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  • Author or Editor: Monika Dąbrowska x
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The epimers of cefaclor have been separated, identified, and analyzed quantitatively by TLC. The stationary phase was silica gel 60 F 254 , modified with β-cyclodextrin, and the mobile phase was chloroform-ethyl acetate-glacial acetic acid-water 4:4:4:1 ( v/v ). Chromatograms were developed at 5°C, dried at room temperature, and analyzed densitometrically at 274 nm, the wavelength of maximum absorption. Under these conditions good separation of the epimers was achieved ( R F 0.26 and 0.33). UV and 1 H NMR spectra were used to identify the epimers. The method is characterized by high sensitivity (LOD 0.24 and 0.27 μg per band for the epimers at R F 0.26 and 0.33, respectively, LOQ of 0.74 and 0.83 μg per band, respectively, and high accuracy (recovery between 100.03 and 100.81%) and precision (RSD from 0.67 to 1.73%).

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A simple, selective, and sensitive thin-layer chromatography (TLC) method is described for the identification and determination of nabumetone in pharmaceutical products. The mobile phase was constituted by the following mixture: n-hexane-chloroform-glacial acetic acid 4:1:1 (ν/ν/ν); and the stationary phase was TLC plate of silica gel 60 F254. The chromatograms were developed and analyzed densitometrically at λ 1 = 270 nm and λ 2 = 330 nm. R F values and UV spectra were used to identify the compounds. The developed method was characterized by high sensitivity (LOD and LOQ (limits of detection and quantitation) from 0.23 μg per band to 1.00 mg per band), high accuracy (recovery about 100%), and good precision ((relative standard deviation, RSD < 2%).

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The stability of cefaclor and its inclusion complex of β-cyclodextrin was investigated, including an effect of pH solution, temperature, and incubation time. Favorable retention parameters (R F, R s, α) were obtained under developed conditions, which guarantee good separation of studied components. The degradation processes were described with kinetic and thermodynamic parameters (k, t 0.1, t 0.5, and E a). The identification of degradation products was performed with the application of proton nuclear magnetic resonance spectrometry and thin-layer chromatography with densitometry.

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A rapid, accurate, and sensitive densitometric TLC method has been established and validated for simultaneous analysis of eight β-lactam antibiotics (cephalexin, cefadroxil, and cefazolin (first-generation), cefaclor, cefuroxime, and cefuroxime axetil (second-generation), and ceftriaxone and cefotaxime (third-generation)). Chromatographic separation was achieved on silica gel F254 plates with chloroform-ethyl acetate-glacial acetic acid-water 4:4:4:1 (v/v) as mobile phase. Densitometric detection was performed at 275 nm. Statistical evaluation showed the performance of the method was satisfactory. Accuracy was in the range 98.30–100.85% and precision, as RSD, was from 0.4 to 2.45%.

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The application of a simple, selective, precise, and accurate thinlayer chromatographic method for quantification of l-carnitine in dietary food supplements, including drinks, capsules, and tablets, was reported. The high-performance thin-layer chromatography (HPTLC)-cellulose plates as stationary phase, and mixture: methanol-water-glacial acetic acid (10:2:0.1 ν/ν) as mobile phase were chosen. The chromatograms were analyzed densitometrically in the maximum absorption at 420 nm, after ninhydrin-based derivatization reaction. The analytical procedure has been validated in terms of basic parameters, such as linearity, precision, and accuracy. The developed method is characterized by LOD sensitivity of 2.51 μg per spot, as well as LOQ for 7.61 μg per spot and high accuracy established by recovery studies between 99.50% and 103.60 % with good precision (RSD below 1.55%). Presented TLC method illustrated suitability for routine qualitative and quantitative analyses of l-carnitine in dietary supplements.

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A thin-layer chromatographic and densitometric method has been developed for the identification and quantitation of gliclazide and its impurities on silica gel, using chloroform–methanol, 19 + 1 (v/v), as mobile phase. UV densitometric measurements were made at λ = 226 nm. The method is characterized by high sensitivity (15 ng), linearity over a wide concentration range (0.06 to 0.30 mg mL 1), and high recovery (100.23%). It was found that the established conditions can be also used for determination of impurities in medicines.

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A study on the effect of oxidizing or reducing agents on the stability testing of piroxicam, tenoxicam, meloxicam, and isoxicam was performed. Detection of the formed oxidation and/or degradation products after reaction with factors such as iodine, potassium manganate( VII), hydrogen peroxide, and ascorbic acid was conducted by thin-layer chromatography (TLC)—densitometry technique. The reacting mixtures were also exposed to increasing temperatures. The chromatographic profiles showed the formation of several new peaks for all oxicams due to the presence of a number of degradation products formed in the presence of analyzed redox agents. The calculated kinetic parameters have confirmed the greatest stability of meloxicam and piroxicam and the smallest stability of isoxicam in the analyzed conditions. In the case of all the analyzed drugs, principal component analysis identified temperature as the main factor responsible for the speed of degradation and the shape of degradation profile.

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JPC - Journal of Planar Chromatography - Modern TLC
Authors:
Zbigniew Janeczko
,
Jan Krzek
,
Elżbieta Pisulewska
,
Danuta Sobolewska
,
Monika Dąbrowska-Tylka
,
Urszula Hubicka
, and
Irma Podolak

Conditions have been established for identification and quantification of genistin and daidzin in extracts of different soy cultivars by densitometric thin-layer chromatography. Good resolution of the genistin and daidzin peaks was achieved by chromatographic separation on silica gel F 254 HPTLC plates with chloroform-methanol-water, 23 + 8 + 1 ( v/v ), as mobile phase. Under these analytical conditions there was no interference from other extract components.

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The qualitative and quantitative study of the behavior of drugs in various samples, such as pharmaceutical preparations or biological materials, is a significant element from the basis of analysis in the fields of pharmaceutical testing, clinical research, and forensic analysis. A presented thin-layer chromatography (TLC)–densitometry method has been developed for the estimation of cefuroxime axetil and cefepime in human whole blood and urine. Analysis was performed on silica gel 60 F254 TLC plates with two various solvent mixtures as mobile phases. It is a rapid, sensitive, and accurate method for the analysis of drugs from a complex matrix which can be applied in clinical laboratories to monitor the chosen drugs in biological materials.

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polarities was investigated by thin-layer chromatography (TLC)—densitometry in the presence and absence of selected metal ions. It was shown that both solvents and ion type have an effect on the degradation process that leads to the generation of some new products with R F values, which are different from R F values for active substance. It was found that acetone and methanol solutions are sensitive to ultraviolet-C (UV-C) radiation as well as acetone—water and methanol—water solutions for cefepime hydrochloride and cefuroxime axetil. The photostability of cefuroxime axetil after UV-C radiation in acetone solution has the strongest effect on photodegradation compared with the photodegradation carried out in methanol. The studied ions enhanced the degradation of cephalosporins in solutions. Fe(III) and Ni(II) ions exerted the strongest effect on photodegradation of cefepime hydrochloride in acetone compared with radiation carried out in the presence of Mn(II), Cu(II), Co(II), Fe(II), and also without these ions. In methanol solutions of cefepime hydrochloride, a stronger effect on photodegradation was observed by addition of Fe(II) ions. Cefuroxime axetil was more stable in the presence of Fe(II), Fe(III), and Ni(II) in all environments than cefepime hydrochloride. Degradation profiles were additionally compared by principal component analysis to explore the main trends in their shape change.

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