土壤及蔬菜中微量汞的同位素稀释电感耦合等离子体质谱测定

建立了微波消解电感耦合等离子体质谱同位素稀释(ID/ICP-MS)测定微量汞的方法。考察了仪器参数及测量条件对汞同位素比值RHg(202Hg/200Hg)测量的影响,根据同位素比值测量误差的传递因子优化了富集同位素稀释剂(202Hg98%)的加入量,并以铊同位素比值(205Tl/203Tl)作为RHg(202Hg/200Hg)测量时发生质量歧视效应的校正因子;通过反同位素稀释法标定了富集汞同位素稀释剂的浓度。利用所建立的ID/ICP-MS方法测定了杨树叶(GBW07604)和湖积物(GBW07423)2种标准参考物中汞的含量,回收率分别为112%和100%。该方法具有准确度高、精密度好等优点,且样品前处理简便,适用于土壤及蔬菜等样品中微量及痕量汞的准确测定。     

同位素稀释-液相色谱-电感耦合等离子质谱(ICP-MS)法测定大米中的甲基汞

目前国标方法GB 5009.17—2021测量样品中甲基汞(含量≤0.1 mg/kg)的精密度为20%、定量限为0.02 mg/kg,对于定量限以下的样品检测存在困难;为了能精确地测量国家食品安全检测领域关注的甲基汞污染物,通过在样品中加入同位素稀释剂后以GB 5009.17—2021国标方法进行样品前处理,以液相色谱分离出汞形态,用ICP-MS检测同位素比值,考虑质量歧视效应后以同位素稀释质谱法定量,建立了同位素稀释-液相色谱-电感耦合等离子质谱法测定大米样品中甲基汞含量的方法。当样品中甲基汞含量在0.01~0.03 mg/kg时,方法的精密度为0.3%~22.8%,不确定度U为0.002~0.004 mg/kg,k=2。以鱼肉中总汞与甲基汞成分分析标准物质(GBW10029)作为质控样,测定得到三种大米样品中甲基汞含量(以Hg计)分别为(8±2)、(24±3)、(19±4) ng/g,经过不确定度评估后表明方法的准确度较高;质控样(GBW10029)甲基汞的证书值(以Hg计)为 (0.84±0.03) mg/kg,而测量结果为(0.83±0.08) mg/kg,对质控样的测量结果说明该方法可靠;同位素稀释法将浓度的测量转换成同位素的丰度比的测量,可避免前处理过程带来的误差,同位素稀释与质谱结合可用于大米中甲基汞的高精度分析。     

土壤中总汞测量不确定度的评定

依据JJF1059-1999,对GB/T17136-1997冷原子吸收分光光度法测定土壤中总汞含量进行了不确定度评定。建立了数学模型,对各不确定度分量进行分析和量化。计算出土壤中总汞含量测量结果的相对合成标准不确定度为0.0215,扩展不确定度为0.163mg/kg。在土壤总汞含量测量过程中,求试液中汞含量贡献的不确定度最大。     

超声水浴-王水浸提-全自动测汞仪测定重度污染土壤中的总汞

为准确测定重度污染土壤中的总汞含量,本文建立了以超声水浴辅助王水浸提,使用全自动测汞仪测定的方法。 通过单因素实验考察了王水用量、超声时间和超声温度对土壤中总汞测定的影响,得到最佳前处理方法,最后应用建立的方法对重度污染土壤进行方法验证。确定了0.5 g土壤样品中加入5 mL的王水溶液,放入超声波清洗器中70℃水浴下超声提取70 min,使用超纯水定容至50mL的前处理方法,直接进样测定的实验方法。对该实验进行验证,结果表明,该方法汞低标准曲线汞含量在0～20ng范围内线性良好,相关系数R=0.9995;汞高标准曲线汞含量在20～150 ng范围内线性良好,相关系数R=0.9993;方法检出限为0.0055 mg/kg,方法定量下限为0.022 mg/kg;通过对土壤样品及土壤加标样品的测定,回收率为90.40～116.80%,表明该方法的准确度较高,RSD为1.89～3.34%（n=6）,表明该方法的精确度较高。超声水浴-王水浸提-全自动测汞仪法用于测定重度污染土壤中的总汞,前处理简单,自动化程度较高,可快速,高效的用于重度污染土壤总汞测定工作。     

