A new stability indicating reverse phase high performance liquid chromatography method for the determination of enantiomeric purity of a DPP-4 inhibitor drug linagliptin.

A simple, sensitive, and stability indicating isocratic reverse phase high performance liquid chromatography method has been developed, optimized and validated for the separation and quantification of S-enantiomer in linagliptin (R-enantiomer) drug substance. Enantiomeric separation was achieved on a Cellulose tris(4-chloro-3-methylphenylcarbamate) stationary phase. Mobile phase consists of aqueous diammonium hydrogen phosphate buffer and acetonitrile in the ratio of 35:65 v/v. Isocratic elution was performed at a flow rate of 1.0 mL/min, the column oven temperature was set at 40°C and detection was at 226 nm. The resolution between R and S enantiomers is found to be more than 4.0. The impact of mobile phase composition, pH of buffer and temperature on the resolution has been studied. The detector response is found to be linear over the concentration range of 0.17-1.7 µg/mL. LOD and LOQ levels of S-enantiomer are found to be 0.057 and 0.172 µg/mL respectively. The recovery of S-enantiomer is 99.8% w/w. The proposed method is validated for specificity, precision, linearity, accuracy and robustness.

Atypical carcinoid of larynx: a case study and a brief review.

Atypical Carcinoids, Malignancy arising from neuroendocrine cells are among the non-Epidermoid cancers of larynx.The present study reports an interesting and rare case of atypical carcinoid of larynx. An 85-year-old male patient presented with a history of dysphagia.On clinical examination, a provisional diagnosis of cyst larynx was made. But during surgery, the Diagnosis had to be reviewed as benign lesion of the larynx. Histopathological diagnosis was atypical carcinoid. The present study discusses the unusual presentation and unusual clinical diagnosis of these neuroendocrine neoplasms of larynx.