AF4/ICP-ToF-MS for the investigation of species-specific adsorption of organometallic contaminants on natural colloidal particles

Organotin (OT) compounds are essential in various industrial applications, but they pose significant risks to both the environment and human health. The toxicity and transport dynamics of OTs depend on their specific chemical forms— i.e., the type and number of organic substituents—resulting in distinct toxicity profiles and varying affinities for environmental colloids. These colloids-species interactions collectively influence the mobility, bioavailability, and health impacts of OTs. To date, however, most studies addressed speciation and colloidal characterization separately; thus, the data on the combined determinations of the organometallic species in association with their carrier colloidal fractions remain largely elusive. Here, we present a comprehensive account of method development, application, and validation to quantitatively characterize the adsorption dynamics of 10 different OT species on natural colloidal particles (<500 nm). Our approach utilizes asymmetrical flow field-flow fractionation (AF4) coupled with inductively coupled plasma time-of-flight mass spectrometry (ICP-ToF-MS), achieving detection limits for Sn-equivalent concentrations as low as 6.0 ng/L. The method effectively separates free OT species from those bound to colloids, facilitates the fractionation of particles ranging from a few nm up to 500 nm, and enables the determination of fraction-specific OT interactions. This unique dataset offers comparative insights into the interactions of 10 OT species, representing a significant advancement in understanding species-colloid interactions. Our findings have important implications for assessing the distribution and mobility patterns of toxic organometallic species in surface waters, groundwater, sediments, and soils. The approach can be applied to an array of organometallics species (e.g., organolead, organomercury), generating essential experimental data that are critical for informed risk assessments and the improvement of regulatory frameworks.