This paper describes an approach to the determination of arsenic species bonding with proteins or low-molecular peptides by separation of leaf proteins and protein precursors into three fractions and analysis of arsenic species associated to these fractions. Plants irrigated with arsenite contained not only arsenite but also arsenate and dimethylarsinate. In plants treated with arsenate, the major component was arsenite in the water-soluble fraction containing soluble protein and non-protein (F II) and in the acid-soluble non-protein fraction (F IV). Concentrations of 43 mg kg⁻¹ (As(V)-treatment) and 18 mg kg⁻¹ (As(III)-treatment) could be analyzed in the water-insoluble structure protein fraction F I (56 ± 15% of the total mass).

Based on the concentration of arsenic species in all fractions, conclusions are drawn over the fixation of arsenic in the fraction of insoluble structure proteins, in the fraction of soluble cytosolic proteins as well as the fraction of amino acids.