Development of spectrofluorimetric method for determination of certain antiepileptic drugs through condensation with ninhydrin and phenyl acetaldehyde.

A new and simple spectrofluorimetric method was developed and validated for determination of gabapentin and pregabalin in their pure forms and pharmaceutical formulations with high sensitivity and selectivity. The proposed method was based on the formation of fluorescent products as a result of condensation reaction of investigated drugs with ninhydrin and phenyl acetaldehyde in Teorell and Stenhagen buffer medium. The fluorescent products had emission maxima at 470 nm after excitation at 375 nm. Parameters affecting the progress of the reaction and stability of the formed products were carefully investigated individually and optimized. The fluorescence-concentration plots were rectilinear over the range of 5.0-25.0 μg ml for gabapentin and 2.0-30.0 μg ml for pregabalin with excellent correlation coefficients (0.9999 for gabapentin and pregabalin). The lower detection limits were 0.45 and 0.19 μg ml for gabapentin and pregabalin, respectively. The developed method has been validated in respect to linearity, accuracy, precision, selectivity and sensitivity. In addition, the proposed method was further applied for quantitative analysis of drugs in their pharmaceutical formulations with high degree of accuracy and precision. The obtained results had an excellent agreement with the reference method, indicating no significant difference in accuracy and precision.