Implementation of an iterative approach to optimize synchrotron X-ray fluorescence quantification of light elements in single cell

A new approach for elemental quantification and error estimation in single cells, named Single Cell Elemental Quantification Iterative Approach (SCEQIA), has been performed merging two analytical approaches conceptually different. The first one is a multimodal approach designed to identify and quantify the concentration of light elements in biological samples and to calculate errors following error propagation law. The second one is an iterative algorithm conceived to quantify heavy elements in terms of mass fraction in mineral samples and to evaluate errors using an iterative Monte Carlo-based procedure. The fluorescence data and scanning transmission data, provided by synchrotron X-ray microscopic techniques, together with the volumetric data from Atomic Force Microscopy (AFM) of two colon carcinoma cells have been analyzed following SCEQIA approach. The mass fraction and the molar concentration of the elements C, N, O, Na, and Mg have been mapped. The obtained results have been compared with those previously provided with the original multimodal approach above mentioned. The outputs of the two approaches are comparable in terms of elemental quantification (mass fraction and concentration) for both the analyzed samples. On the contrary, the two approaches differ in error estimation: the newly developed SCEQIA approach results less influenced by the uncertainties of AFM measurements.