高效液相色谱-电感耦合等离子体质谱联用测定生物样品中无机汞和甲基汞

建立了高效液相色谱(HPLC)和电感耦合等离子体质谱(ICP-MS)联用测定多种生物样品中的无机汞和甲基汞的方法,并对比了提取生物样品中无机汞和甲基汞的不同前处理方法。实验使用5 mol/L的盐酸超声波提取样品中的无机汞和甲基汞。高效液相色谱流动相为含有0.06 mol/L醋酸氨,20μg/L B i,0.1%(V/V)2-巯基乙醇的5%(V/V)甲醇-水溶液,色谱柱为C18反相柱(5μm,3.9 mm×150 mm)。提取液在液相色谱中分离后,进入电感耦合等离子体质谱检测其中无机汞和甲基汞的浓度。测定了人发(GBW 07601),对虾(GBW 08572),鱼肉组织(IAEA MA-B-3/TM)和牛肝(GBW 080193)4种生物标准参考物,结果与标准参考物的标准值相符。无机汞和甲基汞检出限分别为0.3和0.2μg/L。     

高效液相色谱法测定婴幼儿用奶瓶中己内酰胺迁移量的不确定度评定

采用高效液相色谱法测定婴幼儿用奶瓶中己内酰胺迁移量,并对其测定的结果进行不确定度的评估。参照JJF 1059.1—2012 《测量不确定度评定与表示》和CNAS—GL 006：2019 《化学分析中不确定度的评估指南》中的规定与要求,分析己内酰胺在测定过程中的各种不确定度来源。水基食品模拟物处理的样品中己内酰胺的迁移量测定结果为12.213 mg/L,其扩展不确定度为1.29 mg/L,结果表示为(12.21±1.29) mg/L,k=2;酸性食品模拟物处理的样品中己内酰胺的迁移量测定结果为15.608 mg/L,扩展不确定度为1.48 mg/L,结果表示为(15.61±1.48) mg/L,k=2;酒精类食品模拟物处理样品中己内酰胺所产生的迁移量测定结果为18.299 mg/L,扩展不确定度为1.84 mg/L,结果表示为(18.30±1.84) mg/L,k=2;油基食品模拟物处理样品中,己内酰胺的迁移量测定结果为10.232 mg/kg,扩展不确定度为0.99 mg/kg,结果表示为(10.23±0.99) mg/kg,k=2。通过评估发现,不确定度主要的影响因素是标准溶液的配制...     

电感耦合等离子体质谱法测定食用植物油中铅、总砷含量不确定度评定

采用电感耦合等离子体质谱法(ICP-MS)测定食用植物油中铅(Pb)、总砷(As)含量,对测定结果的不确定度进行评定。利用ICP-MS,采用标准加入法测定食用植物油中Pb,As含量,分析测定过程中不确定度来源,包括样品称量、定容、前处理、溶液中Pb和As浓度、重复性测量等引入的不确定度,计算合成不确定度。结果表明,Pb含量为(0.0228±0.013) mg/kg,k=2;As含量为(0.00785±0.0045) mg/kg,k=2。该方法的不确定度主要来源于样品溶液中的Pb,As浓度,评定得到的不确定度可为正确评价测定结果提供科学依据。     

稳定同位素稀释-气相色谱质谱联用法测定水产品中甲基汞和乙基汞

建立了测定水产品中甲基汞和乙基汞的气相色谱质谱联用分析方法。采用6.0 mol/L HCl超声辅助提取,在NaCl存在下,提取液中甲基汞和乙基汞可被甲苯萃取,再用半胱氨酸反萃取,加入CuSO4释放出的甲基汞和乙基汞与四苯硼钠反应,生成甲基苯基汞和乙基苯基汞,经DB-5MS毛细柱分离,选择离子监测方式(SIM)质谱检测,以d3-甲基汞作为内标的稳定同位素稀释法定量。甲基汞和乙基汞标准曲线的线性范围均为1~500μg/L,国家标准参考物质(GBW 10029)6次测定的甲基汞(以汞计)平均值为0.828 mg/kg,相对标准偏差为3.2%,与证书参考值(0.84±0.03)mg/kg(以汞计)一致。鱼、虾和贝类等不同种类水产品中甲基汞和乙基汞的平均加标回收率分别为94%~101%和81%~104%,相对标准偏差在1.9%~4.7%和3.1%~8.2%范围内(n=6),样品的检出限为0.1~0.3μg/kg(S/N=3)。方法灵敏,准确,可用于水产品中甲基汞和乙基汞的测定。     

