Uncertainty Estimation for the Determination of Fe, Co and Ni in Natural Water Samples by SPE-ICP-OES

Abstract

This work describes measurement uncertainty estimation for determination of Fe, Co and Ni in natural water samples by solid-phase extraction and inductively coupled plasma optical emission spectrometry (SPE-ICP-OES). The procedure is based on the retention of analytes in the form of 8-hydroxyquinoline (8-HQ) complexes on a mini column of XAD-4 resin and subsequent elution with nitric acid. To estimate the uncertainty of analytical result obtained, we propose assessing trueness by employing spiked sample. Two types of bias are calculated in the assessment of trueness: (i) a proportional bias and (ii) a constant bias. We applied Nested design for calculating proportional bias and Youden method to calculate the constant bias. The results obtained for proportional bias are calculated from spiked samples. In this case, the concentration found is plotted against the concentration added and the slop of standard addition curve is an estimate of the method recovery. Estimated method of average recovery in Karaj river water is: (1.0198 ± 0.0075) for Fe, (1.0215 ± 0.0133) for Co and (1.004 ± 0.0085) for Ni.