Determinação de lamivudina, estavudina e nevirapina, em comprimidos, por cromatografia líquida de alta eficiência

A high performance liquid chromatography method was developed to quantify lamivudine, stavudine and nevirapine combined in tablets. The separation was carried out in less than 10 min using a phosphate buffer of pH 3.0 and acetonitrile (75:25, v/v) as mobile phase, a LiChrospher ODS column and UV detection at 266 nm. The method was linear over the range of 15-135 µg/mL (lamivudine), 4-36 µg/mL (stavudine) and 20-180 µg/mL (nevirapine). The accuracy ranged from 98.56 to 102.04% and intra-day and inter-day precision was less than 1% for the three drugs. The method showed robustness, remaining unaffected by deliberate variations in relevant parameters.

Desenvolvimento e validação de metodologia analítica para determinação de itraconazol em produtos farmacêuticos por CLAE

Itraconazole is a synthetic antifungal drug administered orally with a broad spectrum of activity against mycotic infections. The present work consists of the development and validation of analytical methodology for evaluation of itraconazole in pharmaceutical products by high performance liquid chromatography. The separation was made using the reversed-phase column LC-18, acetonitrile/diethylamine 0.05% v/v, 60:40 v/v, pH 8.0 as mobile phase, methanol as solvent and detection and quantification at 254 nm. The results here obtained show that the analytical methodology is accurate, reproducible, robust and linear over the concentration range 8.0-12.0 µg/mL of itraconazole. The method was applied to pharmaceutical capsules containg itraconazole pellets and showed to be efficient, yielding good results.

Validação de método por cromatografia líquida de alta eficiência para determinação da lamivudina e zidovudina em comprimidos

An HPLC method was validated to assay lamivudine and zidovudine combined in tablets. The chromatographic separation was carried out using methanol and acetate buffer pH 6.5 (50:50 v/v) and a RP-18 column, as mobile and stationary phase, respectively. The UV detection was at 270 nm. The method was linear in the range of 24 - 36 µg/mL (lamivudine) and 48 - 72 µg/mL (zidovudine). The recovery (accuracy) ranged from 101.35% to 103.04% and the precision (repeatability and intermediate precision) was less than 2%. The method can be also applied to the quantification of these drugs in the dissolution test of tablets containing both drugs.

Simultaneous spectrophotometric determination of ezetimibe and simvastatin in pharmaceutical preparations using chemometric techniques

Two spectrophotometric methods are described for the simultaneous determination of ezetimibe (EZE) and simvastatin (SIM) in pharmaceutical preparations. The obtained data was evaluated by using two different chemometric techniques, Principal Component Regression (PCR) and Partial Least-Squares (PLS-1). In these techniques, the concentration data matrix was prepared by using the mixtures containing these drugs in methanol. The absorbance data matrix corresponding to the concentration data matrix was obtained by the measurements of absorbances in the range of 240 - 300 nm in the intervals with Δλ = 1 nm at 61 wavelengths in their zero order spectra, then, calibration or regression was obtained by using the absorbance data matrix and concentration data matrix for the prediction of the unknown concentrations of EZE and SIM in their mixture. The procedure did not require any separation step. The linear range was found to be 5 - 20 µg mL-1 for EZE and SIM in both methods. The accuracy and precision of the methods were assessed. These methods were successfully applied to a pharmaceutical preparation, tablet; and the results were compared with each other.

Validação de métodos para determinação de fluoxetina em cápsulas

A UV spectrophotometric method was developed and validated and a chromatographic method was adapted from the American Pharmacopeia for the analysis of Fluoxetine Hydrochloride capsules. Ethanol was used as solvent for the spectrophotometric method, with detection and determination at 276 nm. The separation for the chromatographic method was carried out using the reversed-phase column LC-8, triethylamine buffer, stabilizer free tetrahydrofuran and methanol (5:3.5:1.5), pH 6.0 as mobile phase and detection at 227 nm. The results obtained for both methods showed to be accurate, precise, robust and linear over the concentration range 100.00 - 300.00 µg/mL and 40.00 - 80.00 µg/mL of fluoxetine hydrochloride for the spectrophotometric and chromatographic methods, respectively. The accuracy of the methods was evaluated by a recovery test and showed results between 98.89 and 101.10%.

