All reagents were analytical grade. Nitric acid was purified by
sub-boiling distillation in a duoPUR acid purification system (Milestone
Inc., USA) prior to use. Water was ultrapure grade
(18.2 mX cm1
, Millipore Corp., USA). Analytical calibration standards
diluted in 2% (v/v) nitric acid were prepared daily from stock
standard solutions (Choice Analytical Pty Ltd.). Rhodium and
yttrium were used as internal standards for ICP-MS and ICP–OES.