阀切换-离子色谱法测定高纯硼酸中的痕量阴离子

研究了高纯硼酸中痕量阴离子的离子色谱测定方法.建立了使用阈切换技术联合离子色谱同时测定高纯硼酸中痕量阴离子的检测方法.样品经水溶解后,通过阀切换技术,使用蠕动泵和IonPac TAC-ULPI超低压浓缩柱,消除基体中硼酸根的干扰,同时在线富集样品中的阴离子,最后使用IonPac AS15分析柱进行分离.在20～500μg/L浓度范围内,7种常见阴离子的工作曲线的线性相关系数r均优于0.995,对硼酸样品进行加标,7种阴离子的平均回收率为90%～106%.该方法可应用于高纯硼酸中痕量阴离子的检测.     

超高含量氯离子基体下痕量亚硝酸盐的检测

介绍了一种无需对样品进行除氯处理,采用全新的离子色谱柱,抑制型电导离子色谱法检测,测定超高Cl-基体下痕量亚硝酸盐及其它常见阴离子的方法.其中Cl-浓度与亚硝酸盐浓度比可达到50000:1甚至100000:1,实现良好分离.选择色谱条件为:IonPac AS23阴离子交换柱,手工配制碳酸盐淋洗液等度淋洗,抑制型电导检测.污水样品通过Dionex OnGuardⅡRP柱和0.22 μm微孔尼龙膜处理.该方法采用25 μL进样,8种常见阴离子的检出限为0.2～5.8μg/L,线性范围均超过2个数量级,相关系数r在0.9996～0.9999的范围内,连续11次进样检出所有阴离子的RSD均小于5%,加标回收率结果在93%～106%之间.该方法具有选择性好,灵敏度高,操作简单等特点,从根本上解决了高氯离子基体中痕量亚硝酸盐及其它常见阴离子检测的问题,用于实际污水样品的检测.     

柠檬酸试剂中痕量无机阴阳离子的离子色谱法测定

选用柱容量较高、亲水性较强的阴离子分析柱IonPac AS18,以30mmol／L KOH为淋洗液,等度淋洗分析了高浓度柠檬酸中的痕量无机阴离子。选用柱容量较高的阳离子分析柱IonPac CS12A,以H2SO4作淋洗液分析了柠檬酸试剂中的痕量阳离子。在所选色谱条件下,无需样品前处理,直接进样,电导检测,高浓度柠檬酸不影响痕量阴离子或阳离子的测定。方法具有良好的线性(r=0．9941～1．000),样品中所测离子峰面积的相对标准偏差(RSD)均在9．0％以下(n=7),回收率在82．7％～110％之间,检出限低于3．7μg/L。     

阀切换-离子色谱法测定分析纯硫酸钠中痕量氯离子

建立了阀切换-离子色谱法测定分析纯硫酸钠固体中痕量氯离子含量的方法。ICS-2100离子色谱系统,配置十通阀,用IonPac AS18色谱柱将硫酸钠固体样品中的氯离子和硫酸根离子预分离后,以IonPac TAC-ULP1为富集柱,将氯离子富集后在相同的IonPac AS18色谱柱上进行定量分析。同时以淋洗液发生器产生的不同浓度的KOH作为淋洗液,以抑制型电导检测器测定氯离子的含量。结果表明,阀切换-离子色谱法测定分析纯硫酸钠固体中的痕量氯离子,检出限为10 μg/L,线性相关系数(r2)大于0.999,实际样品的加标回收率为98.0%～103.0%,具有分离度和灵敏度高,选择性好,操作简单等特点。该方法能够准确测定硫酸钠固体中痕量氯离子的含量,适用于高纯化学试剂中痕量氯离子的分离测定。     

大体积直接进样离子色谱法测定饮用水中痕量溴酸盐

建立了一种无需样品前处理,直接大体积进样,电导检测饮用水中痕量溴酸盐的离子色谱新方法。分析柱为容量高、亲水性强的Dionex IonPac AS19阴离子交换柱,EG40在线产生KOH淋洗液,等浓度泵作梯度淋洗。该方法对溴酸盐的检出限为0．2μg／L;在1～100μg/L范围内具有良好的线性（r=0．9996）。将该方法用于北京市自来水和市售瓶装水样品中痕量溴酸盐的检测,实际样品的加标回收率在90％～106％之间;1μg／L溴酸盐连续进样10次,相对标准偏差（RSD）为5．7％。     

在线中和富集-离子色谱法测定高纯氢氧化钠中痕量阴离子

建立了在线中和、富集待测离子后用离子色谱对高纯氢氧化钠中痕量阴离子进行检测的分析方法。样品经超纯水溶解、稀释后直接进样。试样经外接纯水输送至In Guard H消除OH-基体干扰,然后经过富集柱浓缩待测阴离子,再经阀切换技术进入离子色谱系统,以淋洗液发生器产生的KOH为淋洗液,流速为1.0m L/min,采用Ion Pac AS11-HC分析柱分离后,电导检测器检测。结果表明,在0.1~10.0 mg/L的线性范围内,氯离子、硫酸根、氯酸根的线性相关系数分别为0.999 8,0.999 6和0.999 2。方法对于氯离子、硫酸根、氯酸根的检出限分别为0.03,0.07,0.06 mg/kg,加标回收率分别为92%~104%,91%~111%和92%~106%,相对标准偏差(n=7)均小于2.0%。     

