Determination of related substances in etimicin sulfate and sodium chloride injection by HPLC- PAD

Objective: To establish an HPLC- PAD method for the determination of the related substances in etimicin sulfate and sodium chloride injection. Methods: The separation was performed on a Welch Ultimate LP- C 18 column( 4. 6 mm × 300 mm,5 μm) and detected by pulsed amperometric detection( PAD) on a gold electrode( diameter: 3 mm). The column temperature was set at 30 ℃. The mobile phase consisted of an aqueous solution containing 0. 2 mol·L- 1trifluoroacetic acid( pH adjusted to 2. 0 with 50% sodium hydroxide solution) and acetonitrile( 928),the flow rate was 1. 0 mL·min- 1. The alkaline solution after column was 0. 5 mol·L- 1sodium hydroxide solution at a flow rate of 0. 5 mL·min- 1. Results: The linear rang of etimicin was 0. 3- 30 μg·mL- 1( r = 0. 9985). The repeatability RSDs( n = 6) of the maximum impurity and total impurities in a sample were 0. 8% and 1. 3%,respectively. The LOD( S / N = 3) and LOQ( S / N = 10) were 2. 5 ng and 7. 5 ng,respectively. The sample solution was stable within 12 h. Conclusion: The method is simple,accurate and sensitive,and suitable for the determination of the related substances in etimicin sulfate and sodium chloride injection.