Abstract

Matrix effects were evaluated on the determination of Dy, Eu and Yb used as sheep faecal markers by inductively coupled plasma optical emission spectrometry (ICP-OES) with axially- and radially-viewed configurations. The samples were prepared with microwave-assisted acid digestion using an oven with closed vessels. The analytical performances of the two ICP-OES instruments were compared using Mg II/Mg I intensity ratios at different operating conditions. The values obtained using the axially-viewed ICP were 6.5 (1.3 kW and 0.7 l min⁻¹) and 4.8 (1.0 kW and 0.9 l min⁻¹). These values were higher than those determined using radially-viewed ICP-OES, 5.2 and 2.5, respectively. Under all operating conditions and for all elements measured, the detection limits obtained with the axially-viewed configuration were at least three-fold better, but were more critically affected by incremental background emission increases at a higher plasma power and lower nebulization gas flow rate. The accuracy of the Dy, Eu and Yb determinations in acid-digested faecal samples by axially- and radially-viewed ICP-OES was verified using the INAA technique, and a paired t-test showed that all results were in agreement at a 95% confidence level.