The lipophilicity is an important parameter that influences the activity of the drugs in the human body. The reversed phase high performance thin layer chromatography was applied to determine the Log P values of ibuprofen, ketoprofen, naproxen, and flurbiprofen. The stationary phase used in the study was silica-gel coated plates. The mobile phase was the mixture of acetonitrile and water in different proportions. The content of acetonitrile varied in 5% increments from 50% to 80%. The Rm0 values were determined for the compounds with a known Log P and for the analyzed substances (ibuprofen, naproxen, ketoprofen, and flurbiprofen). The Log P values were calculated for the analyzed compounds using the regression curve Rm0 = f(Log P) parameters for the compounds with the known lipophilicity. Flurbiprofen is characterized by the highest Log P value: 3.82. The lowest one is noted for ketoprofen: 2.66. The determined Log P values of tested compounds were similar to the values calculated by the software.
Box-Behnken Design is a useful tool for the optimization of the chromatographic analysis. The goal of this study was to select the most significant factors that influenced the following parameters of the chromatographic separation: retention time, relative retention time, symmetry of the peaks, tailing factor, a number of theoretical plates, Foley – Dorsey parameter, resolution factor, peak width at half height. The results underwent the ANOVA test to find the statistically significant variables and interactions between them. The level of significance was for p < 0.05. The polynomial equations described quantitatively the statistically significant parameters and the interactions between them. The statistical analysis indicated both the best conditions for the separation of the compounds and the variables that were most influential for peaks’ parameters. The four-factor analysis performed for LEVO and MOXI indicated that ACN, TEA and pH are the most significant factors that influence the separation. The analysis for the pair CIPRO and LEVO required six factors. The statistical analysis proved that the most significant factors are ACN, MeOH and TEA. In the separation of these two compounds on the HPLC column, the interaction ACN × MeOH was also significant.
In this paper the decomposition product of levofloxacin was identified. Levofloxacin was dissolved in 0.9% NaCl, 5% glucose, and Ringer’s solution. The solutions were divided into two batches: the first one was exposed to daylight and the second one was protected from it. The solutions were stored at the room temperature. The qualitative analysis of the degradation product was performed using MS and TOF detectors. The quantitative assay was done by a validated HPLC method. Visual inspection and pH assessment were done. Levofloxacin protected from daylight remained stable in 0.9% NaCl, 5% dextrose, and Ringer’s solution. A slight decomposition of the analyte was observed in the solutions exposed to daylight with the fastest decomposition rate in Ringer’s solution as compared with 0.9% NaCl and 5% dextrose solutions. The degradation product of levofloxacin detected with MS was levofloxacin N-oxide. Levofloxacin solutions should be protected from direct daylight to maintain drug stability. Levofloxacin N-oxide is formed regardless of the solvent used.
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