微波消解-电感耦合等离子体原子发射光谱法测定两种奶茶粉中微量元素

以微波消解系统对奶茶粉样品进行处理,并采用电感耦合等离子体发射光谱法(ICP-AES)对样品中的微量元素进行测定。优化了仪器工作条件,建立了同时测定奶茶粉中Zn、Fe、Cu、Mn、Cd、As、Ba和Pb 8种元素的微波消解-ICP-AES法。平均回收率为97.1%～103.2%之间,相对标准偏差(RSD)在0.7%～3.6%之间。实验结果表明,方法简便、快速、准确,适用于奶茶粉样品中微量元素的测定。     

测定川芎中有害金属元素的三种样品前处理方法的比较试验

用3种不同的样品前处理方法,即①常规湿法酸消解法、②微波加热酸消解法及③干灰化法分别对川芎样作前处理溶解,用石墨炉原子吸收光谱法(GF-AAS)测定试液中铅、铜和镉的含量,用氢化物发生-原子荧光光谱法(HG-AFS)测定试液中砷和汞的含量。结果表明:用方法①及方法③处理样品所得溶液中,铅、铜和镉的回收率在83.0%～121.0%之间,而汞和砷的回收率很低。在方法②处理样品所得溶液中,测得砷、铜、镉及汞的回收率达97.0%～127.0%之间,而铅的回收率较低,仅为51.8%。总之,方法①适合用于GF-AAS测定铅时的样品前处理,方法②宜用于HG-AFS测定汞和砷时的样品前处理,而方法③宜应用于GF-AAS测定铜及镉时的样品前处理。     

便携式X射线荧光光谱法在化肥砷、隔、铅、铬、汞快速检测中的应用

为评估便携式X射线荧光光谱法(PXRF)对化肥中砷、隔、铅、铬、汞五种重金属含量测定的可靠性,使用PXRF法分别对4个模拟污染化肥样品,以及在全国11个省、直辖市或自治区抽样的103个化肥样品进行测定,与肥料检测国家标准(GB/T 23349-2020)中实验室分析方法的测定结果进行了比较。结果表明：PXRF法对模拟污染化肥样品中As、Cd、Pb元素测定的准确度在90% ~ 115%之内,相对标准偏差小于10%,对Cr的测定准确度在115% ~ 140%之间,相对标准偏差在3.99% ~ 15.83%之间,对Hg的测定准确度在70% ~139%之间,相对标准偏差在3.68% ~ 9.37%之间。PXRF法测定的结果与实验室分析法所确定的参考值有较好的相关性,R2 在0.8906 ~ 0.9816之间,PXRF法各元素的最低检出含量低于国家标准限值或与之相当。因此PXRF法能满足肥料中五种重金属含量的快速筛查要求,可作为辅助手段用于肥料重金属污染抽查,有效减少抽样量,提高抽样效率。     

ICP-AES法测定茶叶中As,Cd,Ni,Pb等元素的含量

目的对样品前处理、酸度及茶叶中共存元素干扰的影响等因素进行探讨,方法用微波消解前处理样品,ICP-AES法同时测定茶叶中铅(Pb)、砷(As)、镉(Cd)、镍(Ni)等元素含量。结果该法的回收率在84.5%～115%之间,精密度RSD均小于9%,结论该法能满足茶叶测定要求。     

重铬酸钾容量法测定地质样品中的有机碳

目前,地质样品中有机碳的测定方法有干烧法（高温电炉灼烧）和湿烧法（重铬酸钾氧化）两大类。另外还有ICP-AES法、微波消解法、过硫酸钾法、电导法、石墨电热消解法、比色法等,然而这些有机碳测定方法仍然存在许多不尽如人意的地方。干烧法要求实验条件苛刻,操作繁琐,不易掌握,受碳酸盐的干扰。湿烧法虽然操作比较简单,但方法受样品中还原性物质的干扰,如氯根、亚铁等,上述方法都有待完善和优化改进。如：探索因不同样品基体差异而产生的干扰元素消除方法;寻找更合适的指示剂;本文采 用重铬酸钾-容量法测定地质样品中的有机碳,在220±10℃恒温电热板上,用0.4 mol/mL重铬酸钾溶解样品。通过优化熔矿温度、熔矿时间、熔剂浓度的优化选择,进行了氯离子的干扰试验。样品中含氯化物低的样品通过加入0.1 g硫酸银消除,样品中含氯化物高的样品通过高温灼烧减量消除。氧化指示剂选用邻菲啰啉或苯二氨基苯甲酸。本方法适用于土壤、水系沉积物、岩石等地质调查样品中有机碳的测定,方法相对标准偏差（RSD）在0.80%～4.41%之间,准确度（RE）在-3.15%～+1.15%之间。通过标准物质验证,方法技术指标满足地质行业规范DZ/T0130.4-2006中有机碳的分析要求,建立了一种简单、快捷、经济、准确的测定地质样品中有机碳的测定方法,满足地球化学调查批量样品生产的需要。     

