Mervat M. Hosny

Spectrophotometric and AAS determination of ramipril and enalapril through ternary complex formation.

Two sensitive, spectrophotometric and atomic absorption spectrometric procedures are developed for the determination of two antihypertensive agents (enalapril maleate and ramipril). The spectrophotometric procedures for the two cited drugs are based on ternary complex formation. The first ternary complex (copper(II), eosin, and enalapril) was estimated by two methods; the first depends on its extraction with chloroform measuring at 533.4 nm. Beers law was obeyed in concentration range from 56 to 112 microg ml(-1). The second method for the same complex depends on its direct measurement after addition of methylcellulose as surfactant at the pH value 5 at 558.8 nm. The concentration range is from 19 to 32 microg ml(-1). The second ternary complex (iron(III), thiocyanate, and ramipril) was extracted with methylene chloride, measuring at 436.6 nm, with a concentration range 60-132 microg ml(-1). The direct atomic absorption spectrometric method through the quantitative determination of copper or iron content of the complex was also investigated for the purpose of enhancing the sensitivity of the determination. The spectrophotometric and atomic absorption spectrometric procedures hold their accuracy and precision well when applied to the determination of ramipril and enalapril dosage forms.

Spectrscopic and Conductometric Analysis of Gabapentin

Four simple, sensitive and reproducible methods were developed for the determination of gabapentin (GPT) in pure form and in pharmaceutical preparations. Methods A and B are based on the reaction of cupric chloride with gabapentin to form stable complex, which could be measured spectrophotometrically atmax 246 nm (method A) or by using conductometric technique (method B). While method C and D depends on the formation of ion pair complex between the studied drug and bromothymol blue, bromocresol green respectively this was extractable with methylene chloride. The concentration ranges were 40-95 µg mL -1 , 1-15 mg, 100-800 and 10-150 µg mL -1 for methods A, B, C and D respectively .The optimization of various experimental conditions were described .The results obtained showed good recoveries, Ringbom optimum concentration ranges were calculated, in addition to molar absorptivity and sandells sensitivity, detection and quantification limits. The methods were successfully applied to the determination of GPT in bulk and pharmaceutical preparations. The results were favorably comparable with the official method. The molar combining ratio for methods (A-B) was found to be (2:1) (drug: reagent) while for method (C-D) it was found to be (1:1).