A Gilson Minipuls 3 (Villiersle Bel, France) peristaltic pump provided with flexible PVC tubes was used to propel the solutions.
A Rheodyne 5041 (Cotati, CA, USA), six-port rotary valve was used to select preconcentration or elution steps.
The system manifold was built of PTFE tubes with 0.5mm i.d. and connections made of PEEK.