Determinação de ácido valpróico em soro por cromatografia líquida de alta eficiência com detector de arranjo de diodos (CLAE-DAD), após derivatização com brometo de fenacila

Valproic acid (VA) is a drug used to control seizures in several epileptic conditions. In VA pharmacotherapy, therapeutic drug monitoring is recommended to obtain adequate seizure control and avoid toxicity. The aim of this study was to validate a method for the determination of valproic acid in serum, employing high performance liquid chromatography with diode array detection (HPLC-DAD), after derivatization with phenacyl bromide. The calibration curve (y=0.0133x-0.0025) presented good linearity with r²=0.9999. Accuracy (101-115%), intra-assay precision (4.53-8.15%) and inter-assay precision (3.15-6.77%) were acceptable. The quantification limit was 2.0 µg/mL. The method presented similar results to enzyme immunoassay.

Cromatografia de afinidade por íons metálicos imobilizados (IMAC) de biomoléculas: aspectos fundamentais e aplicações tecnológicas

Immobilized Metal Ion Affinity Cromatography - IMAC - is a group-specific based adsorption applied to the purification and structure-function studies of proteins and nucleic acids. The adsorption is based on coordination between a metal ion chelated on the surface of a solid matrix and electron donor groups at the surface of the biomolecule. IMAC is a highly selective, low cost, and easily scaled-up technique being used in research and commercial operations. A separation process can be designed for a specific molecule by just selecting an appropriate metal ion, chelating agent, and operational conditions such as pH, ionic strength, and buffer type.

Comparação entre métodos de quantificação em cromatografia gasosa: um experimento para cursos de química

This article describes an experiment designed to teach quantitative determination in gas chromatography (GC) in Organic and Analytical Chemistry practical classes. The experiment consisted of extracting and analyzing eugenol from clove seeds to perform a quantitative approach aimed at comparing results obtained by external and internal calibration procedures. Therefore, this experiment proved to be very effective tool to enhance students awareness on the need to understand different types of calibration in GC and on how to avoid common experimental errors, and to find the best ways to eliminate their interference during the quantitative analysis phase.

Comparação de diferentes abordagens para avaliação da incerteza na cromatografia gasosa do gás natural

The evaluation of uncertainty associated with an analytic result is an essential part of the measurement process. Recently, several approaches to evaluate the uncertainty in measurement have been developed. Here, the gas chromatography assay uncertainty for natural gas is compared by some of these approaches: the guide to the expression of uncertainty in measurement (GUM) approach, top-down approach (reproducibility estimate from an inter-laboratory study), Barwick & Ellison (data from validation), study of variability and fuzzy approach. The comparison shows that GUM, Barwick & Ellison and fuzzy approaches lead to comparable uncertainty evaluations, which does not happen with the top-down approach and study of variability by the absence of data normality.

Determinação de resíduos de pesticidas em plasma bovino por cromatografia gasosa-espectrometria de massas

An analytical method for the isolation based on matrix solid-phase dispersion technique and gas chromatographic determination of pesticides in cattle plasma is presented. It was fortified 0.25 g of plasma with pesticides and blended with 1 g each C18 and Na2SO4. The homogenized matter was transferred to a SPE cartridge, which contained 1 g of activated florisil with 5 mL acetonitrile. The analites were eluted under vaccum with 15 mL acetonitrile, the extract was analyzed by gas chromatography-mass spectrometry. The limit of quantification of the method was 0.04 mg L-1 for chlorphenvinfos and fipronil and 0.02 mg L-1 for cypermethrin..

Avaliação de solventes de extração por ultrassom usando-se cromatografia líquida de alta eficiência para a determinação de hidrocarbonetos policíclicos aromáticos em solos contaminados

A method using ultrasonication extraction for the determination of 17 polycyclic aromatic hydrocarbons (PAHs), selected by the USEPA and NIOSH as "consent decree" priority pollutants, in soil by High Performance Liquid Chromatography (HPLC) was studied. Separation and detection were completed in 20 min with a C18 columm, acetonitrile-water gradient elution and ultraviolet absorption and fluorescence detections. The detection limits, for a 10 µL of solution injection, were less than 9,917 ng/g in UV detection and less than 1,866 ng/g in fluorescence detection. Several organic solvents were tested for extraction of the 17 PAHs from soils. Acetone was the best solvent among the three solvents tested, and the order of the extraction efficiencies was: acetone>methanol>acetonitrile. Ultrasonication using acetone as solvent extraction was used to evaluate the biodegradation of those compounds in contaminated soil during a vermicomposting process.

Óleo essencial de limão no ensino da cromatografia em camada delgada

This paper describes a simple experiment employing the essential oil of limes which can be applied in undergraduate organic chemistry laboratory classes for the teaching of thin layer chromatography (TLC). The experiment consists in submit lime peel oil to TLC separation employing hexane and dichloromethane as the eluents and five different systems for visualization of the chromatogram. In one experiment it is possible to teach the different variables of the TLC technique. This experiment may also be performed following vapor distillation and liquid-liquid extraction technique in experimental classes.

