Calibration standards for F-AAS and ICP-OES analyses were
prepared using Certiprep solutions (SPEX Certiprep, NJ, USA) in 2%
HNO3. Deuterium lamp background corrections were performed
for AAS. An internal standard containing 0.04 mg/L scandium and
0.2 mg/L yttrium was used for ICP-OES analyses.