Evaluation of different quantification modes for a simple and reliable determination of Pb, Zn and Cd in soil suspensions by total reflection X-ray fluorescence spectrometry

In view of the large number of soil analyses in environmental studies dealing with metal contamination, the use of simple, fast, sustainable and cost-effective methodologies is desired. In this sense, the role of total reflection X-ray fluorescence spectrometry (TXRF) has to be highlighted due to the possibility of direct analysis of solid suspensions without the need for a digestion process. Internal standardization is successfully used as a quantification approach in multielement TXRF analysis of liquid samples, including soil digests. However, its application for the analysis of soil suspensions is not always possible. In the present manuscript we found that although acceptable results were obtained for TXRF quantification by internal standardization when considering soil certified reference materials (recoveries: 80-120%), a systematic underestimation of the concentration values was found when using the same approach for real soil sample analysis (recoveries