1: 4,7,13,16,21,24-hexaoxa-1,10-diazabicyclo[8.8.8]hexacosane*(18)FK / water; dimethyl sulfoxide / 0.04 h / 140 °C 2: sodium tetrahydroborate / water / 0.03 h / Solid phase extraction cartridge 3: hydrogen iodide / water / 0.03 h / 60 °C / Solid phase extraction cartridge 4: sodium azide / water / 0.08 h / 60 °C / Solid phase extraction cartridge View Scheme