Continuous Online Leaching System Coupled with Inductively Coupled Plasma Mass Spectrometry for Assessment of Cr, As, Cd, Sb, and Pb in Soils

Incidental ingestion of soil containing Cr, As, Cd, Sb, and Pb has been attracting global attention as it can significantly impact human health. Many bioaccessibility methods have been developed to simulate the amount of contaminants extracted by gastrointestinal fluids following incidental ingestion. Although the continuous online leaching method (COLM) offers various advantages over conventional batch bioaccessibility methods, such as reduced analysis time, elemental source apportionment, and isotopic analysis, it has not yet been applied to soil and directly compared to validated, published methods. This study uses the COLM with simulated gastrointestinal fluids from the United States Environmental Protection Agency (US EPA), United States Pharmacopeia (USP), and unified bioaccessibility method (UBM) to measure the bioaccessibility of Cr, As, Cd, Sb, and Pb in NIST 2710, NIST 2710a, NIST 2711a, and BGS 102. When the US EPA gastrointestinal fluid was used, no significant difference was observed between the COLM bioaccessible + residual, aqua regia extraction, or certificate concentrations for all the elements and soils studied. Furthermore, COLM bioaccessibility was within the acceptable range of control limits and bioavailability (animal) studies for most reference materials. In addition, no statistically significant difference was observed between either the US EPA batch method or the stomach phase of the UBM batch method and the stomach stage of the COLM, indicating that the COLM could be incorporated into current bioaccessibility analyses to improve soil contamination characterization in the future.