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Gabriel E.F.M.,Federal University of Goais | dos Santos R.A.,Federal University of Goais | Lobo-Junior E.O.,Federal University of Goais | Rezende K.C.A.,Federal University of Goais | And 2 more authors.
Talanta | Year: 2017

Here we report for the first time the use of an electronic micropipette as hydrodynamic (HD) injector for microchip electrophoresis (ME) devices. The micropipette was directly coupled to a PDMS device, which had been fabricated in a simple cross format with two auxiliary channels for sample volume splitting. Sample flow during the injection procedure was controlled in automatic dispenser mode using a volume of 0.6 µL. Channel width and device configuration were optimized and the best results were achieved using a simple cross layout containing two auxiliary channels with 300 µm width for sample splitting. The performance of the HD injector was evaluated using a model mixture of high-mobility cationic species. The results obtained were compared to the data obtained via electrokinetic (EK) injection. Overall, the HD provided better analytical performance in terms of resolution and injection-to-injection repeatability. The relative standard deviation (RSD) values for peak intensities were lower than 5% (n=10) when the micropipette was employed. In comparison with EK injection, the use of the proposed HD injector revealed an unbiased profile for a mixture containing K+ and Li+(300 µmol L−1 each) over various buffer concentrations. For EK injection, the peak areas decreased from 2.92 ± 0.20–0.72 ± 0.14 V s for K+ and from 1.30 ± 0.10–0.38 ± 0.10 V s for Li+ when the running buffer increased from 20 to 50 mmol L−1. For HD injection, the peak areas for K+ and Li+ exhibited average values of 2.48±0.07 and 2.10±0.06 V s, respectively. The limits of detection (LDs) for K+, Na+ and Li+ ranged from 18 to 23 µmol L−1. HD injection through an electronic micropipette allows to automatically dispense a bias-free amount of sample inside microchannels with acceptable repeatability. The proposed approach also exhibited instrumental simplicity, portability and minimal microfabrication requirements. © 2016 Elsevier B.V.


Da Silva J.A.F.,University of Campinas | Da Silva J.A.F.,Instituto Nacional Of Ciencia E Tecnologia Em Bioanalitica Inctbio | Deblire A.,University of Campinas | De Jesus D.P.,University of Campinas | And 3 more authors.
Journal of the Brazilian Chemical Society | Year: 2011

An instrumental setup for electroosmotic flow (EOF) determination in microfluidic devices is described. The system is based on a trinocular microscope and an integrated photodiode OPT101. The radiation was provided by a high-intensity white LED. For the determinations, patent blue V and methylene blue aqueous solutions were used. The setup was applied for EOF monitoring in hybrid toner/glass and PDMS microchips. For the toner/glass device, the EOF mobility was determined to be (5.75 ± 0.01) 10-4 cm 2 V-1 s-1 at pH 7.0. For PDMS devices the measured EOF mobility was (3.2 ± 0.1) 10-4 cm2 V-1 s-1. Reproducible measurements were obtained in all experiments, which produced results with small errors. The proposed method was compared to the conventional current monitoring method. ©2011 Sociedade Brasileira de Química.


Chagas C.L.S.,Federal University of Goais | Costa Duarte L.,Federal University of Goais | Lobo-Junior E.O.,Federal University of Goais | Piccin E.,Federal University of Minas Gerais | And 3 more authors.
Electrophoresis | Year: 2015

