A novel method to determine trimethylantimony concentrations in plant tissue

Abstract

Environmental contextAntimony enters the soil mostly through mining and shooting activities and can thereafter be taken up by plants. In the soil, antimony may undergo several transformations such as biomethylation, leading to the formation of trimethylantimony. Here, we measured for the first time the uptake and translocation of trimethylantimony in a plant using a new extraction and analysis method. AbstractAntimony (Sb) is a relevant pollutant that can be found in elevated concentrations in soils near Sb mines and at shooting ranges. In soils, Sb occurs as trivalent Sb, SbIII, pentavalent Sb, SbV, or trimethylantimony, TMSb ((CH3)3SbO), the latter being the result of microbial biomethylation. It is important to understand the transfer of Sb species from soil to plants to assess the role of Sb in the food chain. However, this research has historically been hampered by the lack of suitable extraction and analytical methods. In this study, we validated an efficient and reliable extraction technique using oxalic acid and ascorbic acid (72.6±1.3% of Sb extracted) as well as a high-pressure liquid chromatography–inductively coupled plasma mass spectrometry (HPLC-ICP-MS) speciation analysis method to assess the uptake of TMSb in ryegrass (Lolium perenne L.), a common pasture plant, in a hydroponics experiment. Our results show that TMSb and SbIII are not converted to other species during extraction and that TMSb is taken up by ryegrass roots and translocated to the shoots. Our study also points at specific methylation–demethylation mechanisms occurring in the plant. Moreover, an unknown Sb species was found in the shoots of TMSb-treated plants, highlighting the need for further research. These new extraction and speciation methods will enable researchers to study the soil–plant transfer of organo-Sb compounds in a reliable and consistent manner.