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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.


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Absorption spectra of (a) NQS 0.5%(w/v) in water (method I). (b) PG (25 μg mL-1) with NQS (method I). (c) DNFB 0.3%(w/v) in methanol (method II). (d) PG (6 μg mL-1) with DNFB (method II).
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Figure 2: Absorption spectra of (a) NQS 0.5%(w/v) in water (method I). (b) PG (25 μg mL-1) with NQS (method I). (c) DNFB 0.3%(w/v) in methanol (method II). (d) PG (6 μg mL-1) with DNFB (method II).

Mentions: 1,2-naphthoquinone-4sulphonate sodium has been used as chromogenic and fluorogenic reagent for the analysis of many pharmaceutical primary and secondary amines [27-29]. However, its reaction with PG has not been yet investigated. Therefore, the present study was devoted to explore NQS as a derivatizing reagent for the development of spectrophotometric method for the determination of PG in its capsules. NQS was found to react with PG in borate buffer of pH 10.5 yielding a highly colored orange reaction product which exhibit maximum absorbance at 473 nm (Figure 2).


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)

Absorption spectra of (a) NQS 0.5%(w/v) in water (method I). (b) PG (25 μg mL-1) with NQS (method I). (c) DNFB 0.3%(w/v) in methanol (method II). (d) PG (6 μg mL-1) with DNFB (method II).
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC3141622&req=5

Figure 2: Absorption spectra of (a) NQS 0.5%(w/v) in water (method I). (b) PG (25 μg mL-1) with NQS (method I). (c) DNFB 0.3%(w/v) in methanol (method II). (d) PG (6 μg mL-1) with DNFB (method II).
Mentions: 1,2-naphthoquinone-4sulphonate sodium has been used as chromogenic and fluorogenic reagent for the analysis of many pharmaceutical primary and secondary amines [27-29]. However, its reaction with PG has not been yet investigated. Therefore, the present study was devoted to explore NQS as a derivatizing reagent for the development of spectrophotometric method for the determination of PG in its capsules. NQS was found to react with PG in borate buffer of pH 10.5 yielding a highly colored orange reaction product which exhibit maximum absorbance at 473 nm (Figure 2).

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.


Related in: MedlinePlus