原子吸收光谱法测定赣南产艾叶中六种金属元素含量

目的运用火焰原子吸收光谱法对赣南产艾叶中Fe、Zn、Cu、Mg、Ca和Mn 6种金属元素进行了测定。方法用浓HNO_3-H_2O_2处理样品,采用标准曲线法测定。结果所测定的样品中含有丰富的人体必需金属元素,采用此法回收率在90.00%~101.25%之间,样品相对偏差小于10%。结论该法简单、准确,结果令人满意。     

原子荧光光谱法测定色母粒中铅含量

建立了原子荧光光谱仪测定色母粒中铅的方法。将色母粒样品置于电炉中炭化,然后以HNO3–HClO4洗涤样品残渣,再加热使余酸挥发,通过控制余酸的量使试样溶液的酸度保持在0.8%~1.3%之间,用原子荧光光谱仪对样品消解液进行检测。该方法测定结果的相对标准偏差在3.66%~7.52%之间,加标回收率在82%~120%之间。与电感耦合等离子体光谱法、原子吸收光谱法和电感耦合等离子体质谱法等进行比对检测,检测结果在允许误差之内。     

微波消解-电感耦合等离子质谱法同时测定烟用香精中24种微量元素

采用微波消解处理样品,电感耦合等离子体质谱检测的方法同时测定了8种烟用香精样品中的24种微量元素。方法以锗和钍作为内标消除基体效应,采用灌木枝叶标准物质(GBW07602)对方法进行验证。结果表明:24种微量元素的检测限在0.004～1.078ng/mL之间;相对标准偏差均小于10%;回收率在84.46%～108.85%之间。该法操作简单、分析快速、灵敏度高、准确度好,适合批量香精样品中微量元素的检测。     

不同消解方法对火焰原子吸收光谱法测定乳制品中无机元素含量的影响

取鲜奶及酸奶样品分别用3种不同的消解方法(即常规湿法酸消解法、微波加热酸消解法和干法消解法)做预处理。在所得最终的试样溶液中分别用火焰原子吸收光谱法测定其中6种无机元素(即钙、镁、铜、锌、铁及锰)。试验结果表明:采用微波加热酸消解法处理的样品,6种元素的回收率可达94.5%～100.0%高于其他两种方法的回收率最高值,相关测定值的相标准偏差(n=6)在1.9%～4.2%之间。因此,用火焰原子吸收光谱法测定乳制品中无机元素含量时,用微波加热酸消解法处理样品的效果较好。     

阴离子交换树脂分离-原子荧光法测定色母粒中的镉

采用微波消解溶样,结合离子交换法对色母粒样品进行待测元素的提取及净化处理,利用原子荧光光度计进行镉含量的测定。研究了717型阴离子交换树脂对色母粒样品中镉的吸附及分离条件,解决了样品中铅、铜等元素的干扰问题。方法加标回收率在92.4%～117.4%之间,相对标准偏差小于3.0%。     

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%.     

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.     

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.     

A general and convenient synthesis of 4-(tosylmethyl)semicarbazones and their use in amidoalkylation of hydrogen,heteroatom, and carbon nucleophiles

A general synthesis of previously unknown semicarbazone-based α-amidoalkylating reagents, 4-(tosylmethyl)semicarbazones, has been developed. The synthesis involved three-component condensation of semicarbazones of aliphatic or aromatic aldehydes with the same or other aldehydes and p-toluenesulfinic acid. The scope and limitations of this reaction were investigated. The compounds obtained were demonstrated to be an efficient α-(4-semicarbazono)alkylating agents. They were reacted with H- (sodium borohydride), O- (sodium methylate), S- (sodium phenylthiolate), N- (pyrrolidine, sodium succinimide), P- (trialkyl phosphites), and C-nucleophiles (sodium diethyl malonate) to give the corresponding products of the tosyl group substitution, 4-substituted semicarbazones, including analogues of nitrofurazone. Among the prepared compounds tested in vitro for antibacterial and antifungal activity, three nitrofuryl-containing semicarbazones exhibited high biological activities with minimum inhibitory concentration (MIC) values of 8–32 μg/mL.     

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.     

Synthesis of novel chiral bidentate hydroxyalkyl-N-heterocyclic carbene ligands and their application in palladium-catalyzed Mizoroki–Heck couplings and asymmetric addition of diethylzinc to benzaldehyde

A small library of new chiral bidentate hydroxyalkyl-imidazolium salts 1 is conveniently synthesized on multi-gram scale from inexpensive and commercially available chiral pool amino acids. The corresponding carbenes, generated by deprotonation of imidazolium salts 1, in combination with palladium(II) chloride were tested in the Mizoroki–Heck coupling reaction. The most significant results in terms of yields and reactivities were achieved with low catalyst loading. The catalytic activities of these imidazolium salts were also investigated in the asymmetric addition of diethylzinc to benzaldehyde. The use of MgO nanoparticles as an additive in conjunction with these ligands played a crucial role in increasing the efficiency of these reactions.