Separation of transition metals on a poly-iminodiacetic acid grafted polymeric resin column with post-column reaction detection utilising a paired emitter–detector diode system

The selectivity, retention and separation of transition metals on a short (2 mm × 50 mm) column packed with a poly-iminodiacetic acid functionalised polymer 10 μm resin (Dionex ProPac IMAC-10®) are presented. This stationary phase, typically used for the separation of proteins, is composed of long chain poly-iminodiacetic acid groups grafted to a hydrophilic layer surrounding a 10 μm polymeric bead. Through the use of a combination of a multi-step pH and picolinic acid gradient, the separation of magnesium, iron, cobalt, cadmium, zinc, lead and copper was possible, followed by post-column reaction with 4-(2-pyridylazo) resorcinol (PAR) and absorbance detection at 510 nm using a novel and inexpensive optical detector, comprised of two light emitting diodes with one acting as a light source and the other as a detector. Column efficiency for selective transition metals was in excess of N = 10,000, with the baseline separation of seven metal cations in <3 min possible under optimised conditions. Detection limits of between 5 and 81 μg/L were possible based upon a 50 μL injection volume.