Stability-indicating methods for the determination of lidocaine and prilocaine in presence of their degradation products

Abstract

Four simple, selective and accurate methods were adopted for the quantitative determination of lidocaine (L) and prilocaine (P) in presence of their major degradation products. In the first method, the second (D2) derivative spectrophotometry at 290 nm was used for the determination of lidocaine in presence of its degradation product 2,6-dimethylaniline over concentration range of 2.5-15 µg.ml-1 with mean percentage recovery 99.98±0.96. The second method based on the use of first (D1) and third (D3) derivative specrophotometry at 240 and 251 nm for the determination of prilocaine in presence of its degradation product o-toludine over concentration range of 2.5-15 µg.ml-1 with mean percentage recoveries 99.95±0.40 and 99.87±0.31, respectively. The third method was adopted depending on the application of ratio-specra 1st derivative (1DD) specrophotometry for the simultaneous determination of lidocaine and prilocaine. Lidocaine was determined at 270 and 277 nm over concentration range of 2.5-15 µg.ml-1 with mean percentage recoveries 100.18±0.43 and 100.32±0.35 whereas, prilocaine was determined at 259 and 268 nm over concentration range of 2.5-15 µg.ml-1 with mean percentage recoveries 100.28±0.25 and 100.24±0.21. The fourth method was a spectrodensitometric analysis, which provides the quantitative densitometric evaluation of thin layer chromatograms of lidocaine and prilocaine. They were determied at 220 nm and 237 nm over concentration ranges of 3-15 µg / spot and 0.4-10 and µg / spot with mean percentage recoveries 99.57±0.53 and 99.97±0.76 for lidocaine and prilocaine, respectively. The HPTLC plates were developed in methanol: n-butanol: distilled water: toluene: glacial acetic acid (2: 3: 1: 2: 0.1 v/v) as mobile phase. The proposed methods were checked using laboratory prepared mixtures and were successfully applied for the analysis of the dosage forms.