Otimização e validação da técnica de extração líquido-líquido com partição em baixa temperatura (ELL-PBT) para piretróides em água e análise por CG

The liquid-liquid extraction with the low temperature partition technique was developed for the analysis of four pyrethroids in water by CG. Using a factorial design the extraction technique was optimised evaluating the effect of the variables ionic strength, contact time and proportion between sample and solvent volumes. The validation parameters sensitivity, precision, accuracy and detection and quantification limits were evaluated. The LOD and LOQ of the method varied from 1.1 to 3.2 µg L-1 and 2.7 to 9.5 µg L-1, respectively.

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 metodologia analítica por cromatografia líquida para doseamento e estudo da estabilidade de pantoprazol sódico

Pantoprazole is a proton pump inhibitor used in the treatment of digestive ulcers, gastro-esophageal reflux disease and in the eradication of Helicobacter pylori. In this work, an analytical method was developed and validated for the quantification of sodium pantoprazole by HPLC. The method was specific, linear, precise and exact. In order to verify the stability of pantoprazole during dissolution assays, pantoprazole solution in phosphate buffer pH 7.4 was kept at room temperature and protected from light for 22 days. Pantoprazole presented less than 5% of degradation in 6 hours and the half live of the degradation was 124 h.

Validação de metodologia analítica para o doseamento simultâneo de mebendazol e tiabendazol por cromatografia líquida de alta eficiência

The aim of this work was to develop and validate an analytical methodology for simultaneous determination of mebendazole and thiabendazole, two benzimidazoles used as anthelmintics. The method was based on high performance liquid chromatography, using a C18 column, a mobile phase composed of KH2PO4 0.05 mol L-1 and methanol 40:60 (v/v) and UV detection at 312 nm. The results showed that the method presented linearity from 60.0 to 140.0 µg mL-1 for mebendazole and from 99.6 to 232.4 g µL-1 for thiabendazole and it was considered selective, accurate, precise and robust according to the specific resolution from ANVISA, the Brazilian regulatory agency.

Metodologia analítica para quantificar o teor de biodiesel na mistura biodiesel: diesel utilizando espectroscopia na região do infravermelho

Considered the best substitute for diesel, biodiesel can be blended with diesel in any ratio, bringing lots of environmental, economic and social advantages. Brazilian law Nº 11097/2005, proposes the introduction of biodiesel in to the Brazilian energy matrix, mixed with diesel at a minimum percentage of 2%. For consumers and sellers to be sure that the commercialized mixture of biodiesel:diesel contains the correct percentage, it is necessary to develop analytical methodologies to quantify the amount of biodiesel added. This work presents a fast, low-cost and simple methodology to determine the biodiesel proportion in mixtures of biodiesel:diesel, based on infrared spectroscopy.

Recomendações para calibração em Química Analítica parte 2: calibração multianalito

This paper is a translation of an IUPAC document by K. Danzer, M. Otto and L. A. Currie (Pure Appl. Chem., 2004, 76(6), 1215-1225). Its goal is to establish a uniform and meaningful standard for terminology (in Portuguese), notation, and formulation concerning multispecies calibration in analytical chemistry. Calibration in analytical chemistry refers to the relation between sample domain and measurement domain (signal domain) expressed by an analytical function x = f s (Q) representing a pattern of chemical species Q and their amounts or concentrations x in a given test sample and a measured function y = f (z) that may be a spectrum, chromatogram, etc. Simultaneous multispecies analyses are carried out mainly by spectroscopic and chromatographic methods in a more or less selective way. For the determination of n species Qi (i=1,2, ..., n), at least n signals must be measured which should be well separated in the ideal case. In analytical practice, the situation can be different.

Microextração em fase líquida (LPME): fundamentos da técnica e aplicações na análise de fármacos em fluidos biológicos

The analysis of drugs and metabolites in biological fluids usually requires extraction procedures to achieve sample clean-up and analyte preconcentration. Commonly, extraction procedures are performed using liquid-liquid extraction or solid-phase extraction. Nevertheless, these extraction techniques are considered to be time-consuming and require a large amount of organic solvents. On this basis, microextraction techniques have been developed. Among them, liquid-phase microextraction has been standing out. This review describes the liquid-phase microextraction technique based on hollow fibers as a novel and promising alternative in sample preparation prior to chromatographic or electrophoretic analysis. The basic concepts related to this technique and its applicability in extraction of drugs are discussed.

