Determinação turbidimétrica de metilbrometo de homatropina em formulações farmacêuticas empregando um sistema de análise por injeção em fluxo

A flow injection turbidimetric procedure exploiting merging zones is proposed for determining homatropine methylbromide (HMB) in pharmaceutical preparations. The determination is based on the precipitation reaction of homatropine methylbromide with AgNO3 solution to form a precipitate, which was measured at 410 nm. The analytical curve was linear in the HMB concentration range from 8.0x10-4 to 1.7x10-3 mol L-1, with a detection limit of 9.5x10-5 mol L-1. The recoveries ranged from 94.9 to 104 %, the sampling frequency was 75 h-1 and relative standard deviations were smaller than 2.0 % for solutions containing 1.2x10-3 and 1.5x10-3 mol L-1 HMB (n=10). The results obtained for commercial formulations using the FIA procedure were in good agreement with those obtained by using a comparative method (r= 0.9983).

Desenvolvimento e validação de um método analítico para a determinação de histamina em vinhos utilizando cromatografia líquida de alta eficiência com detecção por fluorescência

A rapid and efficient method for the analysis of histamine in wines using HPLC with fluorescence detection after derivatization was developed and validated. The method LOD and LOQ values were 0.25 and 0.50 mg L-1 respectively. The repeatability and intermediary precision for the instrument and for the method presented RSD values of 3.7 and 2.9%, and 6.0 and 5.6%, respectively. The recoveries were 95.5 and 89.9% for the fortification levels of 2 and 10 mg L-1. The method was applied to determine the histamine content in Cabernet Sauvignon wines, which presented values between 1.2 and 5.7 mg L-1.

Determinação espectrofotométrica simultânea de paracetamol e ibuprofeno em formulações farmacêuticas usando calibração multivariada

A simple method was proposed for determination of paracetamol and ibuprofen in tablets, based on UV measurements and partial least squares. The procedure was performed at pH 10.5, in the concentration ranges 3.00-15.00 µg ml-1 (paracetamol) and 2.40-12.00 µg ml-1 (ibuprofen). The model was able to predict paracetamol and ibuprofen in synthetic mixtures with root mean squares errors of prediction of 0.12 and 0.17 µg ml-1, respectively. Figures of merit (sensitivity, limit of detection and precision) were also estimated. The results achieved for the determination of these drugs in pharmaceutical formulations were in agreement with label claims and verified by HPLC.

Validação em laboratório de método analítico para determinação do teor de adipato e ftalato de di-(2-etil-hexila) utilizados como plastificantes em filmes flexíveis de PVC

The validation of analytical methods was carried out for di-(ethylhexyl) phthalate (DEHP) and adipate (DEHA) the determination of in PVC films. The level of DEHP and DEHA in samples was determined by leaving the film in contact with n-heptane during 48 hours and analysis in a gas chromatograph (GC) equipped with a flame ionization detector and fused silica column with 5% phenylmethyl silicone in the dimensions 30 m x 0.53 mm x 2.65 mm. The results for detection and the quantification limits were smaller than the restriction limits. The recovery rates of DEHP and DEHA were, respectively, 69.10 and 75.30 %.

Determinação da concentração de paclobutrazol por cromatografia líquida de alta eficiência e espectroscopia

Paclobutrazol is a plant growth retardant which is used world-wide for increasing the yield of cereal crops. However, this compound remains active in the soil for several years and can severely affect the growth and development of subsequent crops, mainly by reducing vegetative vigor. The aim of this work was to develop and validate methods for the determination of paclobutrazol concentrations by both high performance liquid chromatography and spectroscopy. Both methods were satisfactory and showed appropriately low quantification limits. The determination by spectroscopy has, however, the advantage of being a method significantly less expensive than high performance liquid chromatography.

Pré-concentração de cádmio com Saccharomyces cerevisiae e determinação em águas fluviais usando espectrometria de emissão óptica com plasma indutivamente acoplado

A preconcentration method based on the use of Saccharomyces cerevisiae as sorbent material is proposed for the determination of Cd(II) in river water. The solid phase extraction was performed in batch mode and the determination of the analyte in the solid phase was easily carried out by introducing a slurry of the yeast (0.0625 g / 2.5 mL) directly into the ICP OES. A limit of detection of 0.11 µg L-1 and a sample throughput in the range of 4 - 54 sample h-1 were obtained. Determinations of cadmium in a certified sample and in real river water samples were in excellent agreement with the expected values.

Determinação de açúcar total em café cru por espectroscopia no infravermelho próximo e regressão por mínimos quadrados parciais

In this work a fast method for the determination of the total sugar levels in samples of raw coffee was developed using the near infrared spectroscopy technique and multivariate regression. The sugar levels were initially obtained using gravimety as the reference method. Later on, the regression models were built from the near infrared spectra of the coffee samples. The original spectra were pre-treated according to the Kubelka-Munk transformation and multiplicative signal correction. The proposed analytical method made possible the direct determination of the total sugar levels in the samples with an error lower by 8% with respect to the conventional methodology.

