Sensitive assay procedure for ethambutol hydrochloride via charge transfer complex formation

Area of Science:

• Analytical Chemistry
• Pharmaceutical Analysis
• Spectrophotometry

Background:

• Ethambutol is a crucial first-line antituberculosis drug.
• Accurate quantification of ethambutol in pharmaceutical dosage forms is essential for therapeutic efficacy and patient safety.
• Existing analytical methods may require improvement in sensitivity or applicability to various dosage forms.

Purpose of the Study:

• To develop and validate a sensitive spectrophotometric method for ethambutol determination.
• To investigate the charge transfer complex formation between ethambutol and iodine.
• To apply the developed method for the analysis of ethambutol in commercial tablet formulations.

Main Methods:

• Formation of a charge transfer complex between ethambutol and iodine.
• Spectrophotometric measurement of the complex at specific wavelengths (293 nm and 360 nm).
• Job's plot analysis to determine the stoichiometry of the complex (1:2 drug-iodine ratio).
• Linearity assessment and determination of the optimal concentration range for accurate quantification.

Main Results:

• The charge transfer complex formation was confirmed, showing blue-shifted iodine bands.
• A 1:2 (ethambutol:iodine) stoichiometry was established.
• The method demonstrated excellent linearity (r=0.9998) at 293 nm over a concentration range of 0.25-15 µg/ml.
• The optimal concentration range for high accuracy was determined to be 1.6-5.8 µg/ml.
• Successful application to the analysis of commercial ethambutol tablets.

Conclusions:

• A sensitive and accurate spectrophotometric method for ethambutol quantification has been successfully developed.
• The method is based on the charge transfer complex formed between ethambutol and iodine.
• This technique is suitable for the routine analysis of ethambutol in pharmaceutical preparations, including tablets.