Evaluation of Dispersive Liquid–Liquid Microextraction–HPLC–UV for Determination of Deoxynivalenol (DON) in Wheat Flour

A fast and simple method for the extraction of deoxynivalenol (DON) from wheat flour using dispersive liquid–liquid microextraction (DLLME) followed by high-performance liquid chromatography–UV detection has been developed and compared with immunoaffinity column cleanup (IAC) process. The influence of several important parameters on the extraction efficacy was studied. Under optimized conditions, a linear calibration curve was obtained in the range of 50–1,000 μg/L. Average recoveries of DON from spiked wheat samples at levels of 500 μg/kg for DLLME and IAC ranged from 72.9?±?1.6 and 85.5?±?3.1, respectively. A good correlation was found for spiked samples between DLLME and IAC methods. The limit of detection was 125 and 50 μg/kg for DLLME and IAC method, respectively. Advantages of DLLME method with respect to the IAC have been pointed out.     

Determination of Pesticide Residues in Whole Wheat Flour Using Modified QuEChERS and LC–MS/MS

Pesticides in food are a major issue due to their intensive use in agriculture. Thus, an appropriate control of their residues in food samples should be done. In this study, a multiresidue method for the quantification of 37 pesticides in whole wheat flour was developed and validated. The modified QuEChERS (without cleanup) procedure followed by ultra-high performance liquid chromatography coupled to tandem mass spectrometry (UHPLC–MS/MS) was used for analysis. The method was validated according to the European Union SANCO/12,571/ 2013 guidelines and Brazilian Manual of Analytical Quality Assurance. The following parameters were evaluated on the method validation: linearity, limit of detention, limit of quantification, matrix effect, precision, accuracy evaluating the percentage of recovery at three different spike levels, and robustness. Acceptable values were obtained. The linear range used was 1–200 μg kg^?1, resulting to r ² of >0.99. The recovery was satisfactory with 70 and 120 % and RSD of <20 % for most compounds. Assessing the samples collected in the south Brazil region, some pesticide residues were detected in whole wheat flour (carbendazim, chlorpyrifos, deltamethrin, imidacloprid, malathion, pendimethalin, pirimiphos-methyl, triamedifom, and triadimenol). The applicability of this analytical approach was confirmed by successful determination of pesticides in whole wheat flour, a complex matrix.

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Determination of Free Amino Acids in Coated Foods by GC–MS: Optimization of the Extraction Procedure by Using Statistical Design

The development and validation of an extraction procedure for quantification of free amino acids in coated products by MTBSTFA derivatization and GC–MS detection is described. The extraction method entailed the sample homogenization with hydrochloric acid (HCl) by stirring at 40 °C followed by two centrifugation steps. The optimum combination of the extraction variables was achieved by response surface methodology. HCl concentration and volume and stirring time influenced free amino acid extraction yield. The selected optimal extraction conditions were 5 g of sample mixed to 7.5 ml of 0.1 N HCl and stirred during 90 min. Consistency between predicted and experimental values as well as in the quality parameters was observed. The calibration curves were linear within the range 5–100 μg ml^?1 with correlation coefficient values (R ² ) higher than 0.99. Detection and quantification limits of the analytical procedure ranged from 2.10^?5 to 18.10^?2 μg μl^?1 and from 8.10^?5 to 60.10^?2 μg μl^?1, respectively. Precision was 0.20–12.59 % for run-to-run and 3.38–17.60 % for day-to-day. The accuracy is between 82.99 and 115.77 %. Nineteen amino acids were analyzed in frozen-thawed and deep-fried coated products from different origin, with cysteine being the most relevant.     

Optimization of Microwave-Assisted Extraction Procedure to Determine Metal in Fish Muscles Using Box–Behnken Design

This study describes the application of response surface methodology (RSM) to develop a method for zinc, lead, manganese, nickel, iron, and copper determination by flame atomic absorption spectrometry in Snow trout (Schizothorax zarudnyi) samples after extraction by a microwave system. The effects of various parameters such as irradiation power, temperature, extraction time, and concentration of nitric acid were investigated by a fractional factorial design (2⁴⁻¹) to determine the significant parameters and their interactions. The results showed that all of the parameters were significant (p < 0.05). The RSM, based on Box–Behnken design, was employed to obtain the optimum conditions of the significant parameters. The optimal conditions could be obtained at a power of 685.0 W, temperature of 116 °C, extraction time of 38.0 min, and 2.5 (mol L⁻¹) for nitric acid concentration. The method was applied for determination of zinc, lead, manganese, nickel, iron, and copper in Snow trout (Schizothorax zarudnyi) samples.     

