单柱离子色谱法测定钼酸根和钨酸根离子的研究

本文采有单柱离子色谱系统测定了MoO_4~(2-)和WO_4~(2-)。以1.0mmol/L钼酸钠为淋洗液测定WO_4~(2-),以1.0mmol/L钨酸钠为淋洗液测定MoO_4~(2-),常见阴离子Cl~-、NO_3~-、SO_4~(2-)不干扰测定,MoO_4~(2-)和MO_4~(2-)的检出限分别为3.55μg/ml和5.03μg/ml,相对标准偏差为1.04％和1.66％,工作曲线的线性范围为3.55～1500μg/ml和5.03～1500μg/ml。应用于钼、钨、硅杂多酸中钼和钨的测定,结果满意。     

固相萃取-离子色谱法测定地下水中痕量高氯酸根离子

建立了测定地下水中痕量高氯酸根（ClO~4）的固相萃取-离子色谱(SPE-IC)分析方法。0.7 L水样经预处理降低主要干扰离子Cl~、CO2~3和SO2~4的干扰后,使用Cleanert PWAX弱阴离子交换固相萃取小柱对地下水中痕量(μg/L级)的ClO~4进行富集,用6 mL 1%NaOH溶液洗脱,富集液经0.45 μm水膜过滤后,用IonPac AS20阴离子分离柱、50 μL进样环、40 mmol/L KOH溶液淋洗、抑制电导检测分离分析。结果表明,地下水样品中ClO~4的方法检出限和测定下限分别为0.15 μg/L和0.60 μg/L,进样质量浓度在1～15 μg/L范围内有很好的线性关系,线性相关系数为0.9992,回收率为99.7%～100.5%;该方法经济有效,可用于地下水中痕量ClO~4的检测。利用该方法测定了哈尔滨周边部分地区地下水中ClO~4浓度,检测结果与离子色谱-质谱联用法的检测结果的相对误差为1.85%～9.24%。     

离子色谱法检测烟叶中的NO3-、NO2-、Cl-

研究了离子色谱法检测烟叶中阴离子的方法。采用美国Dionex公司DX－500型离子色谱仪，以3.5mmol/L Na2CO3-1.0mmol/L NaHCO3作为淋洗液，流速为1.2mL/min，测定烟叶中的NO3^-、NO2^-、Cl^-等阴离子含量。各种离子在检测条件下有很好的线性，相关系数r=0.9986-0.9997,NO3^-、NO2^-和Cl^-的检出限分别为0.200、0.125和0.064μg/mL。     

离子色谱法测定核电站一回路冷却剂中痕量F~-,Cl~-和SO_4~(2-)

建立离子色谱法测定核电站一回路冷却剂中痕量氟离子F~-,氯离子Cl~-,硫酸根离子SO_4~(2-)的方法。采用80 mmol/L硼酸溶液配合氢氧化钾淋洗液发生器在线生成淋洗液,梯度洗脱,淋洗液流量为1.2 mL/min,在选定的分析条件下,NO_2~-,NO_3~-,PO_4~(3-)和CO_3~(2-)不干扰F~-,Cl~-,SO_4~(2-)的测定。F~-,Cl~-,SO_4~(2-)的质量浓度与其色谱峰面积呈良好的线性关系,线性相关系数分别为0.999 8,0.999 5,0.999 7,线性范围分别为0.85~30.0,2.65~30.0,2.00~30.0μg/L。F~-,Cl~-,SO_4~(2-)测定结果的相对标准偏差分别为0.56%~1.58%,0.85%~3.62%,1.21%~4.60%(n=7)。F~-,Cl~-,SO_4~(2-)的加标回收率分别为98%~104%,98%~108%,93%~108%。该方法快速、准确,满足核电站一回路冷却剂中痕量F~-,Cl~-,SO_4~(2-)的检测要求。     

离子色谱法同时分析离子液体中三氟乙酸根、四氟硼酸根和三氟甲烷磺酸根

建立了离子色谱-直接电导检测法同时测定离子液体中三氟乙酸根、四氟硼酸根和三氟甲烷磺酸根的方法。色谱分离采用Shim-packIC-A3阴离子交换色谱柱和邻苯二甲酸氢钾淋洗液。最佳色谱条件为:以邻苯二甲酸氢钾(1.2mmol/L)为淋洗液,柱温30℃,流速1.0mL/min。在此条件下,所测阴离子的检出限为0.06～3.07mg/L,保留时间和峰面积的相对标准偏差(n=5)分别不大于0.18%和1.62%。用来测定离子液体中三氟乙酸根、四氟硼酸根和三氟甲烷磺酸根,加标回收率为98.2%～101.8%,能够满足离子液体中的三氟乙酸根、四氟硼酸根和三氟甲烷磺酸根定量分析要求。     

