双通道毛细管离子色谱法同时测定降水中阴、阳离子

采用离子色谱法测定降水中的阴阳离子。F–,Cl–,NO2–,NO3–,SO42–,PO43–6种阴离子的检出限在0.002~0.015 mg/L之间,Na+,NH4+,K+,Mg2+,Ca2+5种阳离子的检出限在0.010~0.025 mg/L之间。阴离子加标回收率在88.4%~109%之间,相对标准偏差小于5%;阳离子加标回收率在85.0%~112%之间,相对标准偏差小于7%。用离子色谱法测定降水中的阴阳离子,操作简单、快捷,灵敏度高。     

整体柱离子相互作用色谱快速分析无机阴离子

研究了用硅胶整体柱和直接电导检测的离子相互作用色谱快速分析常见无机阴离子的方法。实验采用氢氧化四丁铵和邻苯二甲酸为淋洗液,讨论了包括淋洗液浓度、流速和pH对分离的影响。当以1.5 mmol/L氢氧化四丁铵和1.1 mmol/L邻苯二甲酸为淋洗液(pH 5.5),流速6 mL/min时,可以在1 min内分离Cl-、NO2-、Br-、NO3-、ClO3-、SO42-和I-7种阴离子。方法的检出限为0.3~1.9 mg/L,峰面积、峰高的相对标准偏差(RSD,n=5)分别为0.4%~2.2%和0.1%~1.5%。将该法用于测定矿泉水和地下水中的阴离子,加标回收率在97.9%~100.3%之间。     

梯度淋洗离子色谱法同时检测西兰花中6种无机阴离子

构建一种利用梯度淋洗离子色谱技术分析西兰花中Cl^-、Br^-、NO₂^-、NO₃^-、PO₄^3-和SO₄^2-6种无机阴离子含量的方法。梯度淋洗色谱离子体系为DIONEX Ion Pac AS11-HC(4 mm×250 mm)色谱柱,流速1.0 mL/min,抑制器电流80 mA,KOH淋洗液梯度淋洗。6种阴离子线性相关系数0.9995~0.9999,相对标准偏差(RSD)<2.5%,加标回收率95.7%~104%。用于检测西兰花中无机阴离子的方法灵敏度高、回收率高、可以适用于西兰花中6种阴离子精确定量分析。     

离子色谱法测定南京市道路灰尘中的四种无机阴离子

采用离子色谱法测定南京市道路灰尘中无机阴离子F^-、Cl^-、SO4^2-、NO3^-的含量。道路灰尘样品过150μm孔径的筛网,经3次涡旋离心提取,再取上清液高速离心,0.22μm滤膜过滤后上离子色谱测定。离心后的样品经IonPacTMAS 11-HC(250 mm×4 mm)色谱柱分离,以NaOH溶液(25 mmol/L)为淋洗液,采用电导检测器检测。4种阴离子均具有较宽的线性范围(0.01~0.20 mg/L),其线性相关系数r≥0.999。样品的加标回收率在87.4%~95.2%,仪器相对标准偏差(RSD)均≤3.5%,方法相对标准偏差(RSD)均≤7.7%。方法具有分析速度快,精密度好等优点,可用于评价南京市城区道路灰尘中的四种无机阴离子水平。     

直接电导检测-离子色谱法分离测定氟硼酸根及常见无机阴离子

研究了直接电导检测-离子色谱法分离测定BF4-及常见无机阴离子(F-、Cl-、Br-、NO3-、SO24-)。实验采用Shim-pack IC-A3阴离子交换色谱柱,分别选用邻苯二甲酸氢钾、对羟基苯甲酸 三(羟甲基)氨基甲烷 硼酸、邻苯二甲酸 三(羟甲基)氨基甲烷为淋洗液,考察了淋洗液种类、浓度、色谱柱温度、流速对分离测定BF4-及常见无机阴离子的影响。确定最佳色谱条件为:以1.25 mmol/L邻苯二甲酸氢钾为淋洗液,流速1.5 mL/min,柱温45℃。在此条件下可同时基线分离6种阴离子,且色谱峰形对称。所测阴离子的检出限为0.02~0.58 mg/L;峰面积的相对标准偏差(RSD,n=5)小于0.8%。将方法应用于测定离子液体中的BF4-及其它无机阴离子,加标回收率在98.2%~102.7%之间。     

