Flow injection manifold for matrix removal in inductively coupled plasma mass spectrometry by solid phase extraction: determination of Al, Be, Li and Mg in a uranium matrix

Abstract

A flow injection manifold, incorporating two pumps and an 8-port rotary valve, was developed for the automation of a procedure for the removal of the matrix suppression of uranium on light elements. The procedure was based on the selective retention of the uranium on a column of TRU.Spec ^® resin (a support material impregnated with a liquid ion-exchanger). The light elements were not retained. The uranium was removed by 0.2 mol l ^–1 ammonium oxalate solution and the column reconditioned by the passage of 25% (v/v) nitric acid. The interference of uranium, 5000 mg l ^–1 , was removed, allowing the determination of aluminium, beryllium, lithium and magnesium at concentrations down to a few µg l ^–1 in 100 µl of sample. The sample acidity was 20% and the carrier stream was 5% with respect to nitric acid. Although higher acid concentrations could have improved the retention of uranium, the acid concentration was not increased to avoid degradation of the nickel sampling and skimmer cones. A complete analysis cycle took 4 min, including the regeneration of the column.