Desenvolvimento de metodologia analítica para determinação de colesterol em ração para ruminantes através de planejamento experimental fatorial

A chromatographic method was developed for cholesterol determination in feed for ruminants using response surface methodology. Among the five approaches of sample preparation methods tested, the saponification of the sample without heating presented less interference in the gas chromatography. The method presented a relative standard deviation (RSD) of 4.3%, recoveries between 84 and 87% and detection limit of 0.001 mg of cholesterol per g of feed.

Otimização da análise isotópica de UF6 utilizando-se a técnica de espectrometria de massas por quadrupolo

A procedure for determining of the isotope ratio 235U/238U in UF6 samples was established using a quadrupole mass spectrometer with ionization by electron impact. The following items were optimized in the spectrometer: the parameters in the ion source that provided the most intense peak, with good shape, for the most abundant isotope; the resolution that reduced the non linear effects and the number of analytical cycles that reduced the uncertainty in the results. The measurement process was characterized with respect to the effects of mass discrimination, linearity and memory effect.

Técnica de bombeio e prova para medidas de absorção de estado excitado e de emissão estimulada, em materiais sólidos dopados com íons terras raras

Rare earth ion doped solid state materials are the most important active media of near-infrared and visible lasers and other photonic devices. In these ions, the occurrence of Excited State Absorptions (ESA), from long lived electronic levels, is commonplace. Since ESA can deeply affect the efficiencies of the rare earth emissions, evaluation of these transitions cross sections is of greatest importance in predicting the potential applications of a given material. In this paper a detailed description of the pump-probe technique for ESA measurements is presented, with a review of several examples of applications in Nd3+, Tm3+ and Er3+ doped materials.

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.

Experimento didático sobre cromatografia gasosa: uma abordagem analítica e ambiental

This paper describes an experiment to teach the principles of gas chromatography exploring the boiling points and polarities to explain the elution order of a series of alcohols, benzene and n-propanone, as well as to teach the response factor concept and the internal standard addition method. Retention times and response factors are used for qualitative identification and quantitative analysis of a hypothetical contamination source in a simulated water sample. The internal standard n-propanol is further used for quantification of benzene and n-butanol in the water sample. This experiment has been taught in the instrumental analysis course offered to chemistry and oceanography students.

Desenvolvimento e validação de metodologia analítica por CLAE-IR para determinação de artemisinina em Artemisia annua L

The aim of this work was to develop and validate an analytical methodology for determination of artemisinin used as antimalaric. The method was based on high performace liquid chromatography, using a CN column with mobile phase composed of methanol : H2O 50:50 (V/V). The results showed that the method presented linearity from 50 to 1500 µg/mL. It was considered selective, accurate, precise according to the specific resolution from ANVISA, the Brazilian regulatory agency.

Estudo da resposta termicamente estimulada do compósito LDPE/CB por meio da técnica de corrente de despolarização termicamente estimulada (TSDC)

The thermally stimulated depolarization current (TSDC) in a range of temperature from 84 to 373 K, has been applied to study the depolarization current of polyethylene and polyethylene composites in form of film and filled with commercial or oxidative surface treatment carbon black. The diagrams of TSDC obtained show that the composite in which the carbon black had received oxidative surface treatment reducing on an average depolarization current intensity in a magnitude order if compared to the composite with commercial carbon black. Therefore in the area between α and β transitions the difference is accentuated by reaching a peak 55 times in a temperature of 240 K. The difference in results is explained in terms of molecular interactions neighboring of carbon black particles.

Síntese e estudo de ortossilicatos de zinco luminescentes com aplicação da técnica sol-gel

Usually, the concepts of the Sol-Gel technique are not applied in experimental chemistry courses. This work presents a feasible experiment for chemistry instruction, which involves the synthesis of luminescent materials - Zn2SiO4, with and without Mn2+ as a dopant - by the Sol-Gel technique. The obtained materials were analyzed by scanning electron microscopy, X-Ray diffraction, IR spectroscopy and luminescence measures by UV-vis spectroscopy. The results allow the students to confirm the luminescent properties of the zinc orthosilicate luminophores as well as the structural features expected from literature data.