Discrimination Between the Grain of Spelt and Common Wheat Hybrids and their Parental Forms Using Fourier Transform Infrared–Attenuated Total Reflection

The grain of five spring spelt lines, three common wheat cultivars, and their hybrids were analyzed by Fourier transform infrared–attenuated total reflection spectroscopy. Variations in the log(absorbance) values in the range of 900–1200 cm^?1 (carbohydrates), 1520–1550 cm^?1 (amides II), 1637–1655 cm^?1 (amides I), and 2850–2955 cm^?1 (lipids) indicated that hybrids were more similar to common wheat than to spelt. Significant differences between common wheat and spelt were reported in the above wavenumber range. No such differences were noted between common wheat × spelt and spelt × common wheat hybrid groups. A classical discriminant analysis indicated that hybrids were more similar to common wheat than to spelt. Fourier transform infrared–attenuated total reflection emerges as a highly suitable tool for the identification of spelt grains intended for human consumption or further processing.     

Development of a Dispersive Liquid–Liquid Microextraction Method for the Determination of α-Tocopherol in Pigmented Wheat by High-Performance Liquid Chromatography

A dispersive liquid–liquid microextraction (DLLME) method coupled to high-performance liquid chromatography was developed for the analysis of α-tocopherol in grain samples. The DLLME parameters including the type and volume of extractants, the volume of disperser and the addition of salt were examined. The optimized DLLME procedure consisted in the formation of a cloudy solution promoted by the fast addition to the sample (5 mL of saponified sample solution diluted with 5 mL of water) of a mixture of carbon tetrachloride (extraction solvent, 80 μL) and ethanol (dispersive solvent, 200 μL) without the addition of salt, followed by shaking for 5 min and centrifuging for 3 min at 5,000 rpm. Intra- and inter-day repeatability expressed as % RSD were 3.5 and 7.6 %, respectively. The limit of detection and the limit of quantification were 1.9 and 6.3 μg?L^?1. The comparison of this method with the national standardized extraction method, supercritical carbon dioxide extraction, accelerated solvent extraction, and conventional heat-reflux extraction indicates that the DLLME was accurate (no significant differences at the 0.05 % probability level), high efficient, low organic solvent-consuming, and low cost. This procedure was successfully applied to 42 samples of 14 types of purple wheat, for which the content of α-tocopherol exhibited a significantly negative correlation with the pigment content measured by a spectrophotometer. The recovery rates ranged from 90.5 to 103.7 %.     

Application of Box–Behnken Design in the Optimization of In Situ Surfactant-Based Solid Phase Extraction Method for Spectrophotometric Determination of Quinoline Yellow in Food and Water Samples

In this work, a simple, rapid and sensitive method using in situ surfactant-based solid phase extraction (ISS-SPE) combined with UV–vis spectrophotometry has been developed for the preconcentration and determination of trace amounts of quinoline yellow in food and water samples. The Box–Behnken design was employed to optimize the extraction efficiency. The variables of interest were pH, surfactant volume, extraction time and NaI volume. In the optimal conditions, the calibration graph was linear in the range of 10.0–750 μg L^?1 with a correlation coefficient of 0.9982. The limit of detection (LOD) was 2.1 μg L^?1, and the preconcentration factor was calculated to be 51.8.     

Solid Phase Extraction of Pb(II) and Cd(II) in Food,Soil, and Water Samples Based on 1-(2-Pyridylazo)-2-Naphthol-Functionalized Organic–Inorganic Mesoporous Material with the aid of Experimental Design Methodology

An effective sorbent of 1-(2-Pyridylazo)-2-naphthol-functionalized mesoporous silica has been prepared to simultaneous separation and preconcentration of lead and cadmium ions in aqueous solution. Structural characterization of 1-(2-Pyridylazo)-2-naphthol-functionalized organic–inorganic hybrid mesoporous materials was conducted by Fourier transform infrared spectroscopy, transmission electron microscopy, N₂ adsorption–desorption measurement, X-ray diffraction, and elemental and thermal analysis, which confirmed the successful grafting of organic moiety on mesoporous silica. The affecting parameters on adsorption and desorption steps were optimized by Box-Behnken design through response surface methodology. Three variables (pH value, sorption time, and amount of the sorbent) were selected as the main factors affecting sorption step, while four variables (type of eluent, eluent volume, eluent concentration, and elution time) were selected for desorption step in the optimization study. The optimized values by this optimization method were 10 mg, 8 min, 6.3, HCl, 1.6 mL, 1.2 mol L^?l HCl, and 10 min, for amount of sorbent, sorption time, pH of solution, type, volume, and concentration of the eluent, and elution time, respectively. Under the optimized conditions, the detection limits of the proposed method for lead and cadmium ions were found to be 0.9 and 0.04 μg L^?1, respectively, while the relative standard deviation (RSD) for five replicate measurements was calculated to be <3 % for both ions. For proving that the proposed method is reliable, a wide range of food, soil, and water samples with different and complex matrixes was used.