Complexing porous polymer monoliths for online solid-phase extraction of metals in sequential injection analysis with electrochemical detection.

A monolithic column affording complexing groups was synthesized for automated solid-phase extraction of potentially toxic metal ions in a low-pressure sequential injection analyzer. Poly(glycidyl methacrylate-co-ethylene dimethacrylate) monoliths were synthesized by free-radical polymerization in the coffins of fused silica-lined stainless-steel tubes (2.10 mm i.d. × 5-6 cm length). High permeability (4.33 × 10-13 m2) was achieved for monoliths polymerized for 24 h at 60 °C from a mixture of 30 wt% glycidyl methacrylate, 10 wt% ethylene glycol dimethacrylate, 35 wt% n-propanol, 20 wt% 1,4 butanediol and 5 wt% water. Azobisisobutyronitrile (1 wt% with respect to the monomers) initiated the free-radical polymerization. These generic columns were modified with iminodiacetate to create complexing functionalities on the polymer surface, being further used for online solid-phase extraction of Cu2+, Pb2+ and Cd2+ from natural, tap and drinking waters prior to their determination by stripping chronopotentiometry. The high permeability of the column allowed the loading, washing, eluting and reconditioning steps to be made at flow rate of 10 µL s-1. The limits of detection and quantification achieved by processing 1500 µL of sample were 0.51 and 1.7 µg L-1 for Cu2+, 1.4 and 4.7 µg L-1 for Pb2+, and 1.2 and 3.8 µg L-1 for Cd2+, respectively. Recoveries were between 75.5% and 117%, obtained by quantification via external calibration curves, thus eliminating the need for the laborious standard addition strategies.