Evaluation of controlled-pore glass immobilized iminodiacetate as a reagent for automated on-line matrix separation for inductively coupled plasma mass spectrometry

A new iminodiacetate chelating reagent, immobilized onto a controlled-pore glass support, was evaluated as a substrate for on-line matrix separation for ICP-MS. An automated FI manifold was constructed, incorporating a glass mini-column of the iminodiacetate reagent. One compromise set of optimum conditions was obtained for a range of analytes, using the variables of matrix separation flow rate, buffer pH and concentration and eluent acid concentration. With a sample volume of 3 ml and an elution volume of 0.3 ml, a preconcentration factor of 10 was obtained in addition to matrix separation. The range of elements found to be retained by the column included transition metal cations, uranium and lead. These could be quantitatively eluted using nitric acid (0.5 mol dm–3). Calibrations prepared from both pure water and artificial sea-water matrices were found to be comparable in terms of sensitivity, illustrating that the presence of a saline matrix did not affect the separation process. Both calibration sets showed good linearity with least squares regression coefficients between 0.996 and 0.999 for the analytes measured. The method gave acceptable reproducibility with precisions (sr) at the 5 ng ml–1 level of <5%, for 5 replicates. Recoveries between 62 and 113% were obtained for all the elements analysed except Mn, which gave a very low recovery (<35%), under the compromise conditions used. The chelating material was found to have a capacity of approximately 0.1 mmol g–1 for a range of elements. The procedure was validated by accurate analysis of the National Research Council of Canada, CRMs SLEW-1 (Estuarine Water) and CASS-2 (Coastal Sea-Water).