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991.
A selective molecularly imprinted polymer-solid phase extraction for the determination of fenitrothion in tomatoes 总被引:1,自引:0,他引:1
Leonardo Augusto de Barros Isarita Martins Susanne Rath 《Analytical and bioanalytical chemistry》2010,397(3):1355-1361
A new and selective sorbent for molecularly imprinted solid-phase extraction (MISPE) was developed and applied for the determination
of residues of fenitrothion (FNT) in tomatoes, using HPLC coupled to photodiode array detection (HPLC-DAD). Using FNT as the
template molecule, methacrylic acid as the functional monomer, ethylene glycol dimethacrylate as the cross-linker, toluene
as the porogenic solvent, and bulk polymerization as the synthetic method, a molecularly imprinted polymer (MIP) was synthesized.
In order to choose the medium which promotes the best molecular recognition of FNT by the MIP, the adsorption of FNT by the
MIP was studied in different media containing acetonitrile and toluene. Besides FNT, three structurally related compounds
were used to evaluate the selectivity of the FNT-molecularly imprinted polymer. The MIP exhibited the highest selective rebinding
to FNT. The method developed was validated, using fortified blank tomato samples. The extraction efficiency was 96%. The limits
of detection and quantitation were 0.050 and 0.130 μg g−1, respectively. The intra-day precision was 5.9% and the inter-day precision 8.1%. The accuracy was higher than 89% for a
concentration level around the maximum residue limit of 0.5 μg g−1. 相似文献
992.
Characterization of crude oil biomarkers using comprehensive two‐dimensional gas chromatography coupled to tandem mass spectrometry 下载免费PDF全文
Noroska Gabriela Salazar Mogollón Paloma Santana Prata Jadson Zeni dos Reis Eugênio Vaz dos Santos Neto Fabio Augusto 《Journal of separation science》2016,39(17):3384-3391
Oil samples from Recôncavo basin (NE Brazil), previously analyzed by traditional techniques such as gas chromatography coupled to tandem mass spectrometry, were evaluated using comprehensive two‐dimensional gas chromatography coupled to quadrupole mass spectrometry and comprehensive two‐dimensional gas chromatography coupled to tandem mass spectrometry along with simplified methods of samples preparation to evaluate the differences and advantages of these analytical techniques to better understand the development of the organic matter in this basin without altering the normal distribution of the compounds in the samples. As a result, the geochemical parameters calculated by comprehensive two‐dimensional gas chromatography coupled to tandem mass spectrometry described better the origin, maturity, and biodegradation of both samples probably by increased selectivity, resolution, and sensitivity inherent of the multidimensional technique. Additionally, the detection of the compounds such as, the C(14α‐) homo‐26‐nor‐17α‐hopane series, diamoretanes, nor‐spergulanes, C19–C26 A‐nor‐steranes and 4α‐methylsteranes resolved and detected by comprehensive two‐dimensional gas chromatography coupled to tandem mass spectrometry were key to classify and differentiate these lacustrine samples according to their maturity and deposition conditions. 相似文献
993.
Georgia Vieira De Vasconcelos Vilaa Pinto Csar Augusto Moraes De Abreu Augusto Knoechelmann Yêda Medeiros Bastos De Almeida 《Macromolecular Symposia》1999,148(1):333-343
Several techniques have been applied for the characterization of three PET films surfaces: homopolymer PET film, corona treated PET film and a poly(ethylene terephthalate-co-1,4-cyclohexanedimethanol) film. The objective of this work is to investigate and to apply precise and mutually complementary techniques which give detailled information about theses surfaces, as there are few papers with global and conclusive results. The film surfaces were investigated to support the development of new products and envisage new apllications to the existent films. Scanning electron micrographs, attenuated total reflection Fourier transform infrared spectroscopy (FTIR-ATR) and multiple internal reflection Fourier transform infrared spectroscopy (FTIR-MIR) spectra show that the chemical composition, topography and surface roughness of the films are different. The corona-treated PET film shows high surface tension value due to the major contribution on the polar groups and oxidation level acquired. The copolyester film is much less crystalline than the other films analyzed, as demonstrated by refractive index measurements and X-ray photoelectron spectroscopy (XPS). The amorphous structures obtained and the high tension level of the corona-treated films provide a better understanding of the adhesion phenomena. In view of results obtained, one can assume that corona treated films owing to its higher surface tension and films with CHDM owing to its surface amorphization should provide manufacturing industries better processing conditions than films without surface treatment and also higher levels of adhesion to paints and coatings. 相似文献
994.
995.
Maria Isabel Gomes Salema Ana Paula Barbosa-Povoa Augusto Q. Novais 《European Journal of Operational Research》2007
In this work the design of a reverse distribution network is studied. Most of the proposed models on the subject are case based and, for that reason, they lack generality. In this paper we try to overcome this limitation and a generalized model is proposed. It contemplates the design of a generic reverse logistics network where capacity limits, multi-product management and uncertainty on product demands and returns are considered. A mixed integer formulation is developed which is solved using standard B&B techniques. The model is applied to an illustrative case. 相似文献
996.
997.
O Delgado-Vasallo J L Pe?a E San Martín Martínez A Calderón G Pe?a Rodríguez M R Jaime Fonseca E Marín 《Analytical sciences》2003,19(4):599-602
We report here on the use of the photoacoustic technique for the determination of low concentrations of total iron in corn meal samples. The determination of this element in food is of considerable interest because several foods are currently enriched with it at proper levels in order to increase the resistance of people, after consumation, to several diseases, such as anemia. The proposed technique is based on an open photoacoustic cell configuration in conjunction with a suitable colorimetric method. We applied it to a measurement of the total iron concentration in corn meal samples. The results agree very well with those obtained using a conventional spectrophotometric method, showing the possibilities of new experimental methodologies based on photothermal methods to perform this kind of study, with the advantage of a higher sensitivity and increment of the range of appreciable absorbance. 相似文献
998.
The study of lowersemicontinuity properties in W1·p of multiple integrals with quasiconvex integrands withq growth is undertaken forp >q ? 1. In the case where the integrand is not quasiconvex, the absolutely continuous part of the relaxed functional is analyzed. 相似文献
999.
We show that the usual formulation of the N = 4 supersymmetric Yang-Mills theory in terms of N = 1 superfields can be generalized to describe the full ten-dimensional theory. 相似文献
1000.