## 3 Materials and Methods
### General Information
#### 3.1.2 Spectroscopy  
Nuclear magnetic resonance (NMR) spectra were recorded in a 5% solution at 298 K (\({}^{1}\)H: 400.13 MHz; \({}^{13}\)C: 100.61 MHz; \({}^{19}\)F: 376.49 MHz) using a Bruker Avance Neo 400 (Bruker Bio Spin GmbH, Rheinstetten, Germany). The measured chemical shifts (8) are reported in parts per million (ppm) relative to the residual solvent signals (for CDCl\({}_{3}\), \(\delta_{\rm H}\) = 7.26, \(\delta_{\rm C}\) = 77.16; for DMSO-\(d_{6}\), \(\delta_{\rm H}\) = 2.50, \(\delta_{\rm C}\) = 50.32). The \({}^{1}\)H-NMR spectra are reported as follows: \(\delta\), multiplicity, coupling constant \(J\) (in Hz) where appropriate, number of protons, assignment. The following abbreviations and their combinations are used when reporting NMR data: s = singlet, d = doublet, t = triplet, q = quartet, m = multiplet, s\({}_{\rm br}\) = broad singlet, m\({}_{\rm obsc}\) = obscured multiplet and v = very. NMR signals were assigned based on information from additional two-dimensional experiments (COSY, gHSQC, gHMBC, NOESY). Coupling constants for protons are given in the form of \({}^{n}\)/(\({}^{1}\)H, X), and those for carbons as \({}^{n}\)/(\({}^{13}\)C, \({}^{19}\)F). All \({}^{13}\)C- and \({}^{19}\)F-NMR spectra were recorded under \({}^{1}\)H-broadband decoupling (CPD). Compound names were generated by ChemBioDraw(tm) (CambridgeSoft) following IUPAC nomenclature. The numbering of the benzo[\(d\)]thiazol-2-amine (2-aminobenzo-imidazole) scaffold was performed as shown below.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Parameter** & **Method** & **Unit** & **Specification** & **Result** \\ \hline Appearance & visually & - & clear, no particles & conform \\ Activity concentration at EOS & calculated & MBq/mL & \(\geq\)30 & 172 \(\pm\) 95 \\ Radiochemical identity & HPLC & \% & \(\pm\)5 & 0 \(\pm\) 2 \\ Radiochemical purity & HPLC & \% & \(\geq\)90 & 95.0 \(\pm\) 2.8 \\ Carrier identity & HPLC & \% & \(\pm\)5 & 0 \(\pm\) 2 \\ Carrier concentration & HPLC & \(\mu\)g/mL & \(\leq\)5.0 & 1.12 \(\pm\) 0.48 \\ Total concentration of unknown impurities 1  & HPLC & \(\mu\)g/mL & \(\leq\)5.0 & 0.16 \(\pm\) 0.16 \\ Methanol concentration & GC & mg/mL & \(\leq\)1.0 & 0.06 \(\pm\) 0.03 \\ Ethanol concentration & GC & \%vol & \(\leq\)10 & 9.10 \(\pm\) 0.49 \\ Acetone concentration & GC & mg/mL & \(\leq\)1.0 & n.d. \\ Acetonitrile concentration & GC & mg/mL & \(\leq\)0.41 & n.d. \\ DMSO concentration & GC & mg/mL & \(\leq\)1.0 & n.d. \\ DMA concentration & GC & mg/mL & \(\leq\)1.0 & n.d. \\ pH & indicator & - & 4.5–8.5 & 5.3 \(\pm\) 0.6 \\ \hline \hline \end{tabular}
\end{table}
Table 1: Quality control parameters of the final [1\({}^{1}\)C]tzoadenant tracer formulation.  
Low-resolution mass spectra were obtained in electrospray ionization (ESI-positive) with a Thermo Fischer Scientific MSQ Plus mass spectrometer (Thermo Fisher Scientific GmbH, Dreieich, Germany). The analytes were dissolved in MeOH (about 1 mg/mL) and injected directly through a valve on the ionisation interface. The flow rate of the eluent (MeOH/water/AcOH, 50/50/0.2, \(v/v/v\)) was 200 \(\mu\)L/min. Reported are the \(m/z\)-values of the pseudo-ion [M + H]\({}^{+}\).  
High-resolution mass spectra were determined in the Central Division of Analytical Chemistry at the Forschungszentrum Julich. Elemental analyses were performed using HEKtech GmbH (Wegberg, Germany). Analyses indicated by the symbols of the elements are within \(\pm\)0.4% of the theoretical values.