## 4 Discussion
The system can accommodate three separate product vials with independent controlled valves that gives an advantage over the automated purification box developed by [PERSON] et al. that eluted purified \({}^{89}\)Zr in only one fraction vial [14]. As the maximum activity and EMA were found in fractions 1 and 2 (Figure 4 and Table 3), we usually prefer to combine only these two fractions for further studies. Using our system, greater EMA (1378 to 8892 vs. 5 to 353 Ci/mmol), more efficient separation with higher \({}^{89}\)Zr recovered activity (81 \(\pm\) 4.4% vs. 74 \(\pm\) 16%) and lower \({}^{89}\)Zr retention on the column (5 \(\pm\) 2.8% vs. 18 \(\pm\) 15%) were obtained, when compared to [PERSON]'s results [14]. Commonly, to achieve high EMA, the chemical must be metal trace with high purity \({}^{89}\)Y. To our knowledge, we reported in these studies the highest EMA values for \({}^{89}\)Zr that were produced by cyclotron by optimizing the \(E_{p}\), the amount/thickness and the current applied on the \({}^{89}\)Y-target. The highest EMA values were obtained while using packed \({}^{89}\)Y-foils. The EMA values achieved while using \({}^{89}\)Y-pressed targets well improves the value reported by [PERSON] et al. [5]. Pressed \({}^{89}\)Y targets are easy to prepare compared to electro-deposition preparation methods, which are also time consuming and less expensive compared to \({}^{89}\)Y-foil. They could represent an excellent alternative for routine production of \({}^{89}\)Zr. The preparation of both foil and pressed targets can be done in a few minutes. The cost for \({}^{89}\)Y-foil is \(\sim\)108 US$/irradiation using 2 foils (0.5-mm thickness and 13-mm diameter), while for \({}^{89}\)Y powder (0.5-mm thickness, 13-mm diameter, and 250 mg), the cost is \(\sim\)3 US$/irradiation, without considering the equipment costs. Admittedly, the use of pressed target comes at the cost of purchasing a press. This alternative strategy can rapidly be cost-effective if the press is used in the development of other solid targets and/or if the price of \({}^{89}\)Y-foil rises. One should note that \({}^{89}\)Y-powder 40-mesh (99.6% purity) that was used in this work contains more impurities than \({}^{89}\)Y-foil (99.9% purity). Particularly, 2000 ppm of Fe\({}^{+3}\) in \({}^{89}\)Y powder is responsible for the presence of the low amount of long half-life radiometal impurities (\({}^{56,57,58}\)Co) observed six months post irradiation. However, the metal impurity contents were almost similar for purified \({}^{89}\)Zr-oxalate solutions obtained from \({}^{89}\)Y-foil and pressed targets and it did not affect the labelling of \({}^{89}\)Zr with deferoxamine chelator (Table 4). Using our irradiation parameters and 11.3 MeV \(E_{p}\) for production of \({}^{89}\)Zr, no radionuclide impurities, such as \({}^{88}\)Zr and \({}^{88}\)Y were observed in purified fractions. However, when we increased the \(E_{p}\) to 13.3 MeV, trace of \({}^{88}\)Zr and \({}^{88}\)Y were observed on \(\gamma\)-ray spectrum measured after six months in the residual \({}^{89}\)Zr product solution after decay. The presence of \({}^{88}\)Y in the product solution after \({}^{89}\)Zr decay is not associated with the poor separation efficiency of the hydroxamate column, but is related to the decay chain of \({}^{88}\)Zr to \({}^{88}\)Y. \(E_{p}\) increases the production yield as well as the EMA, but it also increases production of long half-life impurities. This contamination will not affect image quality nor increase significantly the radiation exposure of the patient, but it must be considered when managing radioactive waste.