2. Reagents
Analytical grade chemicals were employed in the processing of
all samples. Nitric acid (HNO3) was obtained from Sigma–Aldrich
(Buchs, Switzerland). Distilled de-ionised water was used in all
experiments. All plastic and glass wares were properly cleaned
by soaking with 2 M nitric acid and rinsed thoroughly with deionised
water before being used. The standard solutions of analytes
for calibration procedure and spiking, obtained from Sigma–
Aldrich, were prepared by diluting stock solutions of 1000 ppm
for each of the investigated elements.