Determination of Dexamethasone and its organic impurities content as per USP monograph UHPLC method

Importance of the Topic

The accurate determination of dexamethasone content and its organic impurities is essential for ensuring drug safety and efficacy. High-performance chromatographic methods are critical in pharmaceutical quality control to meet regulatory standards and detect trace-level impurities that may affect patient health or product stability.

Study Objectives and Overview

• Evaluate the performance of the Shimadzu Nexera XS UHPLC system for the assay and organic impurity testing of dexamethasone in accordance with the USP monograph.
• Verify compliance with system suitability and acceptance criteria specified by the USP, including reproducibility, resolution, and impurity limits.

Methodology and Instrumentation

The study followed USP monograph procedures for dexamethasone assay and organic impurity analysis. Mobile phase A consisted of potassium phosphate buffer at pH 3.0 and mobile phase B was acetonitrile. Chromatographic separation used a 100 mm × 2.1 mm, 1.7 μm C18 column at 35 °C with a flow rate of 0.4 mL/min and a gradient program over 20 min. Detection was performed at 240 nm. Standard, system suitability, and sample solutions were prepared at specified concentrations and sonicated to ensure complete dissolution.

• Instrumentation: Shimadzu Nexera XS UHPLC system equipped with an autosampler at 10 °C and UV detector set to 240 nm.

Key Results and Discussion

• Assay performance: Dexamethasone eluted at approximately 8.96 min. The relative standard deviation (RSD) for retention time and peak area across replicates was below 0.16 %, and peak tailing remained under 1.8, meeting USP criteria. Measured assay values ranged from 100.7 % to 101.3 %, within the 97.0–102.0 % acceptance range.
• Organic impurities: The resolution between betamethasone and dexamethasone peaks was 1.65 (above the USP minimum of 1.5). RSD values for known impurity peaks were below 5.0 %. Relative retention times for betamethasone, desoximetasone, dexamethasone 7,9-diene and dexamethasone acetate were consistent with USP requirements. Total impurity levels did not exceed 0.5 % and individual impurity responses were within specified limits.
• Several unidentified minor impurities were observed at low levels, all below individual acceptance thresholds, demonstrating the method’s sensitivity.

Benefits and Practical Applications

• Provides a fast, robust, and reproducible UHPLC method for routine quality control of dexamethasone formulations.
• Automation and intelligent diagnostics of the Nexera XS system reduce operator dependency and risk of errors.
• Compliance with USP standards ensures regulatory acceptance for pharmaceutical testing and stability studies.

Future Trends and Potential Applications

Advances in artificial intelligence and Internet of Things integration may enable real-time system monitoring and predictive maintenance. The proven UHPLC method can be extended to other corticosteroids and small-molecule APIs. Miniaturized and high-throughput formats may further enhance laboratory productivity.

Conclusion

The Shimadzu Nexera XS UHPLC system successfully met all USP monograph requirements for dexamethasone assay and organic impurity testing. The method demonstrated excellent reproducibility, sensitivity, and compliance with pharmacopeial criteria, making it well suited for pharmaceutical quality control laboratories.