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José Neri G.?Paniz érico Marlon de M.?Flores Ayrton F.?MartinsEmail author 《Mikrochimica acta》2005,152(1-2):89-92
With the aim of avoiding cumbersome sample treatment, we present a device for the introduction of solid soil samples into
AAS-flames for gold determination, as well as the proposition of earth from anthills as a gold occurrence indicator. A previous
ground sample of anthill earth (0.50 mg) was weighed directly into a small recipient of polyethylene which was then connected
to a sampling boronsilicate glass chamber. The sample was carried by an airflow (5 L min−1) to a quartz cell positioned between the burner top and the optical beam. The generated atomic vapor produced a transient
signal which was totally integrated in three seconds. The performance was compared with conventional flame atomic absorption
spectrometry after proper sample digestion. No significant differences were observed between both procedures (mean deviation
±1.90%), and a LOQ of 0.03 μg Au was achieved using the proposed method. The anthill earth was found to be very suitable for
indication of gold occurrence in soils and related materials. 相似文献
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Cadmium determination in biological samples by direct solid sampling flame atomic absorption spectrometry 总被引:1,自引:0,他引:1
rico Marlon de Moraes Flores Jos Neri Gottfried Paniz Ayrton Figueiredo Martins Valderi L. Dressler Edson Irineu Müller Adilson Ben da Costa 《Spectrochimica Acta Part B: Atomic Spectroscopy》2002,57(12):2187-2193
A direct solid sampling flame atomic absorption spectrometric procedure for trace determination of cadmium in biological samples has been developed. Test samples (0.05–2.00 mg) were ground and weighed into small polyethylene vials, which were connected to the device for solid sample introduction into a conventional air/acetylene flame. Test samples were carried as a dry aerosol to a quartz cell, placed between the burner and the optical path, which had a perpendicular entrance and a slit in the upper part. The atomic vapor generated in the flame produced a transient signal that was totally integrated within 1 s. The effect of operating conditions and the extent of grinding on the analytical signal were evaluated. Background signals were always low and a characteristic mass of 0.29 ng Cd was obtained. Calibration was performed using different masses of solid certified reference materials. Results obtained for certified and in-house reference materials were typically within the 95% confidence interval of the certified and/or reference value, and the precision, expressed as relative standard deviation, was between 3.8 and 6.7%. The proposed system is simple and it might be adapted to conventional atomic absorption spectrometers allowing the determination of Cd in more than 80 test samples per hour, excluding weighing. 相似文献
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Diogo P. Moraes Juliana S. F. Pereira Liange O. Diehl Márcia F. Mesko Valderi L. Dressler José Neri G. Paniz Guenter Knapp Érico M. M. Flores 《Analytical and bioanalytical chemistry》2010,397(2):563-570
In this work, three sample preparation methods were evaluated for further halogen determination in elastomers containing high
concentrations of carbon black. Samples of nitrile-butadiene rubber, styrene-butadiene rubber, and ethylene-propylene-diene
monomer elastomers were decomposed using oxygen flask combustion and microwave-induced combustion (MIC) for further Br and
Cl determination by ion chromatography (IC), inductively coupled plasma optical emission spectrometry (ICP OES), and inductively
coupled plasma mass spectrometry (ICP-MS). Extraction assisted by microwave radiation in closed vessels was also evaluated
using water or alkaline solution. Digestion by MIC was carried out using 50 mmol l−1 (NH4)2CO3 as the absorbing solution. The effect of the reflux step was also evaluated. Accuracy was evaluated using certified reference
materials with polymeric matrix composition and by comparison of results using neutron activation analysis. Agreement for
Br and Cl was better than 95% by MIC using 5 min of reflux, and no statistical difference was found using IC, ICP OES, and
ICP-MS for determination of both analytes. For MIC, the relative standard deviation (RSD) was lower than 5%. Using extraction
in closed vessels, a high amount of residues was observed, and recoveries were lower than 45% for both analytes. For oxygen
flask combustion, the agreement was similar using MIC but RSD was higher (20%). The residual carbon content, an important
parameter used to evaluate the digestion efficiency, was always below 1% for MIC. Using MIC, it was possible to digest elastomers
