Sample dissolution for the determination of total concentrations
was performed with a Milestone MLS-1200 Mega (Milestone,
Sorisole, Italy) microwave laboratory unit.
Metal determinations were carried out with a Varian Liberty
100 model (Varian Australia, Mullgrave, Australia) inductively coupled
plasma-atomic emission spectrometer (ICP-AES). The calibrations
were always performed with standard solutions prepared in
aliquots of sample blanks.
High purity water (HPW) produced with a Millipore Milli-Q system
was used throughout. All the reagents used were of analytical
grade. Standard metal solutions were prepared from concentrated
stock solutions (Merck Titrisol