Desenvolvimento e validação de método por cromatografia líquida de alta eficiência para determinação simultânea das impurezas timina e timidina na matéria-prima estavudina

A HPLC method was developed to quantify thymine and thymidine impurities in stavudine bulk drug. The separation was carried out in isocratic mode using methanol/water (20:80) as mobile phase, a C18 column and UV detection at 266 nm. The method provided selectivity based on peak purities and resolution among peaks. It was linear over the range of 0.5-5.0 µg/mL. The quantitation limits were 0.021 µg/mL for thymine and 0.134 µg/mL for thymidine. The average accuracies of three concentrations ranged from 97.06 to 102.61% and precision was close to 1%. The method showed robustness, remaining unaffected by deliberate variations in relevant parameters.

Validação de metodologia analítica por cromatografia líquida de alta eficiência para quantificação de bupivacaína (S75-R25) em nanoesferas de poli(lactídeo-co-glicolídeo)

Bupivacaine (S75-R25, NovaBupi®) is an amide type local anesthetic widely used. The present work consists of the development and validation of analytical methodology for evaluation of NovaBupi® content in the poly-lactide-co-glycolide nanospheres (PLGA-NS) by high performance liquid chromatography. The separation was made using the reversed-phase column LC-18, acetonitrile/phosphate buffer 85:15 v/v as mobile phase and detection at 220 nm. The results obtained show that the analytical methodology is accurate, reproducible, robust and linear over the concentration range 10-220.0 g/mL of NovaBupi®. The method was applied to determine the encapsulation efficiency and evaluate the release profile of NovaBupi®, showing good results.

On-line preconcentration system using a microcolumn packed with Alizarin Red S-modified alumina for zinc determination by flame atomic absorption spectrometry

A simple and sensitive on-line flow injection system for determination of zinc with FAAS has been described. The method is based on the separation and preconcentration of zinc on a microcolumn of immobilized Alizarin Red S on alumina. The adsorbed analyte is then eluted with 250 µL of nitric acid (1 mol L-1) and is transported to flame atomic absorption spectrometer for quantification. The effect of pH, sample and eluent flow rates and presence of various cations and anions on the retention of zinc was investigated. The sorption of zinc was quantitative in the pH range of 5.5-8.5. For a sample volume of 25 mL an enrichment factor of 144 and a detection limit (3S) of 0.2 µg L-1 was obtained. The precision (RSD, n=7) was 3.0% at the 20 µg L-1 level. The developed system was successfully applied to the determination of zinc in water samples, hair, urine and saliva.

Aromaticidade: evolução histórica do conceito e critérios quantitativos

In this paper the evolution of the concept of aromaticity is discussed. It considers not only historical aspects of the aromaticity concept but also the different criteria (theoretical and experimental) that have appeared to explain the properties of the aromatic compounds. The topics range from the isolation of benzene by Faraday (1825) until the modern criteria based on geometries, magnetic properties, resonance energy (RE), aromatic stabilization energy (ASE), topological analyses, and others. A chronological separation of issues concerning aromaticity was made, splitting the definitions before and after the appearance of the quantum chemistry. This work reviews the concept of aromaticity.

