Gabapentin determination in human plasma and capsule by coupling of solid phase extraction, derivatization reaction, and UV-Vis spectrophotometry

Gabapentin is an anticonvulsant widely used in the treatment of epilepsy. No peculiar chromophore is available on the gabapentin moiety for direct analysis by absorption spectrophotometry. A sensitive spectrophotometric method for the determination of gabapentin in bulk, pharmaceutical formulations and human plasma has been developed. In this method, gabapentin directly derivatized with vanillin and analyzed without any extraction in bulk and pharmaceutical dosage form and in plasma samples, it was extracted with a reversed-phase solid-phase extraction [SPE] cartridge followed by derivatization with vanillin. Analysis was performed by a spectrophotometer system. The quantitation limit of gabapentin in human plasma was 0.8 mg/L. The method was linear over the concentration range of 10.0-90.0 mg/L and 0.8-10.0 mg/L for pharmaceutical dosage form and plasma, respectively. The method was precise [relative standard deviation, RSD <1.20%] and accurate [relative mean error <5.5%] for both pharmaceutical dosage form and plasma samples. Mean absolute recoveries were 94.5% for plasma

Derivative spectrophotometry for simulataneous analysis of chlorpheniramine maleate, phenylephrine HCI, and phenylpropanolamine HCI in ternary mixtures and pharmaceutical dosage forms

In this study, different derivative spectrophotometric methods are proposed for the simultaneous determination of chlorpheniramine maleate [CP], phenylephrine HCl [PE] and phenylpropanolamine HCl [PP] in their ternary mixtures and in pharmaceutical dosage forms. Spectra of single component and ternary mixtures of various concentrations and combinations from zero- to fourth-derivation were obtained. Also the spectra of the excipients including lactose, starch, and microcrystalline cellulose were obtained to study the possible interference from matrices. Zero-crossing derivative spectrophotometry based on recording the second-derivative curve for PE at 286.5 nm and fourth-derivative curve for PP at 220 nm were used for determining each component. Third component, CP, was determined by measuring absolute amplitudes at 265.8, 262.2, 269.5, and 273.8 nm in its second derivative spectra. Results showed that the matrices have no interferences. The calibration curves were linear in the range of 1-8 micro g/ml for PE; 5-30 micro g/ml for PP; and 2-8 micro g/ml for CP. The limits of detection were 0.2 micro g/ml for PE, 0.1 micro g/ml for PP, and 0.3 micro g/ml for CP. The mean percentage recoveries obtained for different synthetic mixtures by using this method were 95.3% with coefficient of variation of 4.3% for PE, 101.5% with coefficient of variation of 1.4% for PP, and 99.4% with coefficient of variation of 1.5% for CP. This method has been applied successfully for the determination of PE and PP in its combination with CP in Antihistamine Decongestant tablets with a high percentage of recovery, good accuracy and precision