A novel stability-indicating method development and validation using reverse-phase ultra–high-performance liquid chromatography (RP- UPLC-PDA) technique for quantification of related substances and assay of Formoterol fumarate in its inhalation solut

Abstract Formoterol fumarate (FMTR) is given to treat asthma, pulmonary illness, and bronchospasm. The impurity profiling/related substances UPLC approach for quantification of six FMTR related substances (FMTR-RS-1 to FMTR-RS-6) and FMTR simultaneously in low dosage (10 μg mL −1 ) FMTR inhalation formulation was developed for the first time. Chromatographic separation of FMTR and six FMTR related substances was accomplished on Acquity BEH C18 column. The elution process involved a gradient program with phosphate buffer (pH 2.8) and acetonitrile as solvents of mobile phase at a flow speed of 0.3 mL min −1 . With a 20-min run time, the FMTR and six FMTR-related substances were monitored and quantified at 214 nm. Selectivity, precision, robustness, linearity, ruggedness, sensitivity and accuracy were all evaluated in order to confirm that the procedure satisfied ICH Q2 (R2) criteria. The method revealed good sensitivity with low LOQ values (0.0212–0.0279 μg mL −1 ), better linearity with R 2 of > 0.999, satisfactory recoveries (88.941%–108.251%) in accuracy and less than 5% RSD in precision for FMTR and six FMTR-related substances. FMTR inhalation formulation was stressed under multiple stress conditions, such as heat, oxidation, photolysis, humidity lysis, base hydrolysis, and acid hydrolysis. Importantly, the impurities produced throughout stress investigations did not interfere with the UPLC procedure for FMTR assay, providing great specific outcomes and stability indicating nature. Two stability testing batches of FMTR inhalation formulation were evaluated deploying the newly established UPLC analytical approach. The FMTR-RS-1 was the major impurity identified in both real-time stability samples and all degradation investigations, except oxidation degradation. The established approach revealed its applicability and potential benefits to the pharmaceutical industry by enabling the quality control department to quickly quantify the impurity profile and analyse FMTR in inhalation dosage forms without compromising quality parameters.