Fe 2 sulfate

Analytical grade TBH (>99% purity) and heptahydrated Fe(II) sulfate were supplied by Sigma-Aldrich. Supporting electrolytes like sodium sulfate and lithium perchlorate were of analytical grade purchased from Fluka. High-purity Millipore Milli-Q water (resistivity > 18 MΩ cm) was used for the preparation of all solutions. Their initial pH was adjusted to 3.0 with concentrated sulfuric acid of analytical grade purchased from Merck. All the other chemicals were of HPLC or analytical grade supplied by Merck, Panreac and Sigma-Aldrich.

Human colon adenocarcinoma cell lines-HT-29 and HCA-7-were grown at the 2nd Institute of Pathology, Budapest, Hungary in 37 °C in a humidified atmosphere consisting of 5 % v/v CO 2 in an antibiotic-free medium supplemented with 10 % v/v fetal calf serum (FCS) supplied by Sigma-Aldrich (St. Louis, MO, USA). The HT-29 and HCA-7 cells were obtained from ECACC (European Collection of Cell Cultures, UK). For the growth of HT-29 and HCA-7 cells, RPMI-1640 (Roswell Park Memorial Institute) and DMEM (Dulbecco's Modified Eagle Medium) growth media were used, respectively.
The reagent grade Tf, Fe(III) citrate, ethylene diamine tetraacetic acid (EDTA), Fe(III) chloride, Fe(II) sulfate and Fe(III) sulfate hydrate standards were supplied by Sigma-Aldrich. For the TXRF-XANES experiments, on one hand, Fe(III) sulfate hydrate was used in the solid state of matter referred further in the manuscript as deliquescent Fe(III) sulfate. On the other hand, this deliquescent Fe(III) sulfate was dissolved either in deionized water or dimethyl sulfoxide (DMSO), referred further as Fe(III) sulfate (aq) and Fe(III) sulfate (DMSO), respectively. The concentration of the latter two Fe(III) sulfate stock solutions was 10 mg/L for Fe. From each stock solution, 1 µL containing 10 ng of Fe was pipetted directly onto the quartz reflectors and dried immediately.