*3.2. Procedure*

A molybdenum metal target, not irradiated, was dissolved in hot concentrated H2O<sup>2</sup> 2 mL, and subsequently 3.5 mL of NaOH 6 M was added to convert MoO<sup>3</sup> into Na2MoO4.

In order to "mimic" the irradiated target conditions, a few microliters of generator eluted [99mTc]-sodium pertechnetate were added to the target solution. Subsequently, the sample containing the mixture of Mo and Tc (about 5 mL), together with the organic

phase MEK (5 mL), was pumped through the extraction-separation system, previously conditioned with the biphasic NaOH/MEK system (5 mL/phase).

The two phases converge, by means of a Teflon T-junction, in the capillary loop by forming a kind of train technically called the "slug-flow" regime (Figure 3b). The residence time in the loop is approximately 2.5 min and, at this stage, the transfer of [ 99mTc]TcO<sup>4</sup> −, from the aqueous to the organic phase occurs. Exiting from the loop, the two phases enter the ZAIPUT separator device, from which the technetium-rich organic and molybdenum-rich aqueous phases come out separated (ORG/AQ OUT 1 for the preconditioning, ORG/AQ OUT 2 for the sample).

**Figure 3.** (**a**) Operating principle with schematic representation of internal circulation within the two phases and (**b**) photo of a slug-flow regime in the loop in which the organic phase has been colored red by adding a dye.

Once drained of all the sample, a washing with the biphasic NaOH/MEK system (5 mL/phase) was performed to collect any residual sample in the system (ORG/AQ OUT 3). Between one experiment and another, the system was washed with water and MEK. All the samples collected at the output of the ZAIPUT device were then measured with an activity calibrator to detect the amount of 99mTc activity present in each sample, thus determining the extraction yield. The technetium was then extracted and purified from the 99mTc-rich organic phase with a silica and alumina column in series, preconditioned with 5 mL of MEK and 10 mL of deionized water, respectively. The technetium was then eluted from the alumina column with 3 mL of saline solution.