离子色谱法测定电厂水中的有机酸和无机阴离子

建立离子色谱梯度淋洗抑制电导法测定电厂水中有机酸和无机阴离子的方法。选用Ion Pac AG11–HC(50 mm×4 mm)阴离子保护柱和Ion Pac AS11–HC(250 mm×4 mm)阴离子分析柱对样品进行分离,以氢氧化钾溶液梯度淋洗,自再生抑制电导检测器检测,同时测定电厂水中的有机酸和无机阴离子。F–,Cl–,NO2–,Br–,NO3–的线性范围为0.005~2 mg/L,CH3COO–,HCOO–,SO42–,PO43–的线性范围为0.01~5 mg/L,各组分线性相关系数为0.998 9~0.999 3,检出限为0.122~0.989 ng/m L,测定结果的相对标准偏差小于2.0%(n=7),样品加标平均回收率为97.9%~101.7%。该方法操作简便,实用性强,可以用于电厂水中有机酸和无机阴离子的检测。     

离子色谱法测定乙二醇中微量有机酸和无机阴离子

建立了以YSA-8阴离子交换柱的离子色谱法分析乙二醇中微量有机酸和无机阴离子的方法,比较了进样乙二醇浓度对F-及有机酸测定结果的影响,进样乙二醇质量分数低于8.5%时,能够得到较准确的数据.用本法对所测的有机酸和无机阴离子检出限均在8.9 μg/L以下,线性相关系数r在0.996～0.999范围内,标准样中各物质的离子峰面积的相对标准偏差(RSD)在4.2%以下(n＝11),对乙二醇质量分数约为8.5%的样品中F-及有机酸的加标回收率在91.6%～100.0%之间,乙二醇含水料直接测定无机阴离子的加标回收率在91.8%～104.8%之间.     

离子色谱法同时测定土壤中Cl-、SO42-和 NO3-

利用离子色谱法同时测定土壤中的Cl^-、SO4^2-、NO3^-三种无机阴离子。采用30 mmol/L KOH淋洗液在1.2 mL/min流速下对Cl^-、SO4^2-、NO3^-三种无机阴离子进行分离测定,混合标准溶液的相对标准偏差为0.16%~0.84%,三种阴离子的线性范围都在0~150 mg/L,线性相关系数均大于0.999。三种阴离子的检出限分别是0.062、0.096和0.064 mg/L。对四种国家标准物质的测定结果表明(n=9),测定值与标准值一致,相对标准偏差(RSD)<3%,三种阴离子的加标回收率为95.6%~109%。采用离子色谱法测定土壤中的Cl^-、SO4^2-、NO3^-三种无机阴离子,方法简便、快捷、无污染,对人体无任何伤害,真正实现了绿色化学的分析要求。在6 min以内完成分析,适合大批量土壤水溶盐阴离子的测定。     

抑制型电导检测离子色谱法测定饮用水中的痕量溴酸盐

建立一种直接进样测定饮用水中痕量溴酸盐的电导检测离子色谱法。选用Metrosep A Supp 5阴离子交换分离柱,碳酸盐淋洗液。抑制型电导检测采用化学抑制器和CO2抑制器顺序双抑制系统。实验结果显示,溴酸根阴离子与常见共存阴离子完全分离,溴酸盐含量在5~100 μg/L范围内具有良好的线性(r=0.9999),精密度高(相对标准偏差（RSD）<4%),方法的检出限为0.50 μg/L,样品加标平均回收率为96.1%~107%。该方法操作简单,分离效果好,可与常见阴离子实现同时分析,灵敏度高,重现性好,可作为饮用水中溴酸盐的标准测定方法。     

