975 resultados para LU-LC Conjecture


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A simple liquid chromatographic method was optimized for the quantitative determination of terbinafine in pharmaceutical hydroalcoholic solutions and tablets, and was also employed for a tablet dissolution test. The analysis was carried out using a RP-C18 (250 mm × 4.6 mm, 5 μm) Vertical® column, UV-Vis detection at 254 nm, and a methanol-water (95:5, v/v) mobile phase at a flow-rate of 1.2 mL min-1. Method validation investigated parameters such as linearity, precision, accuracy, robustness and specificity, which gave results within the acceptable range. The tablets dissolution was quite fast: 80% of the drug was dissolved within 15 min.

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A LC-ESI-MS/MS method was developed and validated according to the European Union decision 2002/657/EC, for the determination of tetracyclines (TCs) in chicken-muscle since Europe is one of the main markets for Brazilian products. Linearity of r > 0.9979, limits of quantification in the range of 7.0-35.0 ng/g, average recoveries of 89.38 - 106.27%, within-day and between-day precision were adequate for all TCs. The decision limit and the detection capability were 93.00-106.46 ng/g and 95.84-114.38 ng/g, respectively. This method is suitable for application in surveillance programmes of residues of TCs in chicken-muscle samples.

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An evaluation of the pesticides extraction from onion using a modern sample preparation method (QuEChERS) and determination by liquid chromatography tandem mass spectrometry was carried out. All the calibration curves showed r>0.99. The recoveries ranged between 61.8 and 120.0% with relative standard deviation lower than 20% for all compounds. Due to the occurrence of matrix effect, the quantification was performed using matrix-matched calibration. The limits of quantification of the method were between 0.0005 and 0.05 mg kg-1. The method shows the advantages of not require the clean-up step and consume low volume of organic solvents, decreasing time, costs and residues.

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An LC-MS/MS method has been developed for the determination of efavirenz (EFZ) in human plasma using hydrochlorothiazide as internal standard (I.S.). An ESI negative mode with multiple reaction-monitoring was used monitoring the transitions m/z 313.88→69.24 (EFZ) and 296.02→204.76 (I.S.). Samples were extracted using liquid-liquid extraction. The total run time was 2.0 min. The separation was achieved with HPLC-RP using a monolithic column. The assay was linear in the concentration range of 100 - 5000 ng mL-1. The mean recovery was 83%. Intra- and inter-day precision were < 9.5% and < 8.9%, respectively and accuracy was in the range ± 8.33%. The method was successfully applied to a bioequivalence study.

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A method using LC/ESI-MS/MS for the quantitative analysis of Ochratoxin A in roasted coffee was described. Linearity was demonstrated (r = 0.9175). The limits of detection and quantification were 1.0 and 3.0 ng g-1, respectively. Trueness, repeatability and intermediate precision values were 89.0-108.8%; 2.4-13.7%; 12.5-17.8%, respectively. To the best of our knowledge, this is the first report in which Ochratoxin A in roasted coffee is analysed by LC/ESI-MS/MS, contributing to the field of mycotoxin analysis, and it will be used for future production of Certified Reference Material.

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A reliable method using LC-UV to assay mometasone furoate (MF) in creams or nasal sprays using the same chromatographic conditions was set up. Methanol:water 80:20 (v/v) (1.0 mL min-1) was used as mobile phase. MF was detected at 248 nm and analyzed in a concentration range from 1.0 to 20.0 µg mL-1. The method provided acceptable theoretical plates, peak simmetry, peak tailing factor and peak resolution a short run (5 min). The method showed specificity, good linearity (r = 0.9999) and the quantification limit was 0.379 µg mL-1. Furthermore, the method was precise (RSD < 2.0%), accurate (recovery > 97%) and robust.

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A stability-indicating method using MEKC was validated for the analysis of olmesartan medoxomil in tablets. Successful separation was achieved using a fused silica capillary (40 cm x 50 µm i.d.); background electrolyte consisted of a combination of 10 mmol L-1 borate buffer and 5 mmol L-1 anionic detergent sodium dodecyl sulfate (95:5; v/v) pH 6.5; hydrodynamic mode at 50 mBar for 5 s; 25 kV separation voltage at 25 ºC; and column temperature 25 ºC with detection at 257 nm. The proposed method, validated following ICH guidelines, was applied to the determination of this antihypertensive with good results compared with an LC method.

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Bauhinia forficata is used in folk medicine for its hypoglycemiant effect. In the south of Brazil, the subspecies pruinosa is found in a region with the characteristic flora, pampa biome. This species has been consumed by the local population as a tea for diabetes treatment. We studied the chemical composition of hydroethanolic extracts using LC/ESI-MS. The leaf extracts were prepared by percolation with 50% (v/v) ethanol. The chromatographic analyses were performed using a reverse-phase system, gradient elution with acetonitrile:phosphoric acid 0.05%, and ESI-MS in the positive ion mode. The chemical profile of the flavonoids was suggested to involve four quercetin and kaempferol glycosides.

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In spite of different methods reported in the literature to determine olanzapine in biological fluids, all of them used high volumes of plasma. Therefore, the purpose of this paper was to develop an LC-MS/MS method using small plasma volume (0.1 mL) to apply in a preclinical pharmacokinetic investigation. The method was linear over the concentration ranges of 10 - 1000 ng mL-1. Extraction recoveries, stability, and validation parameters were evaluated. Results were within the acceptable limits of international guidelines. A significant decrease in clearance led to a significant 2.26-times increase in AUC0 - 6h of olanzapine-loaded lipid-core nanocapsules compared with free-olanzapine.

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Quetiapine is an atypical antipsychotic used to treat schizophrenia. However, despite great interest for its chronic therapeutic use, quetiapine has some important side effects such as weight gain induction. The development of a quetiapine nanocarrier can potentially target the drug into central nervous system, resulting in a reduction of systemic side effects and improved patient treatment. In the present work, a simple liquid chromatography/ultraviolet detection (LC/UV) analytical method was developed and validated for quantification of total quetiapine content in lipid core nanocapsules as well as for determination of incorporation efficiency. An algorithm proposed by Oliveira et al. (2012) was applied to characterize the distribution of quetiapine in the pseudo-phases of the nanocarrier, leading to a better understanding of the quetiapine nanoparticles produced. The analytical methodology developed was specific, linear in the range of 0.5 to 100 µg mL−1 (r2 > 0,99), and accurate and precise (R.S.D < ±5%). The absolute recovery of quetiapine from the nanoparticles was approximately 98% with an incorporation efficiency of approximately 96%. The results indicated that quetiapine was present in a type III distribution according to the algorithm, and was mainly located in the core of the nanoparticle because of its logD in the formulation pH (6.86 ± 0.4).

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The dehydration kinetic of Yb, Lu and Y 4-chlorobenzylidenepyruvate was studied by using thermogravimetry and the kinetics parameters obtained by Flynn and Wall method suggest that the dehydration step follows a first order mechanism. The activation energies calculated were 103.6, 96.6 and 97.2 kJ/mol and the lifetime considering the temperature of 31 and 101 º C for the dehydration of these compounds were 23, 26, 31 minutes and 0.6, 1.3 and 1.4 seconds, respectively. The results have similar values and suggest that the water is attached in the same way.