Minimization of interferences in inductively coupled plasma mass spectrometry using on-line preconcentration

Abstract

A semiautomated system is used to preconcentrate Ti, V, Mn, Fe, Co, Ni, Cu, Cd, and Pb, in order to remove high salt matrices. The preconcentration system accepts digests with acid concentrations equivalent to 0.8-1.4% HNO{sub 3}, neutralizes them, and loads them onto a macroporous iminodiacetate resin. The alkali and alkaline-earth metals, along with deleterious anions such as chloride, are washed off the resin before and analyte metals are eluted with nitric acid. A total of 13 isotopes of the analytes are measured. An examination of the apparent concentration efficiencies, as well as the behavior of two internal standard elements added to the eluate stream, indicates that the elution front matrix enhances the inductively coupled plasma mass spectrometry response of the analytes. Investigation of the nature of the blank signal suggests that the detection limits of several of the isotopes could benefit by much larger preconcentration factors, while those of vanadium, copper, cadmium, and lead are currently limited by reagent purity and laboratory contamination. The preconcentration system is evaluated on several simple synthetic matrices, as well as on synthetic seawater and three wastewaters. Digestion of samples containing natural organic chelators is required.