Separation of Radiometals

A method of separation of a radiometal ion from a target metal ion, comprising a first liquid-liquid extraction step in which an organic phase comprising an extractant and an interfacial tension modifier is mixed with an aqueous phase comprising the radiometal ion and the target metal ion in order that the radiometal ion is at least partially transferred to the organic phase, followed by a first phase separation step, wherein the phase separation is carried out in flow comprising the use of a microfiltration membrane to separate the phases based on the interfacial tension between the phases such that a permeate phase passes through the membrane and a retentate phase does not, wherein:

• a. the radiometal ion is a 68Ga ion, the target metal ion is a 68Zn ion, the extractant is selected from one or more dialkyl ethers R1OR2, wherein the two alkyl groups R1 and R2 can be the same or different, or can together form a cyclic ether, and can optionally be substituted, and the interfacial tension modifier is selected from one or more aromatic hydrocarbons, which may optionally be halogenated, and/or one or more C2-C9 alkanes, which may optionally be halogenated;
• or
• b. the radiometal ion is a 89Zr ion, the target metal ion is a natY ion, the extractant is a solvent able to function as a bidentate ligand for 89Zr via two oxygen atoms, and the interfacial tension modifier is a solvent having similar properties to the extractant, but that are not able to function as a bidentate ligand for the 89Zr ion, such that it does not interfere with the ability of the extractant to interact with the 89Zr ions;
• or
• c. the radiometal ion is a 45Ti ion, the target metal ion is a natSc ion, the extractant is a solvent able to function as a bidentate ligand for 45Ti via two oxygen atoms, and the interfacial tension modifier is a solvent having similar properties to the extractant, but that are not able to function as a bidentate ligand for the 45Ti ion, such that it does not interfere with the ability of the extractant to interact with the 45Ti ions;
• or
• d. the radiometal ion is a 64Cu ion, the target metal ion is a 64Ni ion, the extractant is selected from:
• one or more trialkyl phosphine oxides;
• one or more alkylphosphoric acid monoalkyl esters;
• one or more diketones having the structure R3—C(═O)CH2C(═O)—R4, in which R3 and R4 are each independently an alkyl or an aryl group;
• and one or more aldoximes or ketoximes in which the substituent(s) of the oxime group are aromatic groups;
• and the interfacial tension modifier is a solvent comprising one or more straight or branched chain cyclic or acyclic aliphatic alkanes having from five to sixteen carbon atoms, which may optionally be substituted, and/or a solvent comprising one or more aromatic hydrocarbons, which may optionally be substituted.