Objective:To establish ion chromatography-suppressed conductivity detection(IC-CD)and high performance liquid chromatography-ultraviolet detection(HPLC-UV)methods to determine the contents of trace nitrite and nitrate in pharmaceutical lactose.LC-MS/MS technology was combined with the con-struction of an online membrane suppression system to confirm the structures.It is to provide new strate-gies for pre-risk control of pharmaceutical lactose.Methods:The high-capacity anion-exchange column of Dionex IonPacTM AS11-HCR FICTM(4.0 mm × 250 mm)and the guard column of Dionex IonPacTM AS11-HCR FICTM(4.0mm× 50mm)were used for both IC-CD and HPLC-UV methods.In the IC-CD method,potassi-um hydroxide solution was applied for gradient elution and the suppressed conductivity cell temperature was 30℃.In the HPLC-UV detection method,the mobile phase was 5 mmol·L-1 sodium hydroxide solution and the detection wavelength was 210 nm.The flow rates and column temperatures of the two methods were set at 1.0 mL·min-1 and 30℃,respectively.The injection volumes were 25 μL.Results:The two determination methods had good linear relationship(r＞0.999)for nitrite in the range of 0.03-10 µg·mL-1,and for nitrate in the range of 0.02-200 μg·mL-1,while the LOD and LOQ were 0.25 ng and 0.75 ng for nitrite,0.25 ng and 0.50 ng for nitrate,respectively.The recoveries were between 84.00％-100.70％.The RSD(n=6)of injection precision were between 0.27％-1.33％.The above results all met the inspection requirements.Conclusion:The two methods have high sensitivity,excellent specificity,good separation and simple pre-processing,which can characterize the contents of trace nitrite and nitrate in pharmaceutical lactose,and also provides new ideas and references for pre-risk study of other pharmaceutical excipients.
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