鱿鱼丝中砷的形态分析

采用电感耦合等离子体-质谱(ICP-MS)测定了14种鱿鱼丝(Dried Shredded Squid,DSS)中的砷总量,发现14种鱿鱼丝中的砷总量均低于2μg.g-1;用高效液相色谱(HPLC)与ICP-MS联用技术建立了As(Ⅲ)、As(Ⅴ)、二甲基胂酸(DMA)、甲基胂酸(MMA)、砷甜菜碱(AsB)和砷胆碱(AsC)六种砷形态的分离分析方法;采用快速溶剂萃取(ASE)、超声溶剂提取(SON)和盐酸浸提三种不同的前处理方法分析了3种鱿鱼丝中的砷形态,发现鱿鱼丝中的砷主要以AsB形式存在。     

高效液相色谱-电感耦合等离子体-串联质谱法同时测定饲料中As(Ⅲ)、As(Ⅴ)、氨苯胂酸和洛克沙胂

建立了饲料中As(Ⅲ)、As(Ⅴ)、氨苯胂酸(p-ASA)和洛克沙胂(ROX)不同形态砷的高效液相色谱-电感耦合等离子体-串联质谱(HPLC-ICP-MS/MS)检测方法。样品经甲醇-水(1∶1,V/V)超声提取,用Shiseido MGⅡC18色谱柱(250×4.6 mm,5μm)对4种砷形态进行分离,以pH=4.7的6mmol/L四丁基氢氧化铵(TBAH)-甲醇(92∶8,V/V)溶液及pH=1.9的0.05%三氟乙酸(TFA)-甲醇(92∶8,V/V)溶液为流动相进行梯度洗脱。然后通过电感耦合等离子体质谱进行监测,外标法定量。结果表明,在优化的实验条件下,各形态砷在0~50μg/L范围内线性良好(R≥0.9999),As(Ⅲ)、As(Ⅴ)、氨苯胂酸(p-ASA)和洛克沙胂(ROX)的检测限分别为0.05、0.10、0.08、0.60μg/L,4种形态砷的加标回收率范围在85.9%~104.6%之间,相对标准偏差(RSD)均小于5%。通过对实际样品的检测,该方法适用于饲料中常见形态砷的检测。     

液相色谱-氢化物发生原子荧光光谱法测定饲料中砷的形态

建立了饲料中亚砷酸盐(As~(3+))、砷酸盐(As~(5+))、一甲基砷酸(MMA)、二甲基砷酸(DMA)、对氨基苯胂酸(p-ASA)、羟基苯胂酸(4-OH)和洛克沙胂(ROX)共7种不同形态砷的高效液相色谱-氢化物发生原子荧光光谱(HPLC-HG-AFS)分析方法。饲料样品采用甲醇-水(1∶1,V/V)溶液提取,15 mmol/L(NH_4)_2HPO_4和10 mmol/L邻苯二甲酸氢钾为流动相,经PRP-X100阴离子交换色谱柱分离后,由HG-AFS测定。结果表明,7种砷形态标准曲线的线性关系良好(R2≥0.9964),方法检出限为5~30 μg/kg,平均回收率为76.3%~108.1%,日内相对标准偏差≤7.7%,日间相对标准偏差≤17.4%。本方法灵敏度高、前处理简单、运行费用低廉,适用于饲料产品中砷的形态分析。     

高效液相色谱-电感耦合等离子体质谱联用测定鸡肉及鸡肝中10种砷形态化合物

建立了一种有效分离检测鸡肉及鸡肝样品中洛克沙砷(ROX)、阿散酸(ASA)、硝苯胂酸(NPAA)、卡巴胂(CBS)、砷酸(AsⅤ)、亚砷酸(AsⅢ)、一甲基胂酸(MMA)、二甲基胂酸(DMA)、砷甜菜碱(As B)和砷胆碱(As C)共10种砷形态化合物的高效液相色谱-电感耦合等离子体质谱(HPLC-ICP-MS)分析方法。采用10%甲醇为提取液,碳酸铵溶液为流动相,以阴离子分析柱将样品提取液进行分离,最后进行ICP-MS测定。10种砷形态化合物在0.1~100μg/L范围内线性关系良好,相关系数(r2)均大于0.999,检出限为0.3~1.5μg/kg,定量下限为1.0~5.0μg/kg,加标回收率为81.3%~97.7%,相对标准偏差为0.1%~3.5%。该法重现性好、灵敏度高,且采用组织研磨仪机械振荡5 min即可成功提取10种砷形态化合物,与常规水浴加热振荡提取相比更加简便、高效。该法适用于鸡肉及鸡肝样品中10种砷形态化合物的同时检测,通过对实际样品的分析测定,在鸡肝样品中检出阿散酸和亚砷酸。     

离子色谱-电感耦合等离子体质谱法测定地下水中4种形态砷的含量

采用离子色谱-电感耦合等离子体质谱法(IC-ICP-MS)测定地下水中4种形态砷[As(Ⅲ)、As(Ⅳ)、一甲基胂酸、二甲基胂酸]的含量。水样在IonPac AS14阴离子色谱柱上分离,采用IonPac AG14阴离子保护柱,以碳酸氢铵为流动相进行梯度洗脱,4种砷形态在15min内完全分离。在进样量25μL时,4种形态砷的线性范围为0.50~200μg·L-1,检出限在0.03~0.06μg·L-1之间,加标回收率在97.0%~102%之间。此方法用于测定地下水样,测定结果与电感耦合等离子体质谱法的结果相吻合。     

