Nm For Determination Research Articles

A simple and rapid method for identification and determination of cordycepin in Cordyceps militaris by capillary electrophoresis

Cordycepin is the main active metabolite of Cordyceps militaris extracts; according to recent studies it has interesting therapeutic activities. A new capillary electrophoresis (CE) procedure with UV detection at 254 nm for determination of cordycepin was developed and optimized. Optimal conditions found were 20 mM sodium borate buffer with 28.6% methanol, pH 9.5, separation voltage 20 kV, hydrodynamic injection time 10 s and temperature 25 °C. Linearity was found over the 20–100 μg/mL concentration ranges of cordycepin. The developed method has been applied for determination of cordycepin in various pharmaceutical products. A comparison was made between CE and a high performance liquid chromatography (HPLC) method. Both of these methods gave comparable results. The shorter analysis time and low running cost are the main advantages of CE method.

Stability-Indicating Spectrophotometric and Densitometric Methods for Determination of Aceclofenac

ABSTRACTThree methods were developed for the determination of aceclofenac in the presence of its degradation product, diclofenac. In the first method, third-derivative spectrophotometry (D3) is used. The D3 absorbance is measured at 283 nm where its hydrolytic degradation product diclofenac does not interfere. The suggested method shows a linear relationship in the range of 4–24 µg mL−1 with mean percentage accuracy of 100.05±0.88. This method determines the intact drug in the presence of up to 70% degradation product with mean percentage recovery of 100.42±0.94. The second method depends on ratio-spectra first-derivative (RSD1) spectrophotometry at 252 nm for aceclofenac and at 248 nm for determination of degradation product over concentration ranges of 4–32 µg mL−1 for both aceclofenac and diclofenac with mean percentage accuracy of 99.81±0.84 and 100.19±0.72 for pure drugs and 100.17±0.94 and 99.73±0.74 for laboratory-prepared mixtures, respectively. The third method depends on the quantitative evaluation of thin-layer chromatography of aceclofenac using chloroform:methanol: ammonia (48:11.5:0.5 v/v/v) as a mobile phase. Chromatograms were scanned at 274 and 283 nm for aceclofenac and diclofenac, respectively. The method determined aceclofenac and diclofenac in concentration ranges of 2–10 and 1–9 µg spot−1 with mean percentage accuracy of 100.20±1.03 and 100.14±0.98 for pure drugs and 99.77±0.74 and 100.07±0.78 for laboratory-prepared mixtures, respectively. This method retains its accuracy in the presence of up to 80% degradation product for the studied drug.The suggested procedures were checked using laboratory-prepared mixtures and were successfully applied for the analysis of their pharmaceutical preparation. The validity of the proposed methods was further assessed by applying a standard addition technique. The obtained results agreed statistically with those obtained by the reported method.

Determination of 2,3-benzodiazepine derivatives in rat plasma by high-performance liquid chromatography

A simple high-performance liquid chromatographic method with ultraviolet detection at 240 nm for determination of a novel AMPA/kainate antagonist 1-(4′-aminophenyl)-3,5-dihydro-7,8-dimethoxy-2,3-benzodiazepine (2,3-BZ 6), and its derivatives in rat plasma is described. The procedure involves a fast extraction of the drugs from the plasma spiked with an internal standard. The samples are applied to a pre-packed glass column and drugs are eluted using ethyl acetate. A linear response was observed over the examined concentration range. The lower limit of detection of 2,3-BZ 6 was 5.5 ng/ml. The assay has been used to determine the time course of plasma levels of the 2,3-benzodiazepine derivatives in Sprague–Dawley rats.

Bioelectrochemical monitoring of phenols and aromatic amines in flow injection using novel plant peroxidases.

An amperometric flow system combined with a glucose oxidase-mutarotase reactor was optimized and used to determine aromatic amines and phenols using peroxidase-modified graphite electrodes. An increase in currents upon injection of the analyzed substrate was shown to be approximated by a Michaelis-Menten type dependence. The detection limit was calculated as 3 times the noise, and the sensitivity was calculated as Imax/K(m)app. Commercially available horseradish peroxidase was compared with tobacco anionic and peanut cationic peroxidases for determination of aromatic amines and phenols. Detection limits of 10 nM for determination of o-aminophenol and o- and p-phenylenediamine achieved with a tobacco peroxidase-modified electrode give a promise for further improvements in sensitivities and detection limits of biosensors.