在线基体消除-离子色谱法测定墨水染料中的氯及硫酸盐

建立了一种在线基体消除的方法,采用离子色谱法测定了墨水染料中的氯和硫酸盐。样品经溶解、稀释后直接进样,在纯水的输送下依次经过DIONEX OnGuard Ⅱ P和IonPac NG1柱,在线实现了墨水样品中染料和疏水性干扰基体的去除,死时间流出的待测阴离子浓缩于阴离子交换柱IonPac AG11-HC。浓缩柱经阀切换进入离子色谱系统,以4.5 mmol/L Na2CO3-0.8 mmol/L NaHCO3作为淋洗液,流速1.2 mL/min,待测离子经IonPac AS23（4 mm×250 mm）分析柱分离,采用DIONEX DS6电导检测器检测,外标法定量。Cl－和SO2-4的线性范围分别为0.05~5.0、0.1~10.0 mg/L,相关系数分别为0.999 8和 0.999 7,加标回收率为94%~103%,相对标准偏差（n=11）小于1.0%,检出限（S/N=3）分别为0.02、0.05 mg/L。该方法用于墨水染料中氯和硫酸盐的测定,结果满意。     

离子色谱法同时分析啤酒中的有机酸和无机阴离子

建立了以NaOH-甲醇混合淋洗液,离子交换色谱柱,电导检测器检测,分离啤酒中有机酸和无机阴离子的离子色谱法.结果表明：在20 min内分离出啤酒中的11种主要有机酸与无机阴离子,方法回收率和相对标准偏差分别为96.30%～104.8%和0.02%～4.0%.     

氧弹燃烧-离子色谱法测定海藻酸钠中的氯离子和硫酸根离子

采用氧弹燃烧法对海藻酸钠样品进行燃烧,用碳酸钠作为吸收液进行吸收,建立了离子色谱-抑制电导法检测海藻酸钠中阴离子的方法.实验采用SH-AC-1型离子交换色谱柱,最佳色谱条件:以3.6 mmol/L碳酸钠为淋洗液,柱温45℃,流速0.7 mL/min.在此条件下,可同时分离Cl-、SO42-离子,且色谱峰型对称,所测C1...     

高效阴离子交换色谱-电化学法测定酱油中的氨基酸

采用高效阴离子交换色谱-电化学检测器分离并测定了18种常见氨基酸. 实验首先对酱油样品进行了简单前处理, 然后以一定浓度的NaOH和NaAc溶液为淋洗液, 选择合适的梯度淋洗条件, 使18种氨基酸在阴离子交换色谱柱上实现良好地分离, 并用脉冲安培检测器进行了测定. 氨基酸的检出限为1.7～20.0 μg/L, 样品加标回收率在85%～108%范围内. 方法灵敏度高, 操作简单, 重现性好, 不需要繁琐的柱前或柱后衍生操作. 已应用到生抽和老抽酱油调味料产品中氨基酸的测定.     

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.     

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.     

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.     

N-Heterocyclic carbene-palladacyclic complexes: synthesis,characterization and their applications in the C-N coupling and α-arylation of ketones using aryl chlorides

N-Heterocyclic carbene-palladacyclic complexes 3 were successfully achieved in a one-pot procedure under mild conditions. The structure of 3a was unambiguously confirmed by X-ray single crystal diffraction and it was an active catalyst in the Buchwald-Hartwig amination and α-arylation of ketones even at very low catalyst loadings (0.01?mol%).     

Iodine-mediated oxidative Pictet-Spengler reaction using terminal alkyne as the 2-oxoaldehyde surrogate for the synthesis of 1-aroyl-β-carbolines and fused-nitrogen heterocycles

An efficient iodine-mediated oxidative Pictet-Spengler reaction in dimethyl sulphoxide (DMSO) using terminal alkynes as the 2-oxoaldehyde surrogate for the synthesis of aryl (9H-pyrido[3,4-b]indol-1-yl)methanones is described. The scope of the protocol includes the total synthesis of Fascaplysin, Eudistomins Y₁ and Y₂. The methodology is extended for preparing pyrrolo[1,2-a]-quinoxaline and indolo[1,5-a]quinoxaline derivatives. The utility of 1-aroyl-β-carbolines was demonstrated by performing palladium-catalyzed β-carboline directed ortho-C(sp2)-H functionalization of the phenyl ring with thiomethyl (SMe) group using DMSO as source and for accessing 4-aryl-canthin-6-ones.     

Facile synthesis of bicyclic 1-arylpyrazol-5-ones

In this Letter, we described a facile method for constructing fused bicyclic 1-arylpyrazol-5-one ring system. We employed various methylene-containing carboxylic acids as the substrates and proved that the pyrazolone ring closure requires activated methylene group in intermediate II. Accordingly, a series of structurally diversified, fused bicyclic 1-arylpyrazol-5-ones was prepared in moderate to high yields using the requisite substrates.