The main advantage to the proposed method is the possibility to observe the individual amount of the free fatty acids, which would be useful for researchers interested in studying the effect of the free fatty acids profile on oxidative process in food.
Abstract:A review taking into account the literature reports covering 20 years of fatty acid analysis by capillary electrophoresis is presented. This paper describes the evolution of fatty acid analysis using different CE modes such as capillary zone electrophoresis, non-aqueous capillary electrophoresis, micellar electrokinetic capillary chromatography and microemulsion electrokinetic chromatography employing different detection systems, such as ultraviolet-visible, capacitively coupled contactless conductivity, laser-induced fluorescence and mass spectrometry. In summary, the present review signals that CE seems to be an interesting analytical separation technique that is very useful for screening analysis or quantification of the usual fatty acids present in different matrices, offering short analysis times and a simple sample preparation step as inherent advantages in comparison with the classical methodology, making it a separation technique that is very attractive for quality control in industry and government agencies.
We review the literature covering the evolution of amino acid, protein, lipid and carbohydrate analysis in food samples by electromigration techniques over the last 20 years.
The advent of policies that incentivize or require alternative diesel fuels has increased the demand for the development of fast analytical methods aiming for the quality control of these fuels. This study approached an alternative method for the determination of biodiesel acidity employing capillary zone electrophoresis based on free fatty acids screening and quantification. Sample preparation comprised vortex-assisted liquid-liquid extraction of free fatty acids and was a crucial step for analysis. It was studied through a 3 2 full factorial design considering sample mass and the stirring time. Then, solvent suitability was evaluated univariately. The free fatty acid screening was carried out employing a capillary zone electrophoresis method able to separate C16:0, C18:0, C18:1 n-9, C18:2 n-6, and C18:3 n-3, major fatty acids in a variety of vegetable oils used for biodiesel synthesis. In addition to the straightforward sample preparation protocol, the running time of the developed method was only 12 min. Moreover, ultraviolet absorption indirect detection of analytes was approached to avoid analytes derivatization, considering the lack of chromophore groups in saturated fatty acids. Statistical tests did not evidence any significant differences in the biodiesel acidity determination expressed in percentage of free fatty acids when comparing the proposed capillary zone electrophoresis method and the traditional potentiometric titration approach within the 95% confidence interval, which demonstrates the suitability of this alternative method for the biodiesel quality control in routine.
This paper describes the development, evaluation, features and applications of Chromophoreasy, an alternative Excel-based program for recognition and integration of chromatographic and electrophoretic peaks. The proposed recognition is made according to parameters adjustable by the analyst, such as time range, noise smoothing window size and slope/curvature sensitivity. During integration, retention/migration time, area, height, half-height width, plate numbers, asymmetry factor, US Pharmacopeia tailing factor, resolution and statistical moments are determined. A chromatogram/electropherogram is plotted along with the found baselines. The effect of peak shape (heights and symmetries) and baseline slope over accuracy was evaluated and the precision of recognition/integration was investigated under several simulated conditions, with varied signal-to-noise levels, smoothing modes and smoothing window sizes. Data from liquid and gas chromatography, capillary electrophoresis and electrochromatography techniques with refractive index, flame ionization, capacitively coupled contactless conductivity (lab-made) and ultraviolet absorbance detections, respectively, were treated, illustrating the broad applicability of the proposed program for standard and sample analysis. Statistically similar results were obtained, when compared with other commercial software, showing it to be a simple, practical and reliable tool for general use in the separation area.
A rapid method has been proposed for determination of the main conjugated linoleic acid precursors such as linoleic (C18:2 n-6) and linolenic (C18:3 n-3) acids in forages by capillary zone electrophoresis (CZE) with direct UV detection at 200 nm. Among the fatty acids found in forages, C18:2 n-6 and C18:3 n-3 have received particular attention due to their roles as precursors for the synthesis of conjugated linoleic acid, a class of health-enhancing compounds that is predominantly found in dairy products. The electrolyte background consisted of 12.0 mmol/L tetraborate buffer (pH 9.2) added to 12.0 mmol/L Brij 35®, 17% acetonitrile, and 33% methanol. Under the optimized conditions, the baseline separation of C18:2 n-6 and C18:3 n-3 was achieved within 4 min. The CZE-UV method was compared to GC with a flame ionization detector, which is the American Oil Chemists' Society (AOCS 996.06) official method for fatty acid analysis. The methods did not show any evidence of significant differences within 95% confidence interval (P>0.05). The CZE-UV method was successfully applied to the analysis of 80 genotypes of Brachiaria ruzizienses clones submitted to a genetic improvement program in agricultural research.
