Spectrophotometric Determination of Imipenem in Bulk and Injection Formulations by 1,2 Naphtho Quinone 4- Sulphonic Acid (NQS) Reagent

A simple and cost effective spectrophotometric method is described for the determination of Imipenem (IMP) in pure and pharmaceutical formulations. The method is based on the formation of dark yellow colored chromogen when the drug reacts with 1,2 naphtho quinone 4- sulphonic acid sodium salt (NQS) reagent in alkalline medium. The method involves the addition of excess NQS of known concentration in the presence of 2.0 mL NaOH and the unreacted NQS was determined by the measurement of the λmax 449 nm, which was found to be the most suitable of several tests. This method was applied for the determination of drug contents in pharmaceutical formulations and enabled the determination of the drug in microgram quantities (0.5 to 3.0 mL). No interference is observed from excipients and the validity of the method was tested against reference method. The colored species has an absorption maximum at 449 nm for IMP (Method A) and obeys beer’s law in the concentration range 0.02 – 0.12 mg/mL of IMP. The apparent molar absorptivity is 0.0190 and sandell’s sensitivity is 7x10-4. The slope is 0.2284 ± 0.0118 and intercept of the equation of the regression line is 0.04971 ± 0.02144. The optimum experimental parameters for the reaction have been studied and the validity of the described procedure was assessed. Statistical analysis of the results has been carried out revealing high accuracy and good precision. The proposed method was successfully applied for the determination of IMP in pharmaceutical formulations.

Author(s): K. Raghu Babu, N. Aruna kumari, A. Vasundhara and R. Vijayalakshmi

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