Performance optimization of a commercially available iminodiacetate resin for the determination of Mn, Ni, Cu, Cd and Pb by on-line preconcentration inductively coupled plasma-mass spectrometry

The on-line preconcentration performance characteristics of a commercially available iminodiacetate resin (Toyopearl AF-Chelate 650M) were investigate d. The method was optimized for several parameters, including buffer pH, ri nsing of matrix salts from the resin, elution acid type and strength, and t he nebulizer gas flow rate. An ammonium chloride buffer with a pH of 8.80 w as mixed with the sample on-line prior to loading. This pH was found to be optimal for Mn, Cu, Cd and Pb, whereas a pH of greater than or equal to9.2 was optimal for Ni analysis. Column rinse experiments showed that both buff er and water reduce Na concentrations to <100<mu>M in the rinse solution wi thin 3 min. It was also determined that using 1M HNO3 acid for column eluti on yielded higher intensities for Mn, Ni, Cu and Pb, while 1 M HCl yielded higher count rates for Cd. The change from the optimization solution, with a 0.2% HNO3 acid concentration, to the 10% elution acid required a reductio n in the nebulizer gas flow rate of 0.05 l min(-1) in order to obtain reduc ed blank intensity ratios. Calibrations performed using standard solutions (1 ml) with concentrations ranging from 0 to 10pg ml(-1) (ppt) resulted in regression coefficients of 0.990-0.998. Method detection limits of 1.1, 0.0 8, 0.47, 0.06 and 0.16 pg ml(-1) for Mn, Ni, Cu, Cd and Pb, respectively, w ere obtained. Accuracy was demonstrated by results from runs of the certifi ed standard reference materials (SRMs), CASS-4, a newly available coastal s eawater reference standard and NASS-4, an open ocean seawater reference mat erial. (C) 2000 Elsevier Science B.V. All rights reserved.