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961.
Identification of substances migrating from plastic baby bottles using a combination of low‐resolution and high‐resolution mass spectrometric analysers coupled to gas and liquid chromatography 下载免费PDF全文
Matthias Onghena Els Van Hoeck Joris Van Loco María Ibáñez Laura Cherta Tania Portolés Elena Pitarch Félix Hernandéz Filip Lemière Adrian Covaci 《Journal of mass spectrometry : JMS》2015,50(11):1234-1244
This work presents a strategy for elucidation of unknown migrants from plastic food contact materials (baby bottles) using a combination of analytical techniques in an untargeted approach. First, gas chromatography (GC) coupled to mass spectrometry (MS) in electron ionisation mode was used to identify migrants through spectral library matching. When no acceptable match was obtained, a second analysis by GC‐(electron ionisation) high resolution mass spectrometry time of flight (TOF) was applied to obtain accurate mass fragmentation spectra and isotopic patterns. Databases were then searched to find a possible elemental composition for the unknown compounds. Finally, a GC hybrid quadrupole‐TOF‐MS with an atmospheric pressure chemical ionisation source was used to obtain the molecular ion or the protonated molecule. Accurate mass data also provided additional information on the fragmentation behaviour as two acquisition functions with different collision energies were available (MSE approach). In the low‐energy function, limited fragmentation took place, whereas for the high‐energy function, fragmentation was enhanced. For less volatile unknowns, ultra‐high pressure liquid chromatography‐quadrupole‐TOF‐MS was additionally applied. Using a home‐made database containing common migrating compounds and plastic additives, tentative identification was made for several positive findings based on accurate mass of the (de)protonated molecule, product ion fragments and characteristic isotopic ions. Six illustrative examples are shown to demonstrate the modus operandi and the difficulties encountered during identification. The combination of these techniques was proven to be a powerful tool for the elucidation of unknown migrating compounds from plastic baby bottles. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
962.
Here we describe catalytic asymmetric synthesis of α-(trifluoromethyl)benzylamine (1) via biomimetic transamination using chiral base. Imine 4 was isomerized to Schiff base 5 using 50 mol.% of cinchonidine derivatives as a catalyst in chloroform, methanol or acetonitrile. In the case of cinchonidine 6 as a catalyst, the reaction conducted in chloroform allowed for 79% conversion of the starting imine 4 in 52 days. The product imine 5 was obtained of (R) absolute configuration in 35% ee as individual compound without any byproducts. The catalyst 6 can be recovered (>95%) by adding n-hexane to the reaction mixture followed by a simple filtration. 相似文献
963.
Various studies have been drawn toward the beneficial properties of fruit juices because they have several components, such
as phenols, vitamins, and flavonoids, with antioxidant effects. However, fruit juices can also contain residues of pesticides
used as standard pest control methods in crops. Many of these pesticides are degraded through oxidative mechanisms, and their
persistence in juices can be enhanced by antioxidants. This study covers the degradation of four pesticides, aldicarb, demeton-S-methyl,
fenamiphos, and methiocarb, to their respective sulfoxide and sulfone in grape juices, water (pH 3.5) and water (pH 3.5) with
quercetin (one of the most important flavonoids of grape) added in an attempt to establish whether the presence of antioxidants
can affect the degradation rate of pesticides. For this purpose, a multiresidue method based on solid-phase extraction (SPE)
was developed for the simultaneous determination of these pesticides and their metabolites in commercial juices. The extraction
procedure was carried out in C18 columns. The subsequent elution of pesticides was performed with dichloromethane prior to the determination by liquid chromatography-tandem
mass spectrometry (LC-MS/MS), using two precursor-product ion transitions. Average recoveries for all the pesticides studied
were higher than 80%, with relative standard deviations lower than 15% in the concentration range 0.005–0.05 μg/mL, and the
quantification limits achieved ranged from 0.1 to 4.6 μg/L. The results demonstrated that degradation was slower in fruit
juices and aqueous solutions with quercetin than in water. Several commercial grape juices were also analyzed to establish
the levels of these pesticides. Methiocarb, fenamiphos, and demeton-S-methyl were found at low levels in some samples. 相似文献
964.
Klejdus B Vacek J Benesová L Kopecký J Lapcík O Kubán V 《Analytical and bioanalytical chemistry》2007,389(7-8):2277-2285
A rapid-resolution HPLC/UV-VIS DAD separation method (which takes <1 min) for the determination and identification of genistin,
genistein, daidzein, daidzin, glycitin, glycitein, ononin, formononetin, sissotrin and biochanin A in fmol quantities in submicroliter
sample volumes was optimized. A linear gradient elution (0 min 22% B, 1.0 min 80% B, 1.4 min 100% B, 1.8 min 22% B) using
a mobile phase containing 0.2 % (v/v) acetic acid (solvent A) and methanol (solvent B) was applied on a Zorbax SB C18 column (1.8 μm particle size) at 80 °C. The method was verified using samples of bits of soy and methanolic extracts from
Trifolium pratense, Iresine herbstii and Ononis spinosa plants. Pseudobaptigenin glucoside, irilone, prunetin, texasin, tlatlancuayin and other isoflavones, in addition to aglycones
of isoflavones and their β-glucosides and malonyl and acetyl derivatives, were identified by UV-VIS DAD and electrospray mass
spectrometric (ESI-MS) detection in the extracts.
Figure Rapid resolution HPLC for determination and identification of isoflavones in soy preparations and plant extracts 相似文献
965.
