2.5. On-line solid phase extraction procedure
The flowinjection systemand the experimental set-up are shown in
Fig. 1. Before loading (and after each cycle of Sb(III) retention/elution)
the system was washed with 1 mL of a 15% (v/v) HCl solution and
then with 2.5 mL of DDW. An aliquot of sample was then loaded on
the microcolumn delivered by Pump 1 at flow rate of 3.0 mL min−1
with FIAS-valve in load position. After that, FIAS-valve was switched
to the elution position and Sb(III) retained was eluted with a 15% (v/
v) HCl solution at a flow rate of 6.6 mL min−1. The acidified eluate
was on-line merged with the reductant (delivered by Pump 2 at flow
rate of 3.5 mL min−1) into the reaction loop and subsequently carried
to the gas–liquid separator. Reaction loop volume was kept as small as
practicable to avoid broadening of the signal peak. The volatile stibine
generated was separated from the solution and swept by N2
(30 mL min−1) into the quartz cell and the determination was carried
out.