Table 1.

Labeling methods.

	Method	Ion exchanger	Elution solution ion exchanger	Buffer	Advantages/limitations	References
1	Fractional elution	_	_	HEPES	(+) No preconcentration is required	4
					(−) Only ∼80% of activity is available for labeling
					(−) Final purification is required
					(−) The final product contains ethanol
2	Anionic method	SAX	∼0.4 ml water	HEPES	(+) The method delivers 68Ga in high chemical purity	5
					(−) Handling with concentrated HCl is necessary
					(−) Final purification is required
					(−) The final product contains ethanol
3	Cationic method (acetone)	SCX	0.5 ml of acetone/HCl	HEPES	(+) The method is well established	6
					(−) Final purification is required
					(−) The final product contains ethanol and other side products
					(±) The method is licensed for Eckert & Ziegler
4	Cationic method (ethanol)	SCX	1 ml of ethanol/HCl	HEPES, ammonium acetate	(+) Because of the low concentration of foreign ions in the reaction mixture, high specific activities are achievable	8–10
					(−) The final product contains ethanol
					(±) The method is licensed for Eckert & Ziegler
5	Combined cationic-anionic method	(1) SCX(2) SAX	(1) 0.4 ml of 4 M HCl(2) ∼0.4 ml of water	HEPES	(+) Because of the low concentration of foreign ions in the reaction mixture, high specific activities are achievable	11,12
					(−) Handling of 7 M HCl is required
					(−) The final product contains ethanol
					(−) Two steps of postprocessing 68Ga eluate are needed
6	Cationic method (NaCl)	SCX	0.5 ml of 5 M NaCl/0.1 M HCl	Ammonium acetate, sodium acetate	(+) No organic solvents are found in the final product	13,14
					(+) High specific activities are routinely achievable
					(±) The reaction mixture usually contains 1 M sodium chloride, which could be disadvantageous for NaCl-sensitive peptides