In this system, the sample solution, maintained at pH 9.0, was pumped at 6.6 ml min−1 directly to the minicolumn containing 35 mg of functionalized resin.
After elapsed a suitable preconcentration time (typically 2 min), the valve was switched, and the eluent solution (2 mol l−1 HCl) then percolated through minicolumn at 4.9 ml min−1, desorbing the analyte from the solid-phase owing to a high
decrease in pH, what reduced resin complexing capacity.
Besides, formation of chloro-complexes of copper helped elution process. Afterwards, the sample plug was driven
to the spectrometer, where absorbance measurements were continuously made at 324.8 nm.
Thus, transient signals were derived, and peak heights were used as quantitative parameter. After the elution step, which takes about 22 s, the minicolumn is ready for a new preconcentration cycle.