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Transfer of TLC screening methods to quantitative HPTLC–densitometry methods for pharmaceutical products containing amlodipine besylate, cefpodoxime proxetil, cetirizine 2HCl, diclofenac sodium, efavirenz, mefenamic acid, and atovaquone + proguanil HCl

Zeng B., Gu Y., Sherma J.

Acta Chromatographica

2019

Vol. 31, no. 4

246--249

Transfer of seven thin-layer chromatography (TLC) Global Pharma Health Fund E.V. Minilab protocols for screening counterfeit pharmaceutical products in the field to quantitative high-performance TLC (HPTLC)–densitometry methods was performed using a model process published previously. The developed and validated methods for tablets containing amlodipine besylate, cefpodoxime proxetil, cetirizine 2HCl, diclofenac sodium, efavirenz, mefenamic acid, and atovaquone + proguanil HCl involved the use of only relatively inexpensive and nontoxic solvents, Merck KGaA Premium Purity HPTLC silica gel 60 F254 plates, semi-automated sample and standard solution application with a CAMAG Linomat 4, and automated densitometry with a CAMAG Scanner 3 for detection, identification, and quantification. In addition, previously transferred HPTLC–densitometry methods for azithromycin and for cephalexin were used to analyze a new product of each drug to demonstrate the applicability of the methods.

Studies on the Distribution of Mefenamic Acid in Two-Phase Systems: Aromatic Solvent-Water

Zapała L., Kalembkiewicz J., Szlachta J.

Polish Journal of Chemistry

2005

Vol. 79 / nr 7

1235-1244

The detailed description of equilibria of mefenamic acid in the aqueous solutions and in the two-phase systems: aromatic solvent - water was made. Isoelectric point, pHI, dissociation constants of the protonated form,Ka1, and the neutral form,Ka2, in the aqueous solutions were determined. On the basis of the spectrophotometric investigations the values of the distribution ratio, D, of mefenamic acid were obtained. Employing the results of the potentiometric titration in the two-phase systems, organic solvent - water, and using models of singular and multistep equilibrium the values of the partition constants, KD, and dimerization constants, Kd, were calculated. The significant influence of the polarity of the applied organic solvents and of pH of the aqueous phase on the percentage of the particular forms of mefenamic acid in the two-phase systems were proved. Key words: mefenamic acid, liquid-liquid distribution, two-phase systems equilibria