Simultaneous determination of 22 phthalate esters in polystyrene food‐contact materials by ultra‐performance convergence chromatography with tandem mass spectrometry

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.     

Dispersive magnetic solid‐phase extraction of phthalate esters from water samples and human plasma based on a nanosorbent composed of MIL‐101(Cr) metal–organic framework and magnetite nanoparticles before their determination by GC–MS

In this study, a magnetic metal–organic framework was synthesized simply and utilized in the dispersive magnetic solid‐phase extraction of five phthalate esters followed by their determination by gas chromatography with mass spectrometry. First, MIL‐101(Cr) was prepared hydrothermally in water medium without using highly corrosive hydrofluoric acid, utilizing an autoclave oven heat supply. Afterward, Fe₃O₄ nanoparticles were decorated into the matrix of MIL‐101(Cr) to fabricate magnetic MIL‐101 nanocomposite. The nanocomposite was characterized by various techniques. The parameters affecting dispersive magnetic solid‐phase extraction efficiency were optimized and obtained as: a sorbent amount of 15 mg; a sorption time of 20 min; an elution time of 5 min; NaCl concentration, 10% w/v; type and volume of the eluent 1 mL n‐hexane/acetone (1:1 v/v). Under the optimum conditions detection limits and linear dynamic ranges were achieved in the range of 0.08–0.15 and 0.5–200 μg/L, respectively. The intra‐ and interday RSD% values were obtained in the range of 2.5–9.5 and 4.6–10.4, respectively. Ultimately, the applicability of the method was successfully confirmed by the extraction and determination of the model analytes in water samples, and human plasma in the range of microgram per liter and satisfactory results were obtained.     

同时加速溶剂萃取/气相色谱-质谱法测定植物中13种有机磷酸酯

建立了同时加速溶剂萃取和净化、气相色谱-离子阱二级质谱检测植物中13种有机磷酸酯阻燃剂/增塑剂的分析方法。样品放入以硅胶和活性炭作为在线净化填料的萃取池中,在萃取溶剂为正己烷-丙酮(1∶1,体积比)、萃取温度100℃、静态萃取时间10 min、循环2次的条件下进行加速溶剂萃取,萃取液浓缩后经DB-5MS(30 m×0.25 mm×0.25μm)气相色谱柱分离,选择反应监测模式(SRM)检测,以保留时间和特征离子对定性,内标法定量。结果表明,该方法具有较好的准确度和精密度,13种有机磷酸酯在3个加标水平下的回收率为76.9%~113.0%,相对标准偏差为2.0%~14.6%,方法检出限为0.79~2.27 ng/g,方法定量下限为2.65~7.59 ng/g。该方法简便、快速、准确,可用于植物中13种有机磷酸酯的测定。     

基于二乙醇胺配体的[Dy2Co8]型配合物的合成、晶体结构和磁性分析

以二乙醇胺为配体合成了一种具有[Dy_2Co_8]核结构的配合物[Dy_2Co_8(L)_4(HL)_4(HCOO)_4(OH)_2Cl_2(CH_3OH)_2]Cl_2·4CH_3OH·2H_2O(1)(H_2L=二乙醇胺),并对其进行了X射线单晶衍射、红外光谱、元素分析和磁性表征。该配合物属于三斜晶系,P1空间群。晶体学数据:a=1.160 4(8)nm,b=1.322 7(9)nm,c=1.465 3(9)nm,α=71.181(7)°,β=67.638(7)°,γ=65.939(7)°。在晶体结构中,每一个Dy(Ⅲ)都是九配位,而每一个Co(Ⅱ)均为六配位。     

Chemoselectivity Control in the Asymmetric Hydrogenation of γ‐ and δ‐Keto Esters into Hydroxy Esters or Diols

The asymmetric hydrogenation of aromatic γ‐ and δ‐keto esters into optically active hydroxy esters or diols under the catalysis of a novel DIPSkewphos/3‐AMIQ–Ru^II complex was studied. Under the optimized conditions (8 atm H₂ , Ru complex/t‐C₄H₉OK=1:3.5, 25 °C) the γ‐ and δ‐hydroxy esters (including γ‐lactones) were obtained quantitatively with 97–99 % ee. When the reaction was conducted under somewhat harsh conditions (20 atm H₂ , [t‐C₄H₉OK]=50 mm , 40 °C), the 1,4‐ and 1,5‐diols were obtained predominantly with 95–99 % ee. The reactivity of the ester group was notably dependent on the length of the carbon spacer between the two carbonyl moieties of the substrate. The reaction of β‐ and ?‐keto esters selectively afforded the hydroxy esters regardless of the reaction conditions. This catalyst system was applied to the enantioselective and regioselective (for one of the two ester groups) hydrogenation of a γ‐?‐diketo diester into a trihydroxy ester.     

