The large dead volume found between the adaptors and the solid phase component of the cartridge led to accumulation of the eluent and resulting dilution of the most concentrated fraction. In order to overcome this problem, the dead volume was removed to produce an altered Hypercarb cartridge (Vs2; Fig. ), more suitable for automated purification. For Vs2 assembly details, see Supplemental Fig. . The use of Vs2 resulted in a considerable increase in radiotracer concentration, more than doubling that produced using Vs1 from 10.8 ± 2.32