MINIMIZING CHLORIDE INTERFERENCES PRODUCED BY COMBINATION ACID DIGESTION USING PALLADIUM AND HYDROGEN AS A MATRIX MODIFIER IN GRAPHITE-FURNACE ATOMIC-ABSORPTION SPECTROMETRY

The use of Pd/Mg(NO3)2 and 5% H-2 as a modifier is evaluated as a method of reducing the chloride interferences produced by a mixed-acid digestion. The presence of 10-mu-L of 2% HCl produces suppressions which range from 15 to 90% for As, Sn, Pb, Cd, and Tl with the use of Pd/Mg(NO3)2 as the modifier. The use of Pd/Mg(NO3)2 along with 5% H-2 (during the dry and the char) reduces the suppression to less than 5% for Pb, Cd, and Tl. The use of Pd and 5% hydrogen as the matrix modifier for tin reduces the suppression caused by the HCl to less than 5%. In addition, if the 5% H-2 gas mixture is not adequately purged from the furnace prior to atomization, the selenium response is reduced by 18%.