In this work, we describe the synthesis of a novel 9-aminoacridine derivative that presents surprisingly different colors when exposed to neutral, acidic or basic mediums with potential application as pH indicator in organic solvents. Furthermore, pKa and molar absorptivity values were determined and theoretical studies supported by density functional theory (DFT) calculations were performed to elucidate the different structures of this compound.Keywords: 9-aminoacridine derivative, pH indicator, organic medium Introduction 9-Aminoacridine (9-AA) is a polycyclic heteroaromatic compound with three fused rings that can be used as specific fluorescent.1,2 Its derivatives, which also have fluorescence properties and are typically colored, have a wide range of applications such as biological activity 3 against neurodegenerative diseases and protozoal parasites. 4 The anticancer effect of nitro-9-aminoacridine derivatives is reported in the literature. 5,6 The 9-AA is also described to be a suitable matrix for the matrix assisted laser desorption/ionization (MALDI) and can even be used as indicator of transmembrane pH difference.7-9 A pH indicator highlights changes in the hydrogenionic potential and can be used to determine chemical processes involving acids and bases. More complex methods of quantifying acidity require expensive instrumentation, what makes the usage of pH indicators still important. 10A relevant application of pH indicators concerns the monitoring of biochemical processes through color changes at visible wavelengths representing protonation and deprotonation of species.11 Several dyes have been used as pH indicators by the reversible action of acid and base forms. 12The pKa value is an important physicochemical parameter to predict the ionization state of a substance for the measurements of pH-dependent molecular properties (solubility and lipophilicity, for example) and in applications such as liquid chromatography and capillary electrophoresis for the separation of ionizable compounds. 13,14 There are several methods to determine pKa values, such as potentiometric titration, 15 ultravioletvisible (UV-Vis) absorption spectroscopy, 16 calorimetry, 17 nuclear magnetic resonance (NMR) spectroscopy, 18 and capillary electrophoresis.19 These are useful techniques for the determination of equilibrium constants due to its accuracy and reproducibility.In this work, it was synthesized the compound 2,4,5,7-tetranitro-9-aminoacridine (TNA), introducing four nitro groups in the aromatic rings of 9-AA (Figure 1), and the new derivative presented different colorations when exposed to neutral, acidic or basic mediums. Moreover, we performed a potentiometric titration to determine its pKa values in different mediums and we also confirmed the structures present in each medium through density functional theory (DFT) calculations. ExperimentalMaterials 9-Aminoacridine hydrochloride monohydrate 98% (Aldrich, São Paulo, Brazil), sulfuric acid 98% (Vetec, Rio de Janeiro, Brazil), nitric acid 65% (Cromoline, São Paulo, B...
publicado na web em 18/02/2015 A fast gas chromatography with a flame ionisation detector (GC-FID) method for the simultaneous analysis of methyl palmitate (C16:0), stearate (C18:0), oleate (C18:1), linoleate (C18:2) and linolenate (C18:3) in biodiesel samples was proposed. The analysis was conducted in a customised ionic-liquid stationary-phase capillary, SLB-IL 111, with a length of 14 m, an internal diameter of 0.10 mm, a film thickness of 0.08 µm and operated isothermally at 160 °C using hydrogen as the carrier gas at a rate of 50 cm s -1 in run time about 3 min. Once methyl myristate (C14:0) is present lower than 0.5% m/m in real samples it was used as an internal standard. The method was successful applied to monitoring basic and acidic catalysis transesterification reactions of vegetable oils such as soybean, canola, corn, sunflower and those used in frying process.
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