Comparison of AAS, ICP-MS, and pXRF Performance for Copper Analysis in Agricultural Soils

Abstract

Accumulated copper (Cu) in agricultural soils is non-biodegradable and persists in the environment, which imposes the need for its regular monitoring by selective, rapid, simple, and low-cost analytical techniques. The performance of portable X-ray fluorescence spectrometers (pXRF) has significantly improved in the last ten years, and they are increasingly applied for environmental, agronomic, and soil science purposes. This study aims to compare the total Cu content determined in agricultural soil samples using three analytical methods (inductively coupled plasma mass spectrometry, (ICP-MS), atomic absorption spectrophotometry (AAS), and pXRF). The research was based on analyses of thirty-five soil samples collected from two vineyards, arable land, and a meadow located in North-West Croatia. In air-dried, milled, and homogenized soil samples, Cu content was detected using a hand-held XRF analyzer under laboratory conditions, while ICP-MS and AAS analysis were performed after open digestion by aqua-regia. Determined Cu content varied in very similar ranges from 51.2 mg/kg to 444.3 mg/kg with an average of 138.9 mg/kg for AAS; from 48.6 mg/ kg to 446.4 mg/kg and an average of 139.7 mg/kg for ICP-MS and from 54.0 mg/kg to 435.3 mg/kg with an average of 141.3 mg/kg for pXRF. A high positive correlation between Cu content determined by pXRF and ICP-MS (R2 = 0.996), as well as between pXRF and AAS (R2 = 0.997), along with the results of Bland-Altman statistical analysis indicate that pXRF can be applied as a reliable tool for analyses of Cu-contaminated agricultural soil.