Objective        To develop a high performance liquid chromatography (HPLC) method to analyze the content of norepinephrine bitartrate in Norepinephrine Bitartrate Injection

and study the content changes of the injection after exposure to γ-ray irradiation at different intensities.       Methods        Norepinephrine Bitartrate Injection of the same batch was under the exposure to

60

Co-γ ray radiation at 1

2

4

8

16

and 25 kGy by one time. After that

0.14% heptanesulfonic acid sodium salt solution (pH value adjusted to 3.0 by using phosphate): methanol (65∶35) as mobile phase

flow

rate 1 ml/min

detection wavelength 286 nm

injection volume 20 μl were used to determinate the norepinephrine bitartrate content.       Results       The linear range of norepinephrine bitartrate was 5 to 25 μg/ml (r=0.999 9). the yield rates at low

medium and high concentrations of norepinephrine bitartrate (8

10 and 12 μg/ml) was 99.685%

96.366%

and 97.557%

respectively. The inter-day (n=3) and intra-day precision (n=3) were less than 2%. The appearance and clarity of the Injection had no significant change

but the content of norepinephrine bitartrate was decreased in an irradiation dose-dependent manner (P0.05). Especially

when the dose was above 8 kGy

and the content was even lower than the range of acceptable quality.       Conclusion        Our developed HPLC method can be used to determine the active ingredient content in Norepinephrine Bitartrate Injection. Irradiation has a significant impact on the stability of Norepinephrine Bitartrate Injection.