Direct Transformation of Esters into Heterocyclic Fluorophores

Despite the manifold use of heterocyclic fluorophores, only a fraction of the desired dye diversity can be accessed by contemporary synthetic approaches. Herein, we describe a modular method that converts various carboxylic acid esters directly into a broad spectrum of heteroanthrylium fluorophores. The double addition of heteroatom‐bridged 1,5‐bifunctional organomagnesium reagents to esters leads to the formation of acridinium, xanthylium, and SiR fluorophores after dehydrative acidic work‐up. This one‐step synthetic method provides access to organophotoredox catalysts for dual catalysis with nickel and dyes amenable to fluorescence enhancement.     

Optimization of 2-alkoxyacetates as acylating agent for enzymatic kinetic resolution of chiral amines

In this study, the activity of acetic acid esters modified with electron withdrawing 2-alkoxy-groups was investigated as acylating agent in kinetic resolution (KR) of racemic amines. A homologous series of the isopropyl esters of four 2-alkoxyacetic acids (2-methoxy-, 2-ethoxy-, 2-propoxy- and 2-butoxyacetic acids) were prepared and investigated for enantiomer selective N-acylation, catalyzed by lipase B from Candida antarctica, under batch and continuous-flow conditions. In the first set of experiments, isopropyl 2-propoxyacetate showed the highest effectivity with all of the four racemic amines [(±)-1-phenylethylamine, (±)-4-phenylbutan-2-amine, (±)-heptan-2-amine and (±)-1-methoxypropane-2-amine] in the set enabling excellent conversions (≥46%) and enantiomeric excess values (ee?≥?99%) with each amines in continuous-flow mode KRs under the optimized reaction conditions. In a second set of experiments, KRs of five additional amines – being substituted derivatives of (±)-1-phenylethylamine – further demonstrated the usefulness of isopropyl 2-propoxyacetate – being the best acylating agent in the first set of KRs – in KRs leading to (R)-N-propoxyacetamides with high ee values (≥99.8%).     

α,β-Dehydrogenation of esters with free OH and NH functionalities via allyl-palladium catalysis

A direct and selective method for the α,β-dehydrogenation of esters using palladium catalysis in the presence of free OH and NH functionalities is reported herein. Allyl-palladium catalysis allows for preservation of readily oxidizable functionalities such as amines and alcohols. Furthermore, an economical protocol using LDA was developed for the dehydrogenation of β-amino esters.     

Iridium-catalyzed asymmetric hydrogenation of β-keto esters with f-amphox ligands

The iridium-catalyzed asymmetric hydrogenation of β-keto esters with chiral tridentate P,N,N-ligands (f-amphox) has been developed. Under the optimized conditions, a wide range of β-keto esters can be hydrogenated smoothly, affording the corresponding β-hydroxy esters in good to excellent enantioselectivities (up to 95% ee).     

Thermische analyse binärer systeme von mesogenen cholesterylestern und azoxybenzolen

Zusammenfassung Die binären Systeme von Cholesterylnonanoat und 4,4-Bis(hexyloxy)azoxybenzol (1) und mit 4,4-Bis(heptyloxy)azoxybenzol (2) besitzen induzierte smektischeA-Phasen mit Umwandlungspunktmaximum. Während bei (1) die smektischeA-Phase beim Erhitzen in ihrem ganzen Existenzbereich zur cholesterischen Phase umgewandelt wird, ist bei (2) das Maximum gegenüber der cholesterischen Phase stabilisert und geht direkt in die isotrope Schmelze über. Beide Maxima weisen das Molverhältnis 11 auf. Im System (2) tritt außerdem eine smektischeC-Phase auf. Cholesterylhexadecanoat bildet mit Cholesterylnonanoat (3) und mit Cholesteryltetradecanoat (4) smektische und cholesterische Mischkristallreihen nach Typus I bzw. III Roozeboom. Durch die relative Stabilisierung von instabilen Festkristallmodifikationen der Komponenten in bestimmten Mischung sbereichen kommt es zur Ausbildung zusätzlicher, metastabiler Eutektika, die sich z.T. nicht in die thermodynamisch stabilen Formen umwandeln lassen. Dadurch ist es bei früheren Untersuchungen zu Irrtümern gekommen. In den Systemen (1) bis (3) bilden die Festkristalle einfache Eutektika, im System (4) Mischkristalle nach Typus V Roozeboom.

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The binary systems of cholesteryl nonanoate with 4,4-bis(hexyloxy)azoxybenzene (1) and with 4,4-bis(heptyloxy)azoxybenzene (2) show induced smecticA phases with transition point maximum. Whereas in (1) the smecticA phase is transformed into the cholesteric phase on heating within the whole range of its existence, in (2) the maximum of the smectic phase is stabilized compared with the cholesteric phase and clears into the isotropic melt directly. The molecular ratio of the maximum is 11 in both cases. Moreover in system (2) a smecticC phase was observed.Cholesterylhexadecanoate forms series of smectic and cholesteric mixed crystals of type I resp. III Roozeboom with cholesteryl nonanoate (3) and with cholesteryl tetradecanoate (4). As the unstable solid modifications of the components become relatively stabilized in some mixtures, additional metastable eutectics are formed, which hardly allow to be transformed into the thermodynamic stable solid crystals. Thus errors happened at previous investigations. In the systems (1) to (3) the solid crystals show simple eutectics, in system (4) mixed crystals type V Roozeboom are formed.