2.1. Apparatus
A microwave digestion unit and accessories (Multiwave,
Paar Physica), a centrifuge (Centaur 2, Sanyo), and an
ultrasonic bath (28H Ney Ultrasonik) were used for the
sample pre-treatment. A flame atomic absorption spectrometer
(AAnalyst 100, Perkin–Elmer Instrument) and a
graphite furnace atomic absorption spectrometer (4110
ZL, Perkin–Elmer Instrument) were used to determine
metal concentrations. The analytical conditions are summarized
in Table 1.