Reagents and standards
All chemicals were of analytical grade unless otherwise
stated. Sub-boiled HCl and HNO3 were prepared in our laboratory
by sub-boiling distillation in quartz stills. Ultra-pure water
with >18M_cm resistivity, obtained using a Milli-Q high purity
water system, located in class 200 area, was used through out
thiswork. All containers were soaked in 20%HNO3 and cleaned
thoroughly with high purity water prior to use.
Tin(II) chloride (SnCl2) (5%, w/v) used as reducing agentwas
prepared by dissolving the appropriate amount of SnCl2•2H2O
(Merck, India) in HCl and diluting with water. Sodiumborohydride
(NaBH4) (Merck, Darmstadt, Germany) (0.5%, w/v)
was prepared fresh daily by dissolving the solid in 0.1% (w/v)
NaOH solution. A 10% (v/v) HCl was used as carrier. Thiourea
(NH2CSNH2) (Merck, Darmstadt, Germany) which has widely
been used for the preparation of resins for binding of mercury
as well as an eluent for stripping of mercury [45], was used in
the elution studies.