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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.


Limiting logarithmic plots for the molar reactivity of PG with the two proposed reagents. (A) log A vs log [reagent] with [PG] kept constant; (B) log A vs log [PG] with [reagent] kept constant.
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Figure 8: Limiting logarithmic plots for the molar reactivity of PG with the two proposed reagents. (A) log A vs log [reagent] with [PG] kept constant; (B) log A vs log [PG] with [reagent] kept constant.

Mentions: The stoichiometry of the reactions in the two methods was studied adopting the limiting logarithmic method [34]. The two straight lines were obtained using increasing concentrations of the reagent while keeping the concentration of the drug constant and using increasing concentrations of the drug while keeping the concentration of the reagent constant. Plots of log absorbance versus log [NQS] and log [PG] gave two straight lines, the slopes of which were 0.93 and 1.05 for NQS and PG, respectively (Figure 8). Hence, It is concluded that the reaction proceeds in the ratio of 1:1, confirming that one molecule of the drug condenses with one molecule of NQS.


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)

Limiting logarithmic plots for the molar reactivity of PG with the two proposed reagents. (A) log A vs log [reagent] with [PG] kept constant; (B) log A vs log [PG] with [reagent] kept constant.
© Copyright Policy
Related In: Results  -  Collection

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

Figure 8: Limiting logarithmic plots for the molar reactivity of PG with the two proposed reagents. (A) log A vs log [reagent] with [PG] kept constant; (B) log A vs log [PG] with [reagent] kept constant.
Mentions: The stoichiometry of the reactions in the two methods was studied adopting the limiting logarithmic method [34]. The two straight lines were obtained using increasing concentrations of the reagent while keeping the concentration of the drug constant and using increasing concentrations of the drug while keeping the concentration of the reagent constant. Plots of log absorbance versus log [NQS] and log [PG] gave two straight lines, the slopes of which were 0.93 and 1.05 for NQS and PG, respectively (Figure 8). Hence, It is concluded that the reaction proceeds in the ratio of 1:1, confirming that one molecule of the drug condenses with one molecule of NQS.

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.