Chemicals and Solutions.All of the reagents used were of analytical
grade. Deionized double-distilled water was used throughout the
experimental study. The Amberlite XAD-2 resin (Aldrich, Milwaukee,
WI) with a particle size of 20-60 mesh, a pore diameter of 90 Å, and
a surface area of 330 m
2
g
-1
was used. Before use, the resin was washed
with methanol and 4 mol L-1
HCl to remove impurities. 2-Hydroxyacetophenone and thiosemicarbazide were obtained from Fluka. Nitric
acid (Glaxo) was used without additional purification.
The following pH solutions were used for the SPE procedure: 1
mol L-1
HCl for pH 1 and acetate buffer between pH 2 and pH 6,
borate buffer at pH 7, and ammonium buffer between pH 8 and pH
10. A multielement standard solution (100µgmL-1
) was prepared by
dilution of ICP standards (Merck, Germany) of Cu(II), Ni(II), and Cd-(II). Working standards were prepared by appropriate dilution of the
multielement standard with double-distilled water.