According to the United States Pharmacopeia and the National Formulary (USP 41-NF 36*) and the European Pharmacopoeia (EP 8.4*), analysis impurity I in formoterol fumarate should meets following requirements. The Asahipak ODP-50 4D (USP-NF L67 equivalent column) confirmed the requirements were met.

System suitability requirements:
   Peak-to-valley ratio **: ≥ 2.5
   Relative retention times for formoterol fumarate and impurity I: 1.0 and 1.17

*The version at the time of the application acquisition. 
**The ratio of the height of impurity I peak to the height of the valley between formoterol fumarate peak.


Sample : 20 µL
 Formoterol Fumarate Resolution Mixture RS
(Mixture of formoterol and formoterol related compound I) 0.1 mg/mL (in H₂O)

Column       : Shodex Asahipak ODP-50 4D (4.6 mm I.D. x 150 mm)
Eluent       : (USP) 4.2 g/L Tribasic potassium phosphate aq. (pH12.0 adjusted with H3PO4)
                     /CH3CN=88/12
               (EP) 5.3 g/L Tribasic potassium phosphate aq. (pH12.0 adjusted with H3PO4)
                    /CH3CN=88/12
Flow rate    : 0.5 mL/min
Detector     : UV (225 nm)
Column temp. : Room temp. (25 °C)

*After analysis, please replace in-column solvent 
 with the shipping solvent and store the column.