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
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 (λmax of GABA) and 241 nm (λmax 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