十四烷基苄基氯化铵共振散射光谱法测定亚氯酸根

在乙酸钠-盐酸缓冲溶液中,亚氯酸根能氧化I-为I2,过量的I-与I2形成I3-,阳离子表面活性剂(CS)十四烷基二苄基氯化铵(TDMBA)、溴代十四烷基吡啶(TPB)、十六烷基三甲基溴化铵(CTMAB)、四丁基碘化铵(TBAI)等分别能与I3-形成缔合物微粒,且均在467 nm处产生共振散射效应。ClO2-浓度分别在0.00948~0.664μg/mL、0.0170~1.706μg/mL、0.0474~0.855μg/mL和0.0237~1.138μg/mL范围内与TDMBA、TPB、CTMAB及TBAI缔合微粒体系的共振强度成线性关系。据此建立了测定ClO2-的分析方法。各体系的检出限分别为0.00610μg/mL、0.00819μg/mL、0.0378μg/mL和0.00949μg/mL。其中TDMBA体系最稳定,且灵敏度也较高,用于水中ClO2-的测定,结果满意。     

离子色谱法测定水中的F-、Cl-、NO2--N、NO3--N、SO42-

应用DX－102型离子色谱仪测定水中的F^-、Cl^-、NO2^-－N、NO3^-－N及SO4^2-，淋洗液为1.42mmol/L NaHCO3-1.50mmol/L Na2CO3溶液，淋洗液流速为1.8mL/min，进样量为25μL。5种离子在上述实验条件下分离良好，定量测定的线性相关系数均在0.9995以上。     

离子色谱法同时测定蛋白胨中氯离子、硫酸根离子、碘离子

建立离子色谱法测定蛋白胨中氯离子、硫酸根离子、碘离子3种阴离子的含量。采用氢氧化钾淋洗液发生器产生的KOH溶液为流动相,进行梯度淋洗,流量为1.0 mL/min。氯离子、硫酸根离子的质量浓度分别在0.5～200μg/mL范围内与色谱峰面积呈良好的线性关系,碘离子的质量浓度在0.75～50μg/mL范围内与色谱峰面积呈良好的线性,线性相关系数均不小于0.999,检出限分别为0.003,0.01,0.22μg/mL。样品加标回收率为92.94%～96.59%,测定结果的相对标准偏差为2.42%～5.70%(n=9)。该方法灵敏、高效,可用于蛋白胨中氯离子、硫酸根离子、碘离子的快速准确测定。     

离子色谱同时分离测定三氟甲烷磺酸根,氟硼酸根及常见无机阴离子

建立了离子色谱-直接电导检测同时测定三氟甲烷磺酸根,氟硼酸根及常见无机阴离子(F-,Cl-,Br-,NO3-,SO24-)的方法。实验采用Shim-pack IC-A3阴离子交换色谱柱,分别选用对羟基苯甲酸-三(羟甲基)氨基甲烷-硼酸,邻苯二甲酸-三(羟甲基)氨基甲烷,邻苯二甲酸氢钾为淋洗液,考察了淋洗液种类,浓度及色谱柱温度对分离测定三氟甲烷磺酸根,氟硼酸根及常见无机阴离子的影响。最佳色谱条件为:以1.2mmol/L邻苯二甲酸氢钾为淋洗液,柱温30℃,流速1.0mL/min。在此条件下,可同时基线分离7种阴离子,且色谱峰形对称。所测阴离子的检出限(S/N=3)为0.02～1.88mg/L,保留时间和峰面积的相对标准偏差(n=5)分别小于0.17%和2.05%。应用本方法测定离子液体中三氟甲烷磺酸根,氟硼酸根及常见无机阴离子,加标回收率在97.0%～102.8%之间。本方法简单,准确,可靠,具有较好的实用性。     

串联电导及紫外检测器-离子色谱法测定土壤中6种有机酸根和无机阴离子

应用离子色谱法测定土壤样品中正丁酸根、草酸根、溴离子、碘离子、氯离子及硫酸根等6种有机酸根和无机阴离子的含量。样品(10.00g)用50mmol·L-1氢氧化钠溶液50mL超声提取60min,离心分离。取上清液,经0.22μm滤膜过滤和OnGuardⅡP柱净化。流出液稀释5倍后通过IonPac AG18柱分离,用不同浓度的氢氧化钾溶液进行梯度淋洗,用串联的电导检测器和紫外检测器(236nm)进行检测。前者用于除碘离子外的5种阴离子的测定,后者用于碘离子的测定。上述6种阴离子的峰面积分别在一定范围与其质量浓度呈线性关系,其检出限(3S/N)在0.013~0.095μg·g-1之间。加标回收率在92.0%~112%之间,测定值的相对标准偏差(n=6)在1.2%~7.2%之间。     

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.     

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.     

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.     

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.     

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.     

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.     

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.