Determinação de etanol e voláteis relacionados em sangue e fluido oral por microextração em fase sólida em headspace associada à cromatografia gasosa com detector de ionização em chama

The aim of this study was to validate a method for the determination of acethaldehyde, methanol, ethanol, acetone and isopropanol employing solid-phase microextraction associated to gas chromatography with flame ionization detection. The operational conditions of SPME were optimized by response surface analysis. The calibration curves for all compounds were linear with r² > 0.9973. Accuracy (89.1-109.0%), intra-assay precision (1.8-8.5%) and inter-assay precision (2.2-8.2%) were acceptable. The quantification limit was 50 µg/mL. The method was applied to the meaurement of ethanol in blood and oral fluid of a group of volunteers. Oral fluid ethanol concentrations were not directly correlated with blood concentrations.

Validação de métodos cromatográficos de análise: um experimento de fácil aplicação utilizando cromatografia líquida de alta eficiência (CLAE) e os princípios da "Química Verde" na determinação de metilxantinas em bebidas

The validation of analytical methods is an important step in quality control. The main objective of this study is to propose an HPLC experiment to verify the parameters of validation of chromatographic methods, based on green chemistry principles, which can be used in experimental courses of chemistry and related areas.

Efeito da acidez e de modificadores orgânicos na determinação de metilxantinas: um experimento de cromatografia liquida de alta eficiência (CLAE) empregando otimização uni e multivariada

In this work a new experiment using HPLC is proposed in order to explore the role of acidity and the organic modifiers in the determination of methylxanthines in tea and coffee. Multivariate and univariate optimizations of the experimental conditions were used.

Otimização e validação intralaboratorial de método para análise de resíduos de cloranfenicol em leite caprino por cromatografia gasosa com detecção por captura de elétrons (CG/DCE)

The presence of chloramphenicol residues in goat milk can cause toxic effects in the population. The present work consists of the optimization and validation of analytical methodology for determination of chloramphenicol residues in goat milk by GC/ECD. The extraction was made with ethyl acetate and the clean-up with SPE-C18. The identification was made by comparison of retention time and GC/MS, and the quantification by external standard. The method was selective, linearity (0.998), precise (5.8-13.4%), exact (69.87-73.71%) and robust. The LOD and LOQ of method were 0.030 and 0.10 μg/kg, respectively. The method was efficiently for analysis of chloramphenicol in goat milk.

Determinação de compostos fenólicos por cromatografia líquida de alta eficiência isocrática durante estacionamento da erva-mate

Different phenolic compound, 5- caffeoylquinic acid (5-CQA), caffeic acid (AC) and rutin (Ru) contents of yerba-mate (Ilex paraguariensis) Brazilian samples of 06 different regions of São Mateus - Paraná, during natural and accelerated industrial storage, were evaluated. For quantification, a reverse phase HPLC isocratic method was developed and validated using methanol:water (35:65 v/v) acidified with 0.5% acetic acid as mobile phase and a photodiode array detector. The six sample global average contents were (34.90 and 36.10 mg g-1) for 5-CQA, (0.18 mg g-1 and 0.23 mg g-1) for AC and (7.12 and 7.18 mg g-1) for Ru, respectively, for the natural and accelerated storage systems. The results showed that the 5-CQA and Ru content are kept constant during the storage while AC content increase only during accelerated storage.

Determinação de corantes marcadores do tipo azo e antraquinona em combustíveis por cromatografia líquida com detecção eletroquímica

An analytical method based on high-performance liquid chromatography with electrochemical detection has been developed and applied to the determination of Solvent blue 14 (SA-14) and Solvent red 24 (SV-24) in fuel samples. The dyes were better separated on C18 column, using a mobile phase composed of acetonitrile and ammonium acetate (90:10, v/v). Detection was carried out at an oxidation potential of +0.85V. The detector response was linear at concentration range of 7.50×10-8 - 1.50×10-6 mol L-1 (r = 0.997) for SA-14 and SV-24, respectively. The method was used to quantify these dyes in fuels samples with satisfactory accuracy and precision.

Desenvolvimento e validação de método analítico por cromatografia líquida de alta eficiência (CLAE) para determinação de associação de ampicilinas em pó liofilizado para injeção

An analytical method has been developed and validated for the determination of an association of ampicillins in a lyophilized powder for injection by HPLC. The advantage of chromatographic method other than the microbiological one is that, it is possible to monitor precisely, out-of-specification results in quality control processes and also during stability studies, in which an association of ampicillins is present. The proposed HPLC method was developed by using forced degraded samples, in order to reach a selective analysis of ampicillins when in the presence of their degradation products. It was possible to detect benzatine and through indirect calculation, to determine the ampicillin sodium in the drug sample. The method showed to be selective, accurate, precise, robust and linear (from 45.92 to 36.04 μg mL-1 of total ampicillin and from 14.53 to 43.28 μg mL-1 of benzatine). The accuracy determined from recovery test, gave results in the range of 99.41% of total ampicillin to 100.31% of benzatine. Hence, it can be concluded that the proposed HPLC method is applicable for ampicillins determination.

Determinação de citrato de sildenafila e de tadalafila por cromatografia líquida de ultraeficiência com detecção por arranjo de diodos (CLUE-DAD)

A simple ultra-performance liquid chromatographic method for the simultaneous determination of sildenafil citrate and tadalafil was developed and validated. Sample preparation was dissolution in methanol, followed by centrifugation and dilution (1:10) with methanol. Analysis was performed in an Acquity® UPLC system with Acquity® BEH C18 column (2.1 x 50 mm, with 1.7 μm particles). The elution was isocratic with phosphate buffer pH 2.3 and acetonitrile (65:35, v/v) at a flow rate of 0.7 mL/min. The method presented adequate specificity, linearity, precision and accuracy and allowed the determination of the drugs in seized forensic samples.