Exploring Matrix Effects on the Determination of Iron in Soil Using X-ray Fluorescence

Abstract

X-ray fluorescence (XRF) spectroscopy is a powerful tool for the multielement analysis of a wide variety of samples. Due to the perceived cost and complexity of the experiment, it has not been widely adopted in the undergraduate laboratory curriculum. Presently, the cost to purchase an XRF instrument is on the order of flame atomic absorption instrumentation, and the use of an XRF instrument is quick to master. Qualitative work is very straightforward, but because of matrix effects, quantitative work provides some interesting challenges and educational opportunities. The quantitative analysis of iron in soil provides an ideal example of the degree to which matrix effects in solid samples attenuate analytical signals and allows the comparison of different calibration methods. The prevalence of finding iron in local soil makes this experiment widely applicable and relatively safe, given the benign nature of the analyte. Student groups perform different calibration methods and, after the lab rotation is complete, compare their results in order to unravel what calibration method best compensates for the matrix effects observed in a soil sample.