Spectrofluorimetric flow-injection determination of cerium in carbon and low alloy steels

Cerium can be determined spectrofluorimetrically (λem 350 nm, λex 260 nm) based on the relatively intense native fluorescence of the cerium(III) aquo-ion. The main potential interference in the analysis of steel from iron(III), cerium(IV) and chromium(VI) are removed by use of a carrier solution containing 2.5% w/v hydroxylammonium chloride. The slight residual interference from iron(II) can be corrected by a matrix matching factor linearly related to the amount of iron present. The calibration graphs are linear over the range 0–7 μg ml−1 based on 250 μl injection volumes. The sampling rate was 30 h−1. The relative standard deviation was 2.0% (n=5) at 3 μg ml−1 cerium. The system has been applied to the determination of cerium in carbon or low alloy steels.