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Abstract
□ A simple, selective, and precise stability-indicating reversed-phase liquid chromatographic method has been developed and validated for the determination of the first Food and Drug Administration (FDA) approved fixed-dose combination for both diabetes type II and high cholesterol; sitagliptin phosphate monohydrate (SIT); and simvastatin (SIM) in the presence of acid and alkali degradation products of SIT, and the hydrolytic degradation product of SIM. The method was based on gradient elution on a reversed phase C8 column (250mm×4.6mm, 5 µm)—Zorbax SB using a mobile phase consisting of 0.01M potassium dihydrogen orthophosphate (pH=2.6) and acetonitrile. Quantitation was achieved using UV detection at 210nm for SIT and its degradation products, while quantitation of SIM and its degradation product was achieved using UV detection at 240nm. Linearity, accuracy, and precision were found to be acceptable over the concentration ranges of 0.5–200µ g mL −1 and 0.5–100 µ g mL −1 for SIT and SIM, respectively. Limits of detection and quantitation for SIT were found to be 5.65ng and 17.12ng, respectively, while for SIM were found to be 2.72ng and 8.25ng, respectively. The proposed method was successfully applied to the determination of the cited drugs in bulk and in their combined pharmaceutical preparations.
Notes
a Number of theoretical plates per column.
b USP tailing factor.
c %relative standard deviation.
a Standard deviation of intercept.
b Standard deviation of slope.
c %Relative standard deviation.
a%Relative standard deviation.
a Resolution factor between the drug peak and nearest eluted peak.
a There is no significant difference between the proposed method and the reference methods by using the student's t-test (tabulated = 2.228) and F-value (tabulated = 5.050) at p < 0.05.