Um equipamento de eletroforese capilar com detecção condutométrica construído em laboratório

A new construction of a capillary electrophoresis instrument with a universal conductivity detector (oscillometric detector) is described. The performance of the electrophoresis equipment was evaluated through the separation and detection of inorganic anions and cations in aqueous solutions. The results reproduced those found in the literature for the investigated probe ions, showing an efficient separation and good repeatability.

Avaliação de contaminantes inorgânicos e orgânicos em álcool combustível utilizando eletroforese capilar

This work reports the analysis of inorganic and organic contaminants in alcohol fuel samples using capillary electrophoresis. Chloride and sulfate were analyzed in nitrate/ monochloroacetic acid at 10 mmol L-1 concentration each under indirect UV detection (210 nm). The analysis of aldehydes is based on the 216 nm detection of 3-methyl-2-benzothiazoline hydrazone adducts. The running buffer consisted of 20 mmol L-1 tetraborate , 40 mmol L-1 sodium dodecyl sufate and 12 mmol L-1 beta-ciclodextrin. Both methodologies were applied to real samples indicating inorganic ion concentrations from 0.15 to 6.64 mg kg-1 and aldehydes from 32.0 to 91.3 mg L-1.

Metodologias analíticas para determinação das fumonisinas em milho e alimentos à base de milho

Fumonisins are mycotoxins occurring worldwide, mainly in maize and maize-based food products, which could affect animal and human health. This paper reviews analytical methodologies for the determination of these fungal toxins in foods. It includes extraction, cleanup, derivatization procedures, detection, quantification, and confirmation procedures. Initial attempts at gas chromatographic methods and thin layer chromatography were supplanted by liquid chromatographic methods, mainly performed with fluorometric detection, or mass spectrometry detection, enabling the analysis of polar and thermolabile chemicals without chemical derivatization, which results in lower limits of detection. Alternative methods, such as enzyme linked immunosorbent assay or zone capillary zone electrophoresis, are also described.

Fases estacionárias monolíticas para separações cromatográficas

Monolithic stationary phases represent a new generation of chromatographic separation media. These phases consist of a continuous separation bed prepared by in situ polymerization or consolidation inside the column tubing. In recent years, their simple preparation procedure, unique properties and excellent performance have attracted quite remarkable attention in liquid chromatography and capillary electrochromatography. This review summarizes the preparation, characterization and applications of monolithic stationary phases. The analytical potential of these columns is demonstrated with separations involving various families of compounds in different separation modes.

Óleo essencial de Gochnatia polymorpha (Less) Cabr. ssp floccosa Cabr.

The essential oil isolated by hydrodistillation from flowers and root bark of Gochnatia polymorpha (Less) Cabr. ssp floccosa Cabr. (Asteraceae) was analyzed by capillary GC/MS. Thirty components were identified in oil of flowers. The composition depends on the stage of flowering. At the beginning of flowering, the main components were (E)-nerolidol (20,4%) and eugenol (17,9%) whereas at the end they were phenylacetaldehyde (14,6%) and tricosane (12,0%). In the essential oil of root bark ten sesquiterpenes were identified. The major components were beta-bisabolene (31,0%) and beta-bisabolol (21,5%). This paper describes for the first time the composition of essential oil in the genus Gochnatia.

Utilização de um monitor de vídeo como fonte de alta tensão para eletroforese capilar

This article describes the use of a conventional CRT monitor as a high voltage power supply for capillary electrophoresis. With this monitor, a 23-kV high voltage with a ripple of 1.32% was observed. The reproducibility of the applied high voltage was evaluated by measuring the standard deviations of peak area and migration time for five consecutive injections of a test mixture containing potassium, sodium, and lithium cations at 50 mmol L-1. The errors were about 2.5% and 0.6% for peak area and migration time, respectively. The maximum current tested was about 180 mA, which covers most capillary electrophoresis applications. This system has been successfully used for several months, maintaining the desired level of performance.

Cafeína: revisão sobre métodos de análise

Gravimetric and Bailey-Andrew methods are tedious and provide inflated results. Spectrofotometry is adequate for caffeine analysis but is lengthy. Gas chromatography also is applied to the caffeine analysis but derivatization is needed. High performance liquid chromatography with ultraviolet detection (HPLC-UV) and reversed phase is simple and rapid for xanthine multianalysis. In HPLC-UV-gel permeation, organic solvents are not used. HPLC-mass spectrometry provides an unequivocal structural identification of xanthines. Capillary electrophoresis is fast and the solvent consumption is smaller than in HPLC. Chemometric methods offer an effective means for chemical data handling in multivariate analysis. Infrared spectroscopy alone or associated with chemometries could predict the caffeine content in a very accurate form. Electroanalytical methods are considered of low cost and easy application in caffeine analysis.

Terminologia para as técnicas analíticas de eletromigração em capilares

This is a contribution that presents a translation of the work "Terminology for Analytical Capillary Electromigration Techniques" by Riekkola and collaborators (Pure Appl. Chem., Vol. 76, No. 2, 443-451, 2004) from IUPAC© for the Portuguese Language. Additional terms that had not been defined in native Portuguese were included for the benefit of the local community. Additional notes were also included to clarify some important concepts and to highlight the differences between techniques.

