Chemistry
I've finsihed my M.Sc. thesis in Analytical Chemistry on Feb. 2001, below is an abstract of my thesis
Abstract
Aim of the Work
Several procedures were published for the determination of Prilocaine using chromatographic methods, on the other hand, a little attention has been paid for the spectrophotometric and electroanalytical methods for the determination of Prilocaine particularly, and local anesthetics in general.
The aim of the work is to develop a new, sensitive and direct method for the determination of Prilocaine in pharmaceutical formulations, using extractional spectrophotometry, and Differential-pulse adsorptive cathodic stripping voltammetry (DP-AdCSV) methods.
Spectrophotometric Method
The absorption spectra of Prilocaine with BTB and BCG were studied in the wavelength range 350-650 nm for solutions prepared according to the recommended procedures. The BTB-Prilocaine and BCG-Prilocaine ion-pairs exhibit absorbance maxima at 416 and 420 nm, respectively.
To optimize the conditions for determination of Prilocaine, several factors were studied such as the effect of pH, amount of buffer used, time of equilibrium, reagent concentration, type of organic solvent, amount of dye, shaking time and number of extractions.
The calibration graphs were plotted under the optimum conditions recommended in the general procedures. The relation between the absorbance of the complex and Prilocaine concentration obey Beer’s law over the concentration range 2.0 – 24.5 ppm using BTB, and 2 – 26.5 ppm using BCG.
Voltammetric Method
It was found that Prilocaine exhibit a voltammetric peak at –1.2 V in both anodic and cathodic differential-pulse adsorptive stripping voltammetry, as shown in figure (11). It was found that, the height of the cathodic peak is higher than the anodic one, hence, differential-pulse adsorptive cathodic stripping voltammetry ( DP-AdCSV) was used during this workIn order to optimize the experimental conditions for the voltammetric determination of Prilocaine, various conditions have been tested such as: effect of pH, accumulation potential, accumulation time, scan rate, pulse amplitude, drop size, and cyclic voltammetric behavior.
The quantitative evaluation was based on the linear correlation between the peak current and Prilocaine concentration. The optimum conditions were found to be: BR buffer (pH=10.5), accumulation potential –0.7 V, accumulation time of 0, scan rate 20 mV/sec, pulse height 50 mV at 0.2 sec pulse interval and medium drop size.
Analytical Application
The validity of the proposed method was investigated for the determination of Prilocaine using the commercially available EMLAR cream (Astra-France).
Exactly 1.0 gm of the cream was dissolved in distilled water, and the volume was completed to 100 ml, then the Prilocaine concentration was determined using the DP-AdCSV according to the general procedures using the pre constructed calibration curve. The determination repeated for five times, a final recovery of 98.1% was obtained, with an RSD of 0.56%.
A little shift in the potential towards positive direction was observed during the use of the commercial form compared with the standard material.
To download the full M.Sc. thesis, please click here (Pdf file, 1.2 MB)
