Imaging of I, Re and Tc plant uptake on the single-cell scale using SIMS and rL-SNMS

In radioecological studies, there is a significant need for understanding the plant uptake of radionuclides on a cellular level. The present work applies mass spectrometry to image the radionuclide distribution within the cellular structures of plants at varying concentrations. In a first step, plants of Daucus carota and Pisum sativum labelled with iodine and rhenium were examined, at concentrations in the range of 10 mM. Cross sections of several plant parts were imaged by secondary ion mass spectrometry (SIMS) after cryogenation in order to preserve cell structure. In a second step, the distribution of ⁹⁹Tc in the two plant species was determined. For radiological reasons, a concentration three orders of magnitude lower was used, rendering measurements with SIMS impossible. Therefore, resonant laser secondary neutral mass spectrometry (rL-SNMS) was used for the first time to image ⁹⁹Tc with suppression of molecular isobaric interferences. The measurement of only about 10¹⁰ atoms of ⁹⁹Tc atoms is demonstrated and the distribution of ⁹⁹Tc within a single epidermal cell is imaged.