This paper describes for the first time the fabrication of pencil drawn electrodes (PDE) on paper platforms for capacitively coupled contactless conductivity detection (C4D) on electrophoresis microchips. PDE-C4D devices were attached on PMMA electrophoresis chips and used for detection of K+ and Na+ in human tear samples. PDE-C4D devices were produced on office paper and chromatographic paper platforms and their performance were thoroughly investigated using a model mixture containing K+, Na+, and Li+. In comparison with chromatographic paper, PDE-C4D fabricated on office paper has exhibited better performance due to its higher electrical conductivity. Furthermore, the detector response was similar to that recorded with electrodes prepared with copper adhesive tape. The fabrication of PDE-C4D on office paper has offered great advantages including extremely low cost (< $ 0.004 per unit), reduced fabrication time (< 5 min), and minimal instrumentation (pencil and paper). The proposed electrodes demonstrated excellent analytical performance with good reproducibility. For an inter-PDE comparison (n = 7), the RSD values for migration time, peak area, and separation efficiency were lower than 2.5, 10.5, and 14%, respectively. The LOD's achieved for K+, Na+, and Li+ were 4.9, 6.8, and 9.0 μM, respectively. The clinical feasibility of the proposed approach was successfully demonstrated with the quantitative analysis of K+ and Na+ in tear samples. The concentration levels found for K+ and Na+ were, respectively, 20.8 ± 0.1 mM and 101.2 ± 0.1 mM for sample #1, and 20.4 ± 0.1 mM and 111.4 ± 0.1 mM for sample #2. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Mogollon N.G.S.,University of Campinas | Mogollon N.G.S.,Instituto Nacional Of Ciencia E Tecnologia Em Bioanalitica Inctbio | Ribeiro F.A.D.L.,University of Campinas | Ribeiro F.A.D.L.,Instituto Nacional Of Ciencia E Tecnologia Em Bioanalitica Inctbio | And 8 more authors.
Analytica Chimica Acta | Year: 2013

In this paper, a method to determine the composition of blends of biodiesel with mineral diesel (BXX) by multivariate curve resolution with Alternating Least Squares (MRC-ALS) combined to comprehensive two-dimensional gas chromatography with Flame Ionization Detection (GC. ×. GC-FID) is presented. Chromatographic profiles of BXX blends produced with biodiesels from different sources were used as input data. An initial evaluation carried out after multiway principal component analysis (MPCA) was used to reveal regions of the chromatograms were the signal was likely to be dependent on the concentration of biodiesel, regardless its vegetable source. After this preliminary step MCR-ALS modeling was carried out only using relevant parts of the chromatograms. The resulting procedure was able to predict accurately the concentration of biodiesel in the BXX samples regardless of its origin. © 2013 Elsevier B.V.


Campos C.D.M.,University of Campinas | Decampos Braga P.A.,University of Campinas | Reyes F.G.R.,University of Campinas | Dasilva J.A.F.,University of Campinas | Dasilva J.A.F.,Instituto Nacional Of Ciencia E Tecnologia Em Bioanalitica Inctbio
Journal of Separation Science | Year: 2015

Focusing on the demand from the food industry for fast and reliable alternative methods to control the quality of food products, we present in this paper a method for amino acid separation and glutamic acid quantification in complex matrices employing capillary electrophoresis with capacitively coupled contactless conductivity detection. We demonstrate by simulation and experimentally the use of organic solvents in sample preparation to prevent peak splitting and increase stacking in capillary electrophoretic separations of amino acids. Additionally, we obtained results for glutamic acid quantification comparable to those obtained via traditional methods used at industrial sites. We tested premium and low-cost samples with large variations in their glutamic acid content, which demonstrated the wide range of applicability of the method presented herein. The results of the proposed capacitively coupled contactless conductivity detection based capillary electrophoresis method agreed with those obtained by an enzymatic detector and ultra high performance liquid chromatography coupled to tandem mass spectrometry, considering a confidence level of 95%. © 2015 Wiley-VCH Verlag GmbH and Co. KGaA, Weinheim.


Hantao L.W.,University of Campinas | Hantao L.W.,Instituto Nacional Of Ciencia E Tecnologia Em Bioanalitica Inctbio | Aleme H.G.,University of Campinas | Aleme H.G.,Instituto Nacional Of Ciencia E Tecnologia Em Bioanalitica Inctbio | And 8 more authors.
Journal of Chromatography A | Year: 2013

In this paper is reported the use of the chromatographic profiles of volatiles to determine disease markers in plants - in this case, leaves of Eucalyptus globulus contaminated by the necrotroph fungus Teratosphaeria nubilosa. The volatile fraction was isolated by headspace solid phase microextraction (HS-SPME) and analyzed by comprehensive two-dimensional gas chromatography-fast quadrupole mass spectrometry (GC. ×. GC-qMS). For the correlation between the metabolic profile described by the chromatograms and the presence of the infection, unfolded-partial least squares discriminant analysis (U-PLS-DA) with orthogonal signal correction (OSC) were employed. The proposed method was checked to be independent of factors such as the age of the harvested plants. The manipulation of the mathematical model obtained also resulted in graphic representations similar to real chromatograms, which allowed the tentative identification of more than 40 compounds potentially useful as disease biomarkers for this plant/pathogen pair. The proposed methodology can be considered as highly reliable, since the diagnosis is based on the whole chromatographic profile rather than in the detection of a single analyte. © 2013 Elsevier B.V..


