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Utility of certain nucleophilic aromatic substitution reactions for the assay of pregabalin in capsules.

Walash MI, Belal FF, El-Enany NM, El-Maghrabey MH - Chem Cent J (2011)

Bottom Line: The developed methods were successfully applied to the analysis of the drug in its commercial capsules.Statistical analysis of the results revealed good agreement with those given by the comparison method.Proposals of the reaction pathways were postulated.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Analytical Chemistry, Faculty of Pharmacy, University of Mansoura, 35516, Mansoura, Egypt. nelenany1@yahoo.com.

ABSTRACT

Background: Pregabalin (PG) is an anticonvulsant, analgesic and anxiolytic drug. A survey of the literature reveals that all the reported spectrophotometric methods are either don't offer high sensitivity, need tedious extraction procedures, recommend the measurement of absorbance in the near UV region where interference most probably occurs and/or use non specific reagent that don't offer suitable linearity range.

Results: Two new sensitive and simple spectrophotometric methods were developed for determination of pregabalin (PG) in capsules. Method (I) is based on the reaction of PG with 1,2-naphthoquinone-4-sulphonate sodium (NQS), yielding an orange colored product that was measured at 473 nm. Method (II) is based on the reaction of the drug with 2,4-dinitrofluorobenzene (DNFB) producing a yellow product measured at 373 nm. The different experimental parameters affecting the development and stability of the reaction product in methods (I) and (II) were carefully studied and optimized. The absorbance-concentration plots were rectilinear over the concentration ranges of 2-25 and 0.5-8 μg mL-1 for methods (I) and (II) respectively. The lower detection limits (LOD) were 0.15 and 0.13 μg mL-1 and the lower quantitation limits (LOQ) were 0.46 and 0.4 μg mL-1 for methods (I) and (II) respectively.

Conclusion: The developed methods were successfully applied to the analysis of the drug in its commercial capsules. The mean percentage recoveries of PG in its capsule were 99.11 ± 0.98 and 100.11 ± 1.2 (n = 3). Statistical analysis of the results revealed good agreement with those given by the comparison method. Proposals of the reaction pathways were postulated.

No MeSH data available.


Effect of the volume of reagent on the absorbance of the reactions products of PG with NQS or DNFB.
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Figure 5: Effect of the volume of reagent on the absorbance of the reactions products of PG with NQS or DNFB.

Mentions: The influence of the reagents concentration was studied using different volumes of either 0.5% w/v solution of NQS (Method I) or 0.3% v/v solution of DNFB (Method II). It was found that, increasing volumes of the reagents produced a proportional increase in the absorbance values. Maximum absorbencies were achieved using volumes of the reagents ranged from 0.7-2.0 or 0.4-1.0 mL of NQS or DNFB for Methods I and II, respectively. Further increase of the reagents volume produced a gradual decrease in the absorption intensity. Therefore, 1 mL of 0.5% w/v NQS solution and 0.6 mL of 0.3% v/v DNFB solution were chosen as the optimal volumes of the reagents for Methods I and II, respectively (Figure 5). For Method II, to remove the excess DNFB reagent interference in the absorbance measurement of the reaction product, this excess was acid-hydrolyzed to colorless 2,4-dinitrophenol by adding 0.2 mL of HCl allowing the measurement of PG-DNFB derivative which remains stable.


Utility of certain nucleophilic aromatic substitution reactions for the assay of pregabalin in capsules.

Walash MI, Belal FF, El-Enany NM, El-Maghrabey MH - Chem Cent J (2011)

Effect of the volume of reagent on the absorbance of the reactions products of PG with NQS or DNFB.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3141622&req=5

Figure 5: Effect of the volume of reagent on the absorbance of the reactions products of PG with NQS or DNFB.
Mentions: The influence of the reagents concentration was studied using different volumes of either 0.5% w/v solution of NQS (Method I) or 0.3% v/v solution of DNFB (Method II). It was found that, increasing volumes of the reagents produced a proportional increase in the absorbance values. Maximum absorbencies were achieved using volumes of the reagents ranged from 0.7-2.0 or 0.4-1.0 mL of NQS or DNFB for Methods I and II, respectively. Further increase of the reagents volume produced a gradual decrease in the absorption intensity. Therefore, 1 mL of 0.5% w/v NQS solution and 0.6 mL of 0.3% v/v DNFB solution were chosen as the optimal volumes of the reagents for Methods I and II, respectively (Figure 5). For Method II, to remove the excess DNFB reagent interference in the absorbance measurement of the reaction product, this excess was acid-hydrolyzed to colorless 2,4-dinitrophenol by adding 0.2 mL of HCl allowing the measurement of PG-DNFB derivative which remains stable.

Bottom Line: The developed methods were successfully applied to the analysis of the drug in its commercial capsules.Statistical analysis of the results revealed good agreement with those given by the comparison method.Proposals of the reaction pathways were postulated.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Analytical Chemistry, Faculty of Pharmacy, University of Mansoura, 35516, Mansoura, Egypt. nelenany1@yahoo.com.

ABSTRACT

Background: Pregabalin (PG) is an anticonvulsant, analgesic and anxiolytic drug. A survey of the literature reveals that all the reported spectrophotometric methods are either don't offer high sensitivity, need tedious extraction procedures, recommend the measurement of absorbance in the near UV region where interference most probably occurs and/or use non specific reagent that don't offer suitable linearity range.

Results: Two new sensitive and simple spectrophotometric methods were developed for determination of pregabalin (PG) in capsules. Method (I) is based on the reaction of PG with 1,2-naphthoquinone-4-sulphonate sodium (NQS), yielding an orange colored product that was measured at 473 nm. Method (II) is based on the reaction of the drug with 2,4-dinitrofluorobenzene (DNFB) producing a yellow product measured at 373 nm. The different experimental parameters affecting the development and stability of the reaction product in methods (I) and (II) were carefully studied and optimized. The absorbance-concentration plots were rectilinear over the concentration ranges of 2-25 and 0.5-8 μg mL-1 for methods (I) and (II) respectively. The lower detection limits (LOD) were 0.15 and 0.13 μg mL-1 and the lower quantitation limits (LOQ) were 0.46 and 0.4 μg mL-1 for methods (I) and (II) respectively.

Conclusion: The developed methods were successfully applied to the analysis of the drug in its commercial capsules. The mean percentage recoveries of PG in its capsule were 99.11 ± 0.98 and 100.11 ± 1.2 (n = 3). Statistical analysis of the results revealed good agreement with those given by the comparison method. Proposals of the reaction pathways were postulated.

No MeSH data available.