The FI system was operated as follows: during the 60 s sample
loading period, with the valve in the ‘fill’ position, a sample (standard
or blank) at known pH buffered with acetic acid–ammonia
was pumped at 0.8 mL min−1 (via the peristaltic pump) through
the mini-column. The metals were adsorbed on the resin within the
mini-column and the sample matrix was allowed to pass through
to the detector. Then, with the valve in the ‘fill’ position, de-ionized
water was pumped at 0.8 mL min−1 through the mini-column for a
period of 1.5 min to wash the non-adsorbed metal ions and the remnants
of the matrix from the system. After preconcentration, the