Hantao L.W.,University of Campinas | Hantao L.W.,Instituto Nacional Of Ciencia E Tecnologia Em Bioanalitica Inctbio | Aleme H.G.,University of Campinas | Aleme H.G.,Instituto Nacional Of Ciencia E Tecnologia Em Bioanalitica Inctbio | And 7 more authors.
Analytica Chimica Acta | Year: 2012

This review describes the major advantages and pitfalls of iterative and non-iterative multivariate curve resolution (MCR) methods combined with gas chromatography (GC) data using literature published since 2000 and highlighting the most important combinations of GC coupled to mass spectrometry (GC-MS) and comprehensive two-dimensional gas chromatography with flame ionization detection (GC. ×. GC-FID) and coupled to mass spectrometry (GC. ×. GC-MS). In addition, a brief summary of some pre-processing strategies will be discussed to correct common issues in GC, such as retention time shifts and baseline/background contributions. Additionally, algorithms such as evolving factor analysis (EFA), heuristic evolving latent projection (HELP), subwindow factor analysis (SFA), multivariate curve resolution-alternating least squares (MCR-ALS), positive matrix factorization (PMF), iterative target transformation factor analysis (ITTFA) and orthogonal projection resolution (OPR) will be described in this paper. Even more, examples of applications to food chemistry, lipidomics and medicinal chemistry, as well as in essential oil research, will be shown. Lastly, a brief illustration of the MCR method hierarchy will also be presented. © 2012 Elsevier B.V..


Rezende K.C.A.,Federal University of Goais | Moreira R.C.,Federal University of Goais | Logrado L.P.L.,Instituto Nacional Of Criminalistica | Talhavini M.,Instituto Nacional Of Criminalistica | And 2 more authors.
Electrophoresis | Year: 2016

This report describes for the first time the use of microchip electrophoresis (ME) devices integrated with capacitively coupled contactless conductivity detection (C4D) to investigate the authenticity of seized whiskey samples, which were probably adulterated by simple dilution with tap water. The proposed microfluidic platform was explored for the monitoring of anionic species (Cl− and F−) in both original and tampered samples. The best separations were achieved within 70 s using a running buffer composed of lactic acid and histidine (pH = 5.9). ME-C4D devices were used to analyze samples from three different brands (five samples each). Based on the presence of inorganic anions like Cl−, F−, SO4 2− and NO2 − in different amounts, the authenticity of seized whiskeys was compared to original samples. According to the reported data, the proposed microfluidic platform can be useful to help regulatory authorities in the investigation and monitoring of authenticity of commercialized whiskey beverages. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim


Miguel G.C.,University of Campinas | Orlando E.A.,University of Campinas | Simionato A.V.C.,University of Campinas | Simionato A.V.C.,Instituto Nacional Of Ciencia E Tecnologia Em Bioanalitica Inctbio
Quimica Nova | Year: 2013

This work focused on the development and validation of an RP-HPLC-UV method for quantification of beta-lactam antibiotics in three pharmaceutical samples. Active principles analyzed were amoxicillin and ampicillin, in 3 veterinary drugs. Mobile phase comprised 5 mmol L-1 phosphoric acid solution at pH 2.00, acetonitrile with gradient elution mode and detection wavelength at 220 nm. The method was validated according to the Brazilian National Health Surveillance regulation, where linear range and linearity, selectivity, precision, accuracy and ruggedness were evaluated. Inter day precision and accuracy for pharmaceutical samples 1, 2 and 3 were: 1.43 and 1.43%; 4.71 and 3.74%; 2.72 and 1.72%, respectively, while regression coefficients for analytical curves exceeded 0.99. The method had acceptable merit figure values, indicating reliable quantification. Analyzed samples had active principle concentrations varying from -12 to +21% compared to manufacturer label claims, rendering the medicine unsafe for administration to animals.

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