen when analyte and modifier were phys ically separated by pipetting them onto opposite sides of a L'vov plat form. During the pyrolysis stage of the furnace heating cycle, lead, t hallium, and selenium migrated from the platform surface and interacte d with the modifier on the opposite side. This behavior explains the c onsistent stabilization by palladium of analytes in slurry samples. Un der conventional operating conditions the modifier is premixed with th e slurry, and on drying in the furnace, the analyte and modifier may n ot make close contact. However, this is unimportant since the analyte will migrate to the palladium on heating. Then the rate-limiting step leading to atomization is the release of analyte from palladium, and i t is the same for solutions and slurries. Therefore, aqueous standards can be used for slurry analysis.