ICP-MS and XRF soil metal concentration screening comparison by quantitative analysis

Abstract

Urbanization increases human exposure to harmful and potentially deadly levels of toxic metals and their compounds from both natural background and anthropogenic fractions. Quantifying metal levels in soil and bedrock can result in highly variable concentrations. Detections for a suite of 18 metals (As, Ba, Cd, Cr, Co, Cu, Fe, Hg, Mn, Ni, Pb, Rb, Sb, Sn, Sr, Ti, Zn, and Zr) were conducted in my comparative analysis. My goals with this project are twofold: 1) quantify error and accuracy of the X-ray Fluorescence (XRF) against the Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) detection ability, accuracy and reliability, and 2) accurately determine which specific metals of the listed 18 are best screened for by XRF. To accomplish these goals I conducted analytical screening by XRF and compared results from ICP-MS for the 18 metals in a batch of 29 samples of young bay mud (San Antonio Formation). Soil samples were analyzed using the standard EPA method 6020 for bulk content by ICP-MS at a commercial laboratory, and XRF tests were performed in a lab on the SFSU campus. Results varied greatly with best fits to ICP-MS results: Zn, Pb, As, Hg, and Sn, and poorest fits: Cd, Zr, Ba, Co, Sr, and Cr. Highly significant statistical connection to concentration was found correlative (99.9% confidence) to the ability of the XRF to agree with ICP-MS soil metals screening analysis results.