Degradation pathway of quinolines in a biofilm system under denitrifying conditions

AbstractThis article reports for the first time the degradation pathways of quinoline, isoquinoline, and methylquinolines by a mixed culture in a biofilm under nitrate‐reducing conditions. A simple reverse‐phase high‐performance liquid chromatography method using ultraviolet detection at 223 nm for determination of seven quinoline analogues and 15 metabolites was developed, and gas chromatography–mass spectrometry and thin‐layer chromatography analyses were used for identification. The inhibition of nitrification by the parent compounds and their degradation products was assessed by a nitrification toxicity test called MINNTOX. Quinoline and 3‐, 4‐, 6‐, and 8‐methylquinoline were all transformed by hydroxylation into their 2‐hydroxyquinoline analogues (2‐quinolinones), and isoquinoline was transformed into 1‐hydroxyisoquinoline. 2‐Methylquinoline was not transformed by this microcosm, likely due to the blockage at position 2 by the methyl group. The hydroxylated metabolites of isoquinoline and quinolines methylated at the heterocyclic ring were not transformed further, whereas metabolites of quinoline and quinolines methylated at the homocyclic ring were hydrogenated at position 3 and 4, and the resulting 3,4‐dihydro‐2‐quinolinone analogues accumulated. Of these metabolites, only 3,4‐dihydro‐2‐quinolinone from the degradation of quinoline was further transformed into unidentified products. All quinolines and their metabolites had inhibiting effects on the nitrifying bacteria at the same level (ppm) in the applied bioassay, indicating that the inhibition of the compounds was not influenced by the initial transformation reactions.

Simultaneous determination of GTS-21 and its metabolite in rat plasma by high-performance liquid chromatography using solid-phase extraction.

It has been suggested that GTS-21 can improve the learning deficits and inhibit the neuro-degeneration in patients with Alzheimer's disease. This paper describes a reversed-phase high-performance liquid chromatographic assay with visible detection at 405 nm for determination of GTS-21 and its metabolite, 4-hydroxy-GTS-21 in rat plasma. The method uses solid-phase extraction with a Bond Elut C18 column. A quantitation limit of 1.0 ng/ml was achieved using 0.5 ml of rat plasma. In the validation study, the coefficients of variation and the relative errors of each compound were less than 10%. Also freeze-thaw and storage stability were confirmed. This method has proved to be applicable to the pharmacokinetic study of GTS-21 in rats.

Simultaneous determination of benomyl and morestan residues in waters by synchronous solid-phase spectrofluorimetry

In this paper a new, sensitive, and simple method for simultaneous determination of pesticides morestan and benomyl at trace levels in waters is reported. Both chemicals, showing native fluorescence in solution at neutral medium, were fixed on C-18 silica gel at pH 1, giving a fluorescent system. The benomyl-morestan-silica gel system, after dry, was packed in a 1-mm silica cell and its synchronous fluorescence spectra were recorded at δλ=80 nm for determination of benomyl and δλ=25 nm for determination of morestan. Measurements of fluorescence were performed at λ1=289 nm and λ2=367 nm for benomyl and morestan analysis, respectively. The applicable concentration ranges were from 0.5 to 15.0 ng·ml(-1) for benomyl and from 0.6 to 15.0 ng·ml(-1) for morestan, with relative standard deviations of 1.2 and 1.5% for benomyl and morestan, respectively, being 0.15 and 0.18 ng·ml(-1) its respective detection limits. The method was applied to the simultaneous determination of residues of both pesticides in water of different provenances.

An absolute method for protein determination based on difference in absorbance at 235 and 280 nm

Because of the importance of quantitative determination of protein in the research laboratory as well as in the food and feed industries (1), search for the ideal method continues unabated after many years. Methods available include nitrogen determination (Kjeldahl (2) and Dumas (3)), hydrolysis of the protein, derivatization of the amino acids with phthalaldehyde and fluorescence determination (4), determination of bound or free lysine (5) or glutamate (4), and the Lowry (6), biuret (7) dye-binding (8–11) turbidity (12) and spectral methods (13). With the exception of the spectral methods, the methods involve destruction of the sample. In this paper we report the use of difference in absorbance between 235 and 280 nm for determination of protein concentration.

The standardisation of methyl orange albumin methods

Because of the importance of quantitative determination of protein in the research laboratory as well as in the food and feed industries (1), search for the ideal method continues unabated after many years. Methods available include nitrogen determination (Kjeldahl (2) and Dumas (3)), hydrolysis of the protein, derivatization of the amino acids with phthalaldehyde and fluorescence determination (4), determination of bound or free lysine (5) or glutamate (4), and the Lowry (6), biuret (7) dye-binding (8–11) turbidity (12) and spectral methods (13). With the exception of the spectral methods, the methods involve destruction of the sample.In this paper we report the use of difference in absorbance between 235 and 280 nm for determination of protein concentration.