Silica gel itlc

The eluted ⁸⁹Zr(HPO₄)₂ solution (120 μL) was neutralized to pH 7.8 with 100 μL 1 M HEPES-KOH buffer (pH 7.5) and 65 μL 1 M K₂CO₃. To this, 4 μL 5 mM DFO-Bz-NCS in DMSO (Macrocylics, Dallas, TX, USA) was added, and chelation of ⁸⁹Zr⁴⁺ proceeded at 37°C for 1 h in a thermomixer at 550 rpm. Chelation efficiency was determined by silica gel iTLC (Agilent Technologies, Santa Clara, CA, USA) with 50 mM DTPA pH 7 as the mobile phase. ⁸⁹Zr-DBN showed an R_f = 0, whereas ⁸⁹Zr(HPO₄)₂ had an R_f = 0.9.

The ⁸⁹Zr used in this study was produced on a PETtrace cyclotron (GE Healthcare, Waukesha, WI) using ⁸⁹Y target foil (0.1 mm; 50 X 50 mm, 99.9%), which was purchased from Alfa-Aesar, Haverhill, MA. The trace metal grade nitric acid (67–70%) and hydrochloric acid (34–37%) were purchased from Thermo Fisher Scientific, Waltham, MA. Sodium bicarbonate, oxalic acid dehydrate (TraceSELECT^® ≥ 99.9999% metal basis), sodium carbonate, sodium citrate dihydrate and HPLC grade acetonitrile were purchased from Sigma Aldrich, St. Louis, MO. The silica gel iTLC was purchased from Agilent Technologies, Santa Clara, CA. The chelator p-SCN-Bn-Deferoxamine or DFO-Bn-NCS (≥ 94%) was purchased from Macrocylics, Plano, TX, whereas the other two chelators Hy₃ADA⁵-NCS and Hy₃ADA⁵-SA were synthesized as described by Klasen et al.^{66 (link)}. The empty Luer-Inlet SPE cartridges (1 mL) with frits (20 µm pore size) were purchased from Supelco Inc (Bellefonte, PA) and Chromafix^® 30-PS-HCO₃ PP cartridges (45 mg) were purchased from Macherey–Nagel, Duren, Germany. The Millex ^®-GV filter (0.2 µm) was purchased from Millipore Sigma, Burlington, MA. The hydroxamate resin was synthesized in-house as demonstrated by Pandey et al.^{67 (link)–70 (link)} The Thermomixer was purchased from Eppendorf, Hamburg, Germany.