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  • Author or Editor: Jan Krzek 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 chromatographic-densitometric method has been established for identification and quantification of S -(+)-2-(6-methoxy-2-naphthyl)propionic acid ( S -(+)-naproxen) and naproxen methyl ester in pharmaceutical preparations. The chromatographic separation was performed on silica gel F 254 TLC plates with cyclohexane-chloroform-methanol, 12 + 6 + 1 ( v/v ), as mobile phase. UV densitometric detection was performed at λ = 223 nm. The method is highly sensitive; the limit of detection for naproxen is 30 ng. Recovery was satisfactory at 95.4%, response was linearly dependent on quantity over a wide range, from 0.0015% to 0.0060%, and repeatability was also satisfactory. The effect of pH, temperature, and incubation time on the degradation of naproxen was investigated.

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A chromatographic-densitometric method has been established for identification and quantitation of selected beta-adrenergic-blocking agents in pharmaceutical preparations. Retention factors, R F , and characteristic absorption spectra of 11 drugs chromatographed on silica gel 60 F 254 HPTLC plates with six mobile phases were used for identification. Quantitation and validation of the method was performed for atenolol, acebutolol, propranolol, and bisoprolol using chloroform-methanol-ammonia, 15 + 7 + 0.2 ( v/v ), as mobile phase. UV densitometric measurements were performed at the wavelength of maximum absorption. Pharmaceutical preparations used in medicine and from a variety of manufacturers were analyzed and the method shown to be sufficiently sensitive for analysis of these samples. The limits of detection and determination ranged from 30 to 400 ng and recovery was from 97.14 to 102.18%. The precision of the method, described by the equation y = x mean ± 2 S , is good and the range of linearity is wide — from 0.020 to 0.250% for individual constituents.

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A densitometric TLC method has been developed for identification and quantification of fluoxetine and its impurities — (1 RS )-3-methylamino-1-phenylpropan-1-ol, N -methyl-3-phenylpropan-1-amine, and C-1, the last of which has not previously been analyzed. The compounds were separated on silica gel 60 F 254 HPTLC plates, with chloroform-methanol-25% ammonia, 45 + 4.5 + 0.5 ( v/v ), as mobile phase. UV and visible densitometric scanning were performed at λ = 260 and 530 nm, respectively, after visualization of the chromatograms with ninhydrin solution. The method enables good separation of the constituents ( R F = 0.20, 0.41, 0.52, and 0.67) with sufficiently high detection limit and recovery for the individual constituents.

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A TLC-densitometric method has been established for determination of impurities in chlorpromazine hydrochloride, trifluoperazine dihydrochloride, promazine hydrochloride, and doxepin hydrochloride. Statistical analysis of the data showed the method is precise and highly sensitive. Results from linear regression analysis of the calibration plots were indicative of good linear relationships over wide ranges of concentration. Application of densitometric UV detection at 254 nm and at the wavelengths of maximum absorbance of the substances resulted in increased detectability of zones in the chromatograms compared with visual inspection under a UV lamp. The conditions described enable objective quantitative evaluation of the limiting concentrations of impurities.

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Ibuprofen is one of the most common nonsteroidal anti-inflammatory and analgesic drugs. It is marked as a racemic mixture though it is known that the pharmacological activity resides in the (+)-(S)-enantiomer only. The process of conversion of (+)-(S)-ibuprofen enantiomer into (−)-(R)-enantiomer, inactive to cyclooxygenase, in methanol and cyclohexane using a chiral selector in TLC separation was investigated. Based on the values of k, t 0.1, and t 0.5, it is shown that the interconversion of (+)-(S) into (−)-(R)-enantiomer runs 10 times faster in polar methanol than in lipophilic cyclohexane.

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A new, simple and rapid thin-layer chromatographic method with densitometric detection has been developed and validated for analysis of oxaprozin and its degradation products. Chromatography was performed on silica gel plates with n -hexane-chloroform-glacial acetic acid 4:1:1 ( v/v ) as mobile phase. Densitometric analysis of oxaprozin was performed in absorbance mode at 286 nm. The method was validated for linearity, accuracy, and precision. Oxaprozin was subjected to acidic and alkaline hydrolysis. The degradation products were well resolved from the pure drug with significantly different R F values. LC-MS-MS analysis revealed that oxaprozin decomposes to produce 1,2-diphenylethanol, 4-iminobutanoic acid, and propan-1-imine.

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A new chromatographic and densitometric method has been established for identification and quantitative analysis of hydrochlorothiazide, triamterene, furosemide, and spironolactone, which are present, together, in complex drugs used to treat hypertension. For separation, silica gel F 254 plates were used with hexane-ethyl acetate-methanol-water-acetic acid 8.4:8:3:0.4:0.2 (v/v) as mobile phase. Densitometric measurements were performed at 264 nm selected for all of the constituents. The method is specific for the analyte constituents examined, and characterized by high sensitivity; LOD is from 0.022 to 0.150 μg per band, LOQ from 0.068 to 0.450 μg per band, recovery from 97.10 to 101.02%, and linear range from 0.060 to 2.650 μg per band. The method is characterized by good precision with RSD from 0.66 to 0.96%.

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A direct, rapid, and sensitive thin-layer chromatography (TLC) method with densitometric detection was developed and validated for the determination of tenoxicam and its degradation products. The chromatographic separation was executed on silica gel TLC 60 F254 plates. Elution was performed with ethyl acetate-toluene-butylamine (2:2:1, ν/ν/ν) as mobile phase. Quantitative analysis was carried out on the basis of the peak areas obtained from reflectance scanning densitometry performed at 288 nm. The method was validated in terms of linearity (35–1820 mg mL−1), accuracy (RSD < 1%), precision (RSD < 2%), sensitivity (LOD = 0.86 mg per band; LOQ = 2.30 mg per band), selectivity, and repeatability. Degradation products were identified by the R F values, absorption spectra, and LC-MS analysis. As the method could effectively separate the drug from its degradation products (i.e., pyridine-2-amine, tiophen), it can be employed as a method to indicate the stability of the compound. Moreover, the proposed TLC method was used to investigate the kinetics of the degradation process.

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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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