Simultaneous determination of gemifloxacin and diuretics in bulk, pharmaceutical dosage forms and human serum by RP-HPLC

An isocratic reversed phase high-performance liquid chromatographic (RP-HPLC) method has been developed for the simultaneous determination of gemifloxacin and diuretics (hydrochlorothiazide and furosemide) in bulk, dosage formulations and human serum at 232 nm. Chromatographic separation was achieved on Purospher Start C18 (250 mm x 4.6 mm, 5 µm) column using mobile phase, methanol: water: acetonitrile (70:25:5 v/v/v) adjusted to pH 3.0 via phosphoric acid 85% having flow rate of 0.8 mL min -1 at room temperature. Calibration curves were linear over range of 0.5-10 µg mL -1 with a correlation coefficient ± 0.999. LOD and LOQ were in the ranges of 0.75-2.56 µg mL -1. Intra and inter-run precision and accuracy results were 98.26 to 100.9.

Development and validation of a high performance liquid chromatographic method for determination of cyclosporine-A from biodegradable intraocular implants

An HPLC method was developed and validated aiming to quantify the cyclosporine-A incorporated into intraocular implants, released from them; and in direct contact with the degradation products of PLGA. The separation was carried out in isocratic mode using acetonitrile/water (70:30) as mobile phase, a C18 column at 80 ºC and UV detection at 210 nm. The method provided selectivity based on resolution among peaks. It was linear over the range of 2.5-40.0 µg/mL. The quantitation and detection limits were 0.8 and 1.2 µg/mL, respectively. The recovery was 101.8% and intra-day and inter-day precision was close to 2%.

Preparative separation and purification of sesquiterpenoids from tussilago farfara l. by high-speed counter-current chromatography

Preparative high-speed counter-current chromatography (HSCCC) was successfully applied for separation and purification of sesquiterpenoids from an extract of Tussilago farfara L. with a two-phase solvent system composed of n-hexane-ethyl acetate- methanol-water (1:0.5:1.1:0.3, v/v/v/v). The separation produced a total of 32 mg of tussilagone, 18 mg of 14-acetoxy-7β-(3'-ethyl cis-crotonoyloxy)-lα-(2'-methyl butyryloxy)-notonipetranone and 21 mg of 7β-(3'-ethyl cis-crotonoyloxy)-lα-(2'- methyl butyryloxy)-3,14-dehydro-Z-notonipetranone from 500 mg of the crude extract in one step separation with the purity of 99.5, 99.4 and 99.1%, respectively, as determined by HPLC. The structures of these compounds were identified by ESI-MS, ¹H-NMR and 13C-NMR.

A sensitive and robust lc-ms/ms method with monolithic column and electrospray ionization for the quantitation of efavirenz in human plasma: application to a bioequivalence study

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.

Desenvolvimento e validação de método analítico para determinação de benzoato, sorbato, metil e propilparabenos em produtos alimentícios utilizando a eletroforese capilar

In this work, a rapid and simple method using capillary electrophoresis (CE) was developed for the determination of the benzoate, sorbate, methyl and propylparaben in foodstuffs. A running buffer consisting of 20 mmol L-1 (pH = 9.3) tetraborate enabled separation of the analytes in less than 5 min. The detector wavelength was set at 220 nm. The method was successfully applied to the analysis of sodas, sweeteners, sauces and juices. The range of preservatives found were from 478.5-466.6 mg kg-1 for methylparaben , 83.7-231.3 mg kg-1 for sorbate and 336.7-428.3 mg kg-1 for benzoate.

Dispersive liquid-liquid microextraction for the simultaneous separation of trace amounts of zinc and cadmium ions in water samples prior to flame atomic absorption spectrometry determination

In the proposed method, carbon tetrachloride and ethanol were used as extraction and dispersive solvents. Several factors that may be affected on the extraction process, such as extraction solvent, disperser solvent, the volume of extraction and disperser solvent, pH of the aqueous solution and extraction time were optimized. Under the optimal conditions, linearity was maintained between 1.0 ng mL-1 to 1.5 mg mL-1 for zinc and 1.0 ng mL-1 to 0.4 mg mL-1 for cadmium. The proposed method has been applied for determination of trace amount of zinc and cadmium in standard and water samples with satisfactory results.