离子色谱法测定苦荞系列产品中4种无机元素

采用离子色谱法同时测定苦荞粉、苦荞壳、苦荞叶、苦荞杆中Na、K、Ca、Mg等4种元素含量,并对元素进行了对比研究,同时对各元素进行了加标回收实验,苦荞粉、苦荞壳、苦荞叶、苦荞杆中各元素的平均回收率在94.00%~102.7%,相对标准偏差(RSD)在0.88%~2.8%,测定范围为0.89~999.10μg/L。实验建立了简便、快速、准确和稳定的测定苦荞粉、苦荞壳、苦荞叶、苦荞杆中无机元素的方法。结果显示苦荞叶中Ca和Mg的含量均很高,分别为17 208.8mg/kg和3 954.5mg/kg,苦荞壳中钾和钠含量很高,分别为4 849.1mg/kg和1 269.2mg/kg;在苦荞叶中Ca、Mg等营养元素的含量较苦荞粉中的高,所以苦荞叶有开发应用价值。     

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.     

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.     

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.     

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.     

α-Amino acid derived enaminones and their application in the synthesis of N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates and other heterocycles

A new and simple synthesis of novel N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates, which exist in equilibrium with their 4-oxo tautomers, has been developed in two steps starting from N-protected α-amino acids. The key intermediates are enaminones, which can also be isolated, characterized, and used for the construction of other functionalized heterocycles, before they spontaneously decompose to pyrrole products. 4-Hydroxypyrroles are prone to partial aerial oxidation but can be efficiently alkylated or reduced to stable polysubstituted pyrrolidine derivatives.     

Specific intramolecular aromatic CH insertion of diazosulfonamides

The chemoselectivity in the intramolecular CH insertion of various diazosulfonamides has been experimentally studied. The results reveal that the aliphatic 1,4-, 1,5-, or 1,6-C(sp³)?H insertions of diazosulfonamides are not accessible, while the aromatic 1,5-C(sp²)?H insertion can be realized specifically by adjusting the diazo-adjacent group. In addition, the general chemoselectivities in the intramolecular CH insertions of diazosulfonyl compounds are summarized. Generally, diazosulfones undergo both aromatic 1,5-C(sp²)?H and aliphatic 1,5- and 1,6-C(sp³)?H insertions, while diazosulfonates undergo aliphatic 1,5- and 1,6-C(sp³)?H insertions. However, diazosulfonamides only undergo aromatic 1,5-C(sp²)?H insertion.     

Microwave-assisted copper-catalyzed stereoselective ring expansion of three-membered heterocycles with α-diazo-β-dicarbonyl compounds

Microwave-assisted copper-catalyzed ring expansions of three-membered heterocycles with α-diazo-β-dicarbonyl compounds were investigated. Thiiranes generated 3-acyl-5,6-dihydro-1,4-oxathiines in the presence of copper sulfate and trans-3-acyl-5,6-dihydro-1,4-oxathiines as stereospecific products for 1,2-disubstituted cis-thiiranes through an intramolecular S_N2 process. Oxiranes gave rise to 2-acyl-5,6-dihydro-1,4-dioxines under the catalysis of copper hexafluoroacetylacetonate and cis-3-acyl-5,6-dihydro-1,4-dioxines as stereospecific products for 1,2-disubstituted cis-oxiranes via an intimate ion-pair mechanism. The current method provides a direct and simple strategy in efficient preparation of 3-acyl-5,6-dihydro-1,4-oxathiines and 2-acyl-5,6-dihydro-1,4-dioxines, important agents in medicinal and agricultural chemistry, from readily available thiiranes and oxiranes, respectively.     

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.     

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.