Reagents and standard solutions
Analytical reagent grade chemicals were employed
for the preparation of all solutions. De-ionized
water prepared from a Milli Q water purification
system (Millipore, Bedford, MA, USA) was used
throughout this work. Stock standard solutions
(1000 mg/l) of Cd(II) and Pb(II) were obtained
from the National Institute of standard and Technology
(NIST) and diluted for obtaining reference
and working solutions. Certified reference material
(DORM-2) was obtained from the National
Research Council Canada (NRC) for method verification.
Mg(NO3)2 and NH4H2PO4 were used in the
preparation of chemical modifiers.