## 3 Results and Discussion
\begin{table}
\begin{tabular}{c c c c} \hline
**Bombardment** & **Predicted Activity** & **Estimated Total** & **Effective Specific** \\
**Time** & **from Cyclotron** & **Activity** & **Activity** \\
**h (μA\(\cdot\)h)** & **mCi** & **mCi** & **mCi\(\cdot\)umol\({}^{-1}\)** \\
**h (μA\(\cdot\)h)** & **mCi** & **(\% of Predicted)** & **(\% of _TS4)** \\ \hline
4 (60) & 79 & 62 (78\%) & 353 (0.88\%) \\
2 (30) & 40 & 30 (74\%) & 250 (0.63\%) \\
2 (30) & 40 & 30 (76\%) & 134 (0.33\%) \\
2 (30) & 40 & 29 (74\%) & 87 (0.22\%) \\
2 (30) & 40 & 27 (68\%) & 73 (0.18\%) \\
2 (30) & 40 & 30 (75\%) & 63 (0.16\%) \\
4 (60) & 79 & 37 (47\%) & 59 (0.15\%) \\
2 (30) & 40 & 20 (50\%) & 25 (0.06\%) \\
2 (30) & 40 & 29 (72\%) & 21 (0.05\%) \\
1 (15) & 20 & 15 (75\%) & 15 (0.04\%) \\ \hline \end{tabular} Constants: beam energy, \(E_{p}\) = 14.7 MeV; beam current, \(I\) = 15 uA; target thickness, \(t_{target}\) = 0.64 mm; theoretical specific activity, \(\mathit{TS4}\) = 40 Ci\(\cdot\)umol\({}^{-1}\). All activities have been decay-corrected to the end-of-bombardment time for each production.  
\end{table} 
Table 3: Results from ten productions of \({}^{89}\)Zr selected for having the highest effective specific activities (sorted from highest to lowest). Figure 5: Distribution of \({}^{89}\)Zr in various components after each production. For each production, the activity in each of the four primary system components was decay-corrected to a common time point (end-of-bombardment in the cyclotron) and calculated as a percentage of the total activity. Displayed here are the average percentages for each component \(\pm\) 1\(\sigma\). \(N\) = 14.  
and the theoretical stopping ranges of protons in Y metal. The former data were accessed through the NNDC database [19] and the latter from calculations performed using the _SRIM_ software [28]. By geometry, we estimated that 37% of the beam was lost on the lid of the target holder, instead of irradiating the exposed Y foil. The reaction rate (\(R\)) was calculated, followed by the activity (\(A\)), using the equation \(A=R(1-e^{-\lambda t})\)[52], where \(\lambda\) is the decay constant for \({}^{89}\)Zr. The predicted values were also used to evaluate the total activity in the automated module as a percentage, also shown in Table 1.  
To confirm the radionuclide purity of the solution in the product vial, gamma spectroscopy was performed. Typically, a short (10 m) scan of a diluted aliquot from the product vial was performed on the same day as each chemical separation, (see spectra in the ESI). For one production, a long (12 h) scan was performed after waiting for several half-lives (\(\sim\)22 days) of \({}^{89}\)Zr to allow it to decay relative to longer-lived potential radiocontaminants, making them easier to detect by gamma spectroscopy. This spectrum indicated a radionuclide purity of \({}^{89}\)Zr equal to 99.998% of total activity (99.95% of total atoms) and identified \({}^{88}\)Zr as the only radiocontaminant. Even though our recovery percentage was less than most other studies, our radionuclide purity was on par with other publications, only one of which had a radionuclide purity \(<\)99%. This is likely because of the minimal overlap of the excitation function for the \({}^{\mathrm{nat}}\)Y(\(p\),\(n\))\({}^{89}\)Zr reaction with other \({}^{\mathrm{nat}}\)Y(\(p\),\(x\)) reactions, especially the \({}^{\mathrm{nat}}\)Y(\(p\),\(2n\))\({}^{88}\)Zr reaction at these irradiation energies. For most productions of \({}^{89}\)Zr in this work, ESA was determined by DFO titration [23]. ESA accounts for the presence of any metal isotope (stable or radioactive) that can be chelated by the selected chelator, in this case, DFO. For each production, the results of the DFO titration were plotted and fit with a sigmoidal dose-response curve to produce an EC50 value (see ESI), which was used to calculate ESA in \(\mathrm{mCi\text{-}\upmu mol}^{-1}\).