with high efficiency, resulting in a single solution suitable for halogen determination by different techniques. 相似文献
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Paniz Sheikholeslami Christopher M. Ewaschuk Syed Usman Ahmed Benjamin A. Greenlay Todd Hoare 《Colloid and polymer science》2012,290(12):1181-1192
Thermosensitive poly(N-isopropylacrylamide-co-methacrylic acid) (poly(NIPAM-co-MAA)) microgels were prepared via semi-batch free radical copolymerization in which the functional monomer (methacrylic acid) was continuously fed into the reaction vessel at various speeds. Microgels with the same bulk MAA contents (and thus the same overall compositions) but different radial functional group distributions were produced, with batch copolymerizations resulting in core-localized functional groups, fast-feed semi-batch copolymerizations resulting in near-uniform functional group distributions, and slow-feed semi-batch copolymerizations resulting in shell-localized functional groups. Functional group distributions in the microgels were probed using titration analysis, electrophoresis, and transmission electron microscopy. The induced functional group distributions have particularly significant impacts on the pH-induced swelling and cationic drug binding behavior of the microgels; slower monomer feeds result in increased pH-induced swelling but lower drug binding. This work suggests that continuous semi-batch feed regimes can be used to synthesize thermoresponsive microgels with well-defined internal morphologies if an understanding of the relative copolymerization kinetics of each comonomer relative to NIPAM is achieved. 相似文献
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In this study, 1-allyl-3-octylimidazolium tetrachloroferrate ionic liquid was first synthesized. Molecularly imprinted polymer was prepared by suspension polymerization using 1-allyl-3-octylimidazolium tetrachloroferrate as functional monomer and chlorogenic acid as template molecule. The polymer was characterized by Fourier transformed infrared spectroscopy and scanning electron microscopy. Thermal stability of the polymer was investigated. The solid-phase extraction method based on magnetic molecularly imprinted polymer was developed for gallic acid, protocatechuic acid, caffeic acid, chlorogenic acid, p-coumaric acid, and ferulic acid. The sample pH, the type and volume of stripping solution, sorbent amount, and extraction time were optimized for phenolic acids. The analysis of phenolic acids after extraction was carried out using high-performance liquid chromatography with UV detection. Limit of detection, limit of quantification, linear range, correlation coefficient, and reproducibilities of within-day and between-day for phenolic acids were determined. The residues of phenolic acids in apple samples were successfully detected by the developed method. Recovery of standard spiked apple samples was ≥81 for all the phenolic acids. 相似文献
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Shima Majidansari Negin Vahedi Mahmood Rekabgardan Camellia Ganjoury Najmeh Najmoddin Mohammad Tabatabaei Faraz Sigaroodi Paniz Naraghi-Bagherpour Seyed Amir Ali Taheri Mohammad-Mehdi Khani 《先进技术聚合物》2023,34(2):740-747
Cardiovascular diseases have always been one of the main causes of death worldwide and eventually one of the major medical concerns. Tissue engineering is promising strategies of treating cardiovascular, which can be an effective approach with the design of appropriate scaffold. In this study, to develop engineering basement membrane for endothelial differentiation with good cell attachment, we produced polycaprolactone (PCL)/poly (glycerol sebacate) (PGS)/gelatin nanofibrous scaffold via electrospinning. Attenuated total reflectance-Fourier transform infrared and the proton nuclear magnetic resonance results confirmed the chemical structure of synthesized PGS. Scanning electron microscope images of the electrospun scaffold revealed that the nanofibers are smooth, continues and uniform. Moreover, due to the presence of hydrophilic functional groups in the scaffold, the contact angle is in the appropriate range for cell adhesion especially endothelial cells. The elastic modulus and ultimate tensile stress of electrospun scaffold were calculated 1.32 ± 0.27 MPa and 1.23 ± 0.18 MPa respectively. Quantitative polymerase chain reaction was performed for evaluation of endothelial differentiation of mesenchymal stem cells cultured on standard plate and fibrous scaffold under chemical stimulation with growth factor. Specific endothelial gene expression results postulated that our modified scaffold could support and significantly promote endothelial differentiation of MSCs. 相似文献
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