Samples were digested using a digester block and a reflux
system that included a cold finger
Aliquots
of each sample were placed into individual glass tubes
4 mL of concentrated nitric acid
and 2.0 mL of 30% (v/v)
hydrogen peroxide
were added to each tube. The samples
were then digested for 60 min at 110 C.
Subsequently, the digested
samples were transferred to a 25-mL volumetric flask
and
ultrapure water was then used to fill the volumetric flask to
25 mL. During the determination of cadmium the sample volume
injected in the graphite furnace was also 20.0 lL.