A. G. Pinus 《Algebra and Logic》2005,44(4):264-269
In issues bearing on the structure of universal algebras
, derived structures, such as automorphism groups Aut
, subalgebra lattices Sub
, congruence lattices Con
, etc., play an important part. On the other hand, in studying universal algebras by the means of model theory, of crucial importance is the question asking which elements of the derived structures under examination are expressible by one or other formulas in the elementary language. Problems concerning the interrelationship of algebras and their derived structures are treated for subalgebras of universal algebras.Supported by RFBR grant No. 02-01-00258.__________Translated from Algebra i Logika, Vol. 44, No. 4, pp. 474–482, July–August, 2005. 相似文献
966.
《Journal of separation science》2018,41(14):2993-3002
A method for the determination of 22 phthalate esters in polystyrene food‐contact materials has been established using ultraperformance convergence chromatography with tandem mass spectrometry. In this method, 22 phthalate esters were analyzed in <3.5 min on an ACQUITY Tours 1‐AA column by gradient elution. The mobile phase, the compensation solvent, the flow rate of mobile phase, column temperature, and automatic back pressure regulator pressure were optimized, respectively. There was a good linearity of 20 phthalate esters with a range of 0.05–10 mg/L, diisodecyl phthalate and diisononyl phthalate were 0.25–10 mg/L, and the correlation coefficients of all phthalates were higher than 0.99 and those of 16 phthalates were higher than 0.999. The limits of detection and the limits of quantification of 15 phthalates were 0.02 and 0.05 mg/kg, meanwhile diallyl phthalate, diisobutyl phthalate, dimethyl phthalate, di‐n‐butyl phthalate, and di(2‐ethylhexyl) phthalate were 0.05 and 0.10 mg/kg, and diisodecyl phthalate and diisononyl phthalate were 0.10 and 0.25 mg/kg. The spiked recoveries were in the range of 76.26–107.76%, and the relative standard deviations were in the range of 1.78–12.10%. Results support this method as an efficient alternative to apply for the simultaneous determination of 22 phthalate esters in common polystyrene food‐contact materials. 相似文献
967.
《Journal of separation science》2018,41(16):3294-3301
Molecularly imprinted covalent organic polymers were constructed by an imine‐linking reaction between 1,3,5‐triformylphloroglucinol and 2,6‐diaminopyridine and used for the selective solid‐phase extraction of benzoxazole fluorescent whitening agents from food samples. Binding experiments showed that imprinting sites on molecularly imprinted polymers had higher selectivity for targets compared with those of the corresponding non‐imprinted polymers. Parameters affecting the solid‐phase extraction procedure were examined. Under optimal conditions, actual samples were treated and the eluent was analyzed with high‐performance liquid chromatography with diode‐array detection. The results showed that the established method has a wide linearity, satisfactory detection limits and quantification limits, and acceptable recoveries. Thus, this developed method possesses the practical potential for the selective determination of benzoxazole fluorescent whitening agents in complex food samples. 相似文献
968.
Emilio Bottari Massimiliano Colombi Chiara De Bernardis Vittorio Rampino 《Natural product research》2018,32(13):1590-1599
EU and Italian laws dealing for the presence of antibiotics or, more in general, drags in food established limits for different kinds of food. Suitable rules exist about the medical treatment of cattle in relation to the production of milk and meat. The adoption of a procedure to check the respect of the law limits is necessary. In this paper, the presence of different classes of antibiotics in milk and in homogenised meat is investigated. Generally, HPLC methods are applied for this purpose. In this paper, the application of polarographic analysis is studied and the results are compared with the chromatographic ones. The comparison is relative to all the phases of analysis including the sample preparation. The results show the advantage of the proposed procedure. 相似文献
969.
Wei Li Weiguo Cheng Xia Yang Qian Su Lihui Dong Pan Zhang Yunan Yi Bin Li Suojiang Zhang 《中国化学》2018,36(4):293-298
In this work, 1,8‐diazabicyclo[5.4.0]undec‐7‐ene (DBU), 1,5‐diazabicyclo[4.3.0]‐5‐nonene (DBN), and imidazole (MIM)‐derived bromide ionic liquids (ILs) were synthesized and used to catalyze the cycloaddition reactions of carbon dioxide (CO2) with several kinds of epoxides to form cyclic carbonates. The DBU derived bromide ionic liquid system was found to have the best catalytic activity among all the tested ILs. The influences of reaction conditions (including temperature, pressure and reaction time) on the reaction of CO2 to propylene oxide (PO) were studied to show the best conditions of 120 °C, 1 MPa, 2.5 h catalyzed by 2 mol% DBU‐derived bromide ionic liquid, with the conversion of PO and the selectivity of propylene carbonate (PC) reaching 99% and 99%, respectively. Under the optimum reaction conditions, the ionic liquid system could be reused at least five times without decrease in selectivity and conversion. NMR spectroscopy and DFT calculations were used to reveal the hydrogen‐bond interaction between ionic liquids and reagent, based on which the reaction mechanism was proposed. 相似文献
970.
高效液相色谱法同时测定动物源性食品中5种磺胺及3种四环素族抗生素残留 总被引:7,自引:0,他引:7
建立了动物源性食品中5种常用磺胺(磺胺甲噁唑、磺胺2甲氧嘧啶、磺胺二甲基嘧啶、磺胺-6甲氧嘧啶、磺胺喹噁啉)及3种四环素族(土霉素、金霉素、四环素)抗生素残留的高效液相色谱同时测定方法.样品经提取,固相萃取净化,浓缩后进行HPLC分离,结合保留时间及二极管阵列检测器(PDA)光谱分析信息定性.添加水平为20、50、100μg/kg时5种磺胺及3种四环素族的平均回收率范围为70%~92%,变异系数小于15%.结果表明,该法简单、快速、灵敏,适用于动物源性食品中多磺胺组份及四环素族组份残留的同时测定. 相似文献