Avaliação da composição química de águas do Sistema Guarapiranga: estudo de caso nos anos de 2002 e 2003

The supply of drinking water in the Metropolitan Area of São Paulo City has been a great and serious challenge in the latest years. This work demonstrates the viability of the evaluation of the degree of contamination of the water reservoirs using analytical procedures, which allow the analysis of several compounds at relatively low cost: stripping square wave voltammetry (SSWV) and capillary zone electrophoresis with contactless conductivity detection (CZE-CCD). The results of ionic composition indicated significant contamination of the Guarapiranga water system by human activities on the reservoir banks. In fact, the Guavirutuba and Itupu streams presented high concentrations of phosphate and ammonium ions. This can be directly related to misuse and unruled occupation of the soil and precarious sanitary infrastructure.

Chemical composition and antimicrobial activity of the essential oil from Aeolanthus suaveolens Mart. ex Spreng

The essential oils from leaves (sample A) and flowers (sample B) of Aeolanthus suaveolens Mart. ex Spreng were obtained by hydrodistillation and analyzed by GC, GC-MS, and chiral phase gas chromatography (CPGC). Six compounds have been identified from the essential oils, representing ca 94.3 and 93% of the oils corresponding to samples A and B, respectively. The major constituents of samples A and B essential oils were respectively, linalool (34.2%/34.9%), (-)-massoialactone (25.9%/17.0%) and (E)-beta-farnesene (25.4%/29.1%). The enantiomeric distribution of the monoterpene linalool was established by analysis on heptakis- (6-O-methyl-2,3-di-O-pentyl)-beta-cyclodextrin capillary column. The antimicrobial activity of the essential oil from leaves and isolated compounds was also evaluated.

Volatile constituents of the oils from Povedadaphne Quadriporata (lauraceae) from "Alberto M. Brenes" biological preserve, Costa Rica

The composition of the leaf, bark and wood oils of Povedadaphne quadriporata W. Burger from Costa Rica were analyzed by capillary GC/FID and GC/MS. One hundred and sixty-three compounds were identified. The major components from the leaf oil were a-pinene (21.2%), germacrene D (18.1%), b-pinene (14.8%), a-phellandrene (7.8%), a-copaene (6.6%), b-caryophyllene (6.1%) and d-cadinene (3.5%). From bark oil, the main constituents were a-pinene (27.7%), p-cymene (7.8%), b-pinene (7.4%), camphene (3.6%), a-copaene (3.5%) and limonene (3.3%). From wood oil, 1,10-di-epi-cubenol (8.0%), a-eudesmol (3.4%), cadalene (3.4%) and d-cadinene (3.0%) were the major compounds identified. This paper describes for the first time the composition of essential oils in this unique species and genus.

Eletroforese capilar acoplada à espectrometria de massas (CE-MS): vinte anos de desenvolvimento

CE-MS has been increasingly used for analysis of a vast array of compounds. This article reviews the different electrophoretic modes, interfaces and mass analyzers that are commonly used in the CE-MS coupling, as well as the technique advantages and performance characteristics. A large compilation of CE-MS applications is also presented. Therefore, this review is both a guide for beginners and a collection of key references for people who are familiar to the technique. Furthermore, this is the first CE-MS review published in a Brazilian journal and marks the installation of the first two commercial CE-MS units in Sao Paulo State.

Volatile compounds of Nectandra salicina (lauraceae) from Costa Rica and their cytotoxic activity on cell lines

The chemical composition of the volatiles of Nectandra salicina growing wild in Costa Rica was determined by capillary GC/FID and GC/MS. Thirty-seven and forty-two compounds were identified in the leaf and branch oils respectively corresponding to about 92.6 and 86.2% of the total amount of the oils. The major components of the leaf oil were: atractylone (14.6%), viridiflorene (10.1%), α-pinene (9.4%), β-caryophyllene (7.2%), α-humulene (7.0%), δ-cadinene (6.1%), β-pinene (6.0%) and germacrene D (5.8%). The major components of the branch oil were: atractylone (21.1%), germacrene D (10.7%), viridiflorene (7.9%) and 7-epi-α-selinene (5.0%). When the oils were tested on different cell lines, all the LD50 values were higher than 150 µg/mL, with values very similar for the leaf and branch oils. Low toxicity could be explained by antagonistic effects among the main compounds present in the oils.

Cromatografia gasosa bidimensional abrangente (GC × GC)

This paper presents the fundamental principles, instrumentation and selected applications of comprehensive two-dimensional gas chromatography (GC × GC). In this technique, introduced in 1991, two capillary columns are coupled and proper modulating interfaces continuously collect the eluate from the first column, transferring it to the second column. The result is a geometric increment in the chromatographic resolution, ensuring separation of extremely complex mixtures in time periods shorter or comparable to those of analysis using conventional gas chromatography and with better detectabilities and sensitivities.

Eletrocromatografia capilar: contextualização, estado da arte e perspectivas

Capillary electrochromatography (CEC) is a separation technique in which the mobile phase flow is based on the application of a voltage across a packed capillary, which generates an electroosmotic flow that transports the analytes along the capillary toward the detector. As it combines the separation mechanisms of high-performance liquid chromatography (HPLC) and of capillary electrophoresis (CE), CEC can be considered a hybrid of HPLC and CE. This review presents some fundamental aspects of CEC and is focused on the instrumental advances of the technique, such as column technology, operation modes and detection systems, presenting recent papers on these topics and some applications and perspectives about CEC.