Response Surface Methodology in Spectrophotometric Estimation of Saxagliptin, Derivatization with MBTH and Ninhydrin

Design of experiments assisted spectrophotometric methods have been established for the quantification of saxagliptin in pharmaceutical formulation via charge transfer complexation and Schiff's base formation.

Box-Behnken design was exploited in method-1, involved the measurement of absorbance of green/blue-colored complex (at 600 nm), formed by the reaction of saxagliptin with 3-methyl-2-benzothiazolinone hydrazone in the presence of ferric chloride. The central composite design was employed in method-2, involved the determination of absorbance of Ruhemann's purple (at 585 nm), formed by the reaction of the primary amine group of saxagliptin with ninhydrin reagent in presence of sodium hydroxide. Optimization of reaction variables namely, reagent concentration (A), oxidizing agent/alkalinity (B) and reaction/heat time (C) was performed through response surface methodology for the response (Y) i.e. absorbance of colored compound. The reliability of both methods was investigated through validation as per International Council for Harmonisation guidelines.

Saxagliptin executed linearity in the concentration range of 0.01-0.25 μg/mL and 1-10 μg/mL by method-1 and 2. A high value of molar absorptivity, low values of Sandell's sensitivity and limit of detection/limit of quantification divulges the good sensitivity methods. The % assay of saxagliptin in the marketed formulation was found to be 100.27 and 99.86 by method-1 and method-2, respectively.

The proposed eco-friendly and economical methods can be routinely employed in quality control for the analysis of saxagliptin in the pharmaceutical dosage forms.