Utilização da múltipla voltametria de onda quadrada na determinação eletroanalítica de compostos orgânicos e inorgânicos

This paper reports the development of multiple square wave voltammetry and the possibilities of its use for electroanalytical determinations of organic and inorganic compounds with the improvement of the signal-to-noise ratios and detection limits 2-3 orders of magnitude lower than those obtained with conventional square wave voltammetry. The theoretical aspects and analytical applications were demonstrated as an increased analytical response (current) and application of different pulse modes for different redox processes. Preliminary results obtained for several redox systems using different electrode surfaces are shown, demonstrating also that MSWV represents an excellent alternative for the determination of ultra-traces of organic and inorganic compounds.

Determinação do perfil de compostos voláteis e avaliação do sabor e aroma de bebidas produzidas a partir da erva-mate (Ilex paraguariensis)

Volatile compounds from green and roasted yerba mate were analyzed by gas chromatography/mass spectrometry and the flavor profile from yerba mate beverages was determined by descriptive quantitative analyses. The main compounds tentatively identified in green mate were linalool, alpha-terpineol and trans-linalool oxide and in roasted mate were (E,Z)-2,4-heptadienal isomers and 5-methylfurfural. Green mate infusion was qualified as having bitter taste and aroma as well as green grass aroma while roasted mate was defined as having a smooth, slightly burnt aroma. The relationship between the tentatively identified compounds and flavor must be determined by olfatometric analysis.

Utilização da extração em fase sólida (SPE) na determinação de hidrocarbonetos policíclicos aromáticos em matrizes aquosas ambientais

Polycyclic aromatic hydrocarbons (PAHs) are a great environmental concern mainly because of their toxic, mutagenic and carcinogenic potential. This paper reports utilization of the solid-phase extraction (SPE) technique to determine PAHs in environmental aqueous matrices. The recovery from environmental aqueous matrices fortified with PAHs varied from 63.7 to 93.1% for atmospheric liquid precipitation, from 38.3 to 95.1% for superficial river water, and from 71.0 to 95.5% for marine water. No negative matrix effect was observed for the recovery of PAHs from atmospheric liquid precipitation and marine water, but was observed for superficial river water, particularly for PAHs possessing 5 and 6 aromatic rings.

Determinação de zinco em solo utilizando colorimetria

In terms of soil fertility, zinc is a micronutrient that is very important in the culture of soy, maize, rice and coffee, because it is a structural and functional component of a great number of enzymes. Therefore, diverse methods have been used to determine zinc in soil. In this work we use colorimetry as a methods of zinc determination in soil using two methodologies of sample digesting, H2SO4/H2O2 and HNO3/H2O2. In order to compare the results, atomic absorption spectrometry (AAS) was used. Results show that colorimetric methods can be used due to good sensitivity and reproducibility, since the zinc calibration curve showed good linearity. Comparing colorimetric methods with AAS we observed that the results were equivalent, as proven by the statistical values of the F and t of Student tests. Furthermore, both methods of soil digesting can be used, leading to a flexible methodology of low-cost for routine zinc analyses in soil.

Determinação de ascarel em óleo isolante de transformadores

The contamination level of silicon oil used as insulation liquid in high-voltage transformers by ascarel (PCBs) is above those permitted by the Brazilian law. Thus new techniques able to detect ascarel, with low operational costs, are very attractive. The present work proposes an analysis of the contamination levels of silicon oil using the following techniques: naphthalene anion radical reaction for ascarel dechlorination; and potentiometry with an ion-selective electrode for chloride ion determination. The data obtained with the proposed methodology agree well with those from the official methodology, (method IEC 61619).

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.

Avaliação das variáveis analíticas do método de Folin-Ciocalteu para determinação do teor de taninos totais utilizando como modelo o extrato aquoso de folhas de psidium guajava L.

The main analytical variables of a modified Folin-Ciocalteu method were studied by UV-Vis and gradient HPLC-PDA methods, using purified (PC) and technical grade (TGC) casein. Rutin and an aqueous extract of Psidium guajava L. leaves were used as models. The best results were ascribed to TGC. Certainly PC bonds the polyphenols of the P. guajava extract better than TGC, but TGC afforded better precision. A lack of specificity occurred when rutin was analyzed together with the P guajava extract. Additional analyses performed with the flavonoid fraction of P. guajava extract by HPLC-PDA had confirmed that casein was able to bind catechin, gallic acid and P. guajava flavonoids in a non-specific way.

Determinação da composição isotópica de estrôncio em águas naturais: exemplos de sua aplicação em águas subsuperficiais da zona costeira na região Bragantina-PA

Analytical procedures used for determining the concentrations and isotope composition of strontium in subsurface waters, by mass spectrometry, are described. Sampling was performed in coastal plateaus, salt marsh and mangrove environments in the coastal region of Pará. Coastal plateau waters have delta87Sr between 1.51 and 6.26‰ and Sr concentration bellow 58 ppb. Salt marsh waters show delta87Sr between 0.55 and 0.90‰ and Sr concentration between 93 and 114 ppm, while mangrove waters have delta87Sr‰ around zero and Sr concentration above 15 ppm. Differences in the 87Sr/86Sr ratio in these subsurface waters are detected, as well as seasonal variations in the coastal pleteau waters.