Determination of cobalt in soil, steel, and graphite using excited-state laser fluorescence induced in a laser spark

An LIES/LEAFS (laser-induced breakdown spectroscopy/laser-excited atomic fluorescence spectrometry) combination with the use of simple open-air ultraviolet (UV) ablation has been investigated in terms of its analytical possibilities for the determination of cobalt in three solid sample matrices: graphite, soil, and steel. The fluorescence of cobalt was excited from a level which was already populated in the ablation plasma and was monitored at the Stokes-shifted wavelength. The optimal time delay between the ablating and exciting pulses was 16 mu s. Detection limits in the ppb to ppm range and linearity over about four orders of magnitude were obtained. Excellent correlation of the LIES/LEAFS with laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) and the certified value for Co in an SRM soil standard showed that both the precision and the accuracy of the LIES/LEAFS method were satisfactory.