Determination of related substances in eldecalcitol soft capsules by solid phase extraction-HPLC
Objective:To establish an amino solid-phase extraction-HPLC method for the determination of three related substances in eldecalcitol soft capsules.Methods:The eldecalcitol soft capsules were extracted by an amino solid-phase extraction method,followed by eluting with ethyl acetate:n-hexane and anhydrous etha-nol.The residue was then dissolved with acetonitrile and water after vacuum evaporation.An ODS column(250 mm×4.6 mm,5 μm)was used.Water-acetonitrile with gradient elution was employed.The flow rate was 1.0 mL·min-1,the injection volume was 50 μL,and the detection wavelength was set at 265 nm.Results:Interference from blank excipients was eliminated with pretreatment.Baseline separation and good selec-tivity of eldecalcitol and other impurities was achieved.The stability of the test and reference solution was investi-gated at 4 ℃.The area change percentage of the impurities in the test solution were 98.6％-102.3％at 24 h.The area change percentage of the impurities in the reference solution were 101.2％,96.9％,98.5％and 96.2％at 24 h,respectively.The quantitation limits of eldecalcitol,trans impurity,pre-eldecalcitol and tachy impurity were 0.107 μg·mL-1,0.102 μg·mL-1,0.128 μg·mL-1 and 0.063 μg·mL-1,respectively.The detection limits were 0.054 μg·mL-1,0.051 μg·mL-1,0.064 μg·mL-1,0.031 μg·mL-1,respectively.The linear ranges of 4 components were 0.1-6.3 μg·mL-,0.1-1.2 μg·mL-,0.1-5.6 μg·mL-and 0.1-1.1 μg·mL-1,respectively.The correlation coefficients(n=5)were 0.999 9,1.000,1.000 and 0.999 4,respectively.The average recoveries(n=6)of tachy impurity,pre-eldecalcitol and trans impurity were 106.6％,88.6％and 102.8％with RSDs of 6.7％,3.1％and 2.1％,respectively.In the three batches of samples,no impurities were detected except pre-eldecalcitol.The contents of pre-eldecalcitol were 5.0％,5.0％and 5.1％,respectively.Conclusion:The method is simple to operate,economical and practical with high safety,strong specificity,good repeatability and high accuracy.The method provides a reliable basis for the study of drug quality such as eldecalcitol soft capsules and drugs with similar oily substrate.
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