液相色谱–同位素稀释质谱法测定人体生长激素

建立了准确、快速测定痕量人体生长激素的同位素稀释质谱法。选取同位素标记脯氨酸、缬氨酸和苯丙氨酸为内标物,将内标物以重量法与待测样品准确混合,利用Kinetex C18色谱柱分离,以电喷雾三重串联四级杆质谱多反应监测模式测定,建立了人体生长激素的液相色谱–同位素稀释质谱联用定量方法。人体生长激素溶液标准物质的含量测定结果为(1.82±0.04)mg/g,相对标准偏差为0.43%(n=6)。该方法简易、实用、准确、可靠,可作为人体生长激素溶液标准物质的定值方法,并为人体生长激素的日常检测提供参考。     

高效液相色谱-非特异性同位素稀释质谱联用技术定量分析全血中总血红蛋白含量

建立了基于同位素稀释(ID)的高效液相色谱(HPLC)-电感耦合等离子体质谱(ICP-MS)联用技术,通过测量血红蛋白(HGB)中铁(Fe)元素含量实现了全血中总HGB准确定量的策略.该策略包括2种方法,第一种方法为在线HPLC-ID-ICP-MS定量技术:全血中HGB经液相色谱分离后,通过柱后在线添加浓缩54Fe同位素稀释剂的方式,与液相色谱洗脱液经三通混合后进入ICP-MS在线测量54Fe/56Fe的同位素比值,并根据同位素稀释质谱法公式及蛋白中Fe的含量计算HGB的浓度.针对全血样品中存在的其它主要含铁蛋白[如转铁蛋白(Tf)],在实现色谱完全分离的基础上,通过在线优化改变54Fe稀释剂流速实现了HGB和Tf的同时定量.在另一种方法中,先对全血样品进行消解并通过ID-ICP-MS测定其中Fe的总量,然后根据全血样品的HPLC-ICP-MS分析结果,通过计算HGB质谱峰面积占总峰面积的比值从而得到HGB中Fe含量占总Fe含量的比例,实现了其中HGB的准确定量. 2种定量方法得到的结果分别为(115.3±2.4) mg/g和(115.5±2.1) mg/g,结果吻合良好,方法的检出限...     

二氧化碳和丙烯直接合成甲基丙烯酸的NiPMo/TiO2催化剂的研究

用溶胶-凝胶法以磷钼酸(MPA)的镍盐溶液水解钛酸四丁酯制备了NiPMo/TiO2催化剂.使用ICP、 XRD、 TG-DTA、 IR、 TPD-MS和微反应技术研究了催化剂的化学组成、热稳定性、化学吸附性质和催化反应性能.杂多钼酸盐与TiO2通过O2-在TiO2表面发生了键合.在623 K下,杂多阴离子仍保持原有的Keggin结构.CO2在Lewis酸位Ni(Ⅱ)和Lewis碱位Ni-O-Mo的桥氧协同作用下生成CO2卧式吸附态Ni(Ⅱ)←O-(CO)←(O--Ni).丙烯有多种吸附态在催化剂上吸附.在563 K、 1 MPa和空速1500 h-1的反应条件下,丙烯的摩尔转化率为3.2%,产物MAA选择性为95%.     

Toward new camptothecins. Part 6: Synthesis of crucial ketones and their use in Friedländer reaction

In the context of the preparation of camptothecin and luotonin A analogs, the synthesis of some key keto-precursors and their use in Friedländer condensation are described. This paper also focuses on the stability of these keto intermediates and emphasizes the major differences between indolizinones and pyrroloquinazolinones series. Noteworthy is also the report of some original structures isolated as by-products of some experiments.     

