Concurrent Estimation of Gabapentin and Nortriptyline Hydrochloride in their Combined Dosage Form Using OPA-B -Mercaptoethanol Derivatization by Spectrophotometric and Spectrofluorimetric Methods

Abstract

Background: The proposed manuscript focus on the method development and validation for the estimation of non chromophoric drug by derivatization in combination with other drug. Objective: To develop and validate UV-spectrophotometric and spectrofluorimetric methods for the simultaneous estimation of gabapentin (GABA) and nortriptyline hydrochloride (NTH) in combined dosage form. Method: Most challenging task for the method is derivatization because the GABA lacking in chromophoric group, so derivatization of primary amine with OPA will improve characteristic of compound and it is detected by Spectrophotometric and Spectrofluorimetric techniques. Results: UV Spectrophotometric method includes absorbance correction method at two wavelengths i.e. at 335 nm (max of GABA) and 241 nm ((max of NTH max of NTH) in methanol. Linearity range was observed in the concentration range 160-560 μg/mL with mean recovery of 100.96 % ± 0.67 for GABA and 4-14 μg/mL with mean recovery of 99.73 % ± 0.55 for NTH, respectively. The correlation coefficients for GABA and NTH were found to be 0.9994 and 0.9999, respectively. LOD and LOQ were found to be 2.390 and 7.241 μg/mL for GABA 0.01 and 0.03 μg/mL for NTH, respectively. Spectrofluorimetric method includes synchronous simultaneous equation method for measurement of fluorescence intensity at 417 nm for GABA and 377 nm for NTH in borate buffer. Linearity range was observed in the concentration range 10-90 μg/mL with mean recovery of 100.73 % ± 0.74 for GABA and 0.25-2.25 μg/mL with mean recovery of 100.08 % ± 0.17 for NTH, respectively. The correlation coefficients for GABA and NTH were found to be 0.9989 and 0.9984, respectively. LOD and LOQ were found to be 0.59 and 1.80 μg/mL for GABA and 0.060 and 0.18 μg/mL for NTH, respectively. Conclusion: The validated methods are economic, time saving, sensitive, accurate, and reproducible and can be successfully applied for routine quality control of the GABA and NTH in their combined dosage form.