CoFe2O4自形成磁性液体场致结构化对磁化的影响

The Langevin paramagnetic theory can’t describe the relation between magnetization of ferrofluids and applied magnetic field. The structuralization of ferrofluids, which is considered the main influence factor of the magnetization, is regarded. The part of magnetization works is deposited when the structure is forming. This action influences the magnetization of ferrofluids directly or indirectly. On the base of the “compressing” model, the Langevin function that usually describes the magnetization of ferrofluid is modified, and a well-fitted curve is obtained. An equation of the relation between the equivalent volume fraction after being “compressed” and the intensity of magnetic field is discovered, which approximately describes the process of magnetization. The relation between the approximate initial susceptibility and the volume fraction can be obtained from modified formula.     

Highly regioselective Buchwald–Hartwig amination at C-2 of 2,4-dichloropyridine enabling a novel approach to 2,4-bisanilinopyridine (BAPyd) libraries

The highly regioselective Buchwald–Hartwig amination at C-2 of the cheap and readily accessible reagent, 2,4-dichloropyridine with a range of anilines and heterocyclic amines is described. This new methodology is robust and provides a facile access to 4-chloro-N-phenylpyridin-2-amines on 0.25 mol scale. These intermediates undergo a further Buchwald–Hartwig amination at higher temperature to enable rapid exploration of the chemical space at C-4 and to provide a library of 2,4-bisaminopyridines.     

KMnO4-mediated oxidative CN bond cleavage of tertiary amines: Synthesis of amides and sulfonamides

KMnO₄-mediated oxidative CN bond cleavage of tertiary amines producing secondary amine was introduced, which was trapped by electrophiles (acyl chloride and sulfonyl chloride) to form amides and sulfonamides. The reaction could take place at mild condition, tolerating a wide range of function groups and affording products in moderate to excellent yields.     

Chemistry of heterocyclic compounds at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences, over 50 years (Review)

The review contains a concise historical account and information on the most significant researches undertaken by the staff at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences on the Chemistry of Heterocyclic Compounds. Dedicated to Academician of the Russian Academy of Sciences B. A. Trofimov on his 70th jubilee. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1443–1502, October, 2008.     

Sulfur-directed metal-free and regiospecific methyl C(sp3)–H imidation of thioanisoles

Regiospecific and direct imidation of the methyl C(sp³)–H bond of thioanisoles is realized under mild and metal-free conditions with N-fluorobis(benzenesulfonyl)imide as an oxidant and nitrogen source. Proposed mechanism suggests that thionium ion intermediates and a Pummerer-type reaction are involved. The imidation has advantages such as high step-economy, excellent functionality tolerance, and regiospecificity, giving structurally diverse imidation products.     

Selective syntheses of 2H-1,3-oxazines and 1H-pyrrol-3(2H)-ones via temperature-dependent Rh(II)-carbenoid-mediated 2H-azirine-ring expansion

The Rh(II)-catalyzed reaction of 2-carbonyl-substituted 2H-azirines with ethyl 2-cyano-2-diazoacetate or 2-diazo-3,3,3-trifluoropropionate provides an easy access to 2H-1,3-oxazines and 1H-pyrrol-3(2H)-ones. These compounds can be selectively prepared from the same starting material using temperature as the only varied parameter. The 2-azabuta-1,3-diene intermediate, a common precursor for both heterocyclic products, isomerizes into 2H-1,3-oxazine under kinetic control, while 1H-pyrrol-3(2H)-one is the sole product of the reaction at elevated temperatures. According to DFT-calculations a one-atom oxazine ring contraction involving ring-opening to a 2-azabuta-1,3-diene intermediate, followed by a 1,5- and 1,2-prototropic shift leads to the consecutive formation of imidoylketene and azomethine ylide, which then further undergo cyclization to the pyrrole derivative.     

Synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives

Different approaches for the synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives from simple amino acids have been investigated. A library of 33 precursors for the preparation of N-hydroxy pyrazinones was obtained in moderate to good yields.