高效液相色谱-电感耦合等离子体质谱法测定淡水中7种元素形态的含量

建立了高效液相色谱-电感耦合等离子体质谱法同时测定淡水中亚砷酸盐[As(Ⅲ)]、砷酸盐[As(Ⅴ)]、一甲基胂酸(MMA)、二甲基胂酸(DMA)、亚硒酸盐[Se(Ⅳ)]、硒酸盐[Se(Ⅵ)]和六价铬[Cr(Ⅵ)]的方法。采用以不同体积比的pH 8.7的20mmol·L-1硝酸铵溶液和pH 8.7的60mmol·L-1硝酸铵溶液为流动相进行梯度洗脱,通过优化的色谱条件实现了7种元素形态在14min完成色谱分离,氯化物对75 As、77 Se、53 Cr无干扰。7种元素形态在一定范围内呈线性,As(Ⅲ)、As(Ⅴ)、MMA、DMA、Se(Ⅳ)、Se(Ⅵ)和Cr(Ⅵ)的检出限(3S/N)分别为0.06,0.02,0.04,0.05,1.00,1.00,0.20μg·L-1。按标准加入法进行回收试验,回收率为80.1%~101%,相对标准偏差(n=6)为0.59%~5.2%。     

高效液相色谱-电感耦合等离子体串联质谱法同时测定土壤中的阿散酸、洛克沙胂及其降解产物

建立了高效液相色谱-电感耦合等离子体串联质谱(HPLC-ICP-MS/MS)同时测定土壤中阿散酸(p-ASA)、洛克沙胂(ROX)及其降解产物无机砷(i-As)(亚砷酸(As(Ⅲ))和砷酸(As(Ⅴ)))、一甲基砷(MMA)和二甲基砷(DMA)等5种砷形态的分析方法。以0.1 mol/L NaH_2PO_4-0.1 mol/L H_3PO_4(体积比9∶1)为提取剂,液固比为50 mL/g,样品经微波辅助提取(80℃,30 min)后,采用Hamilton PRP-X100阴离子交换柱(250 mm×4.1 mm,10μm),以60 mmol/L(NH_4)_2HPO_4-5%甲醇(pH 6.0)和水为流动相进行梯度洗脱,在15 min内实现了5种砷形态的良好分离。在优化条件下,各砷形态在0～500μg/L范围内线性良好(r~2≥0.999 1),检出限为0.043～0.080μg/kg(以As计),相对标准偏差为1.7%～3.8%。将该方法用于分析3种土壤样品,各砷形态的加标回收率为71.6%～106%。该方法简单、快速、准确、可靠,适用于土壤中阿散酸、洛克沙胂和常规砷形态的检测。     

高效液相色谱/氢化物发生-原子荧光光谱法检测微藻中的砷形态

建立了盐藻和螺旋藻中砷形态的高效液相色谱/氢化物发生-原子荧光光谱(HPLC/HG-AFS)分析方法。优化了微藻中砷形态的提取方法、流动相浓度及pH、KBH4浓度、载流浓度、AFS参数。优化后砷形态的提取效率范围为97.3%~99.1%,在优化后的实验条件下,As(Ⅲ)、二甲基砷酸(DMA)、一甲基砷酸(MMA)和As(Ⅴ)的线性相关系数分别为0.9999、0.9996、0.9997和0.9994,检出限分别为0.19、0.40、0.34、0.52μg/L,盐藻的砷加标回收率为91.5%~100.8%,螺旋藻的砷加标回收率为95.6%~104.5%。研究结果表明,该方法检测快速(10min),且测得微藻中的砷形态数据准确、可靠。     

方便面中砷元素的形态分析

建立了硝酸提取,高效液相色谱一原子荧光联用技术测定方便面中不同砷形态的分析方法。样品经0．15mol／L盐酸溶液超声提取后离心过滤,上机测试。实验表明：砷的4种形态亚砷酸[As（Ⅲ）]、砷酸[As（V）]、一甲基胂酸（MMA）和二甲基胂酸（DMA）的线性范围为0-50μg／L,相关系数（r）均优于0．9990,检出限在2～8μg／L之间,砷各形态的测量重复性（以RSD表示）均小于5％,样品的加标回收率为78％-118％。同时用原子荧光光度计检测了样品中总砷,并将两种方法测定结果进行了对比,结果符合理论以及文献报道。该方法操作简单快速、结果准确可靠,适用于方便面中砷形态的分析测定。     

HPLC-HG-AFS测定大气颗粒物中砷的形态

采用高效液相色谱-氢化物发生原子荧光光谱联用测定了北京大气颗粒物中As(III),As(Ⅴ),二甲基砷酸(DMA)和一甲基砷酸(MMA)的含量。研究了仪器条件、流动相组成和梯度洗脱程序对砷形态分离的影响。实验结果显示,在优化的色谱与氢化原子荧光检测条件下,采用pH6.0,浓度为10 mmol/L和200 mmol/L NH4H2PO4为流动相A和B,在1~3 min内用60%的A和40%的B洗脱使砷的4种形态达到最佳分离效。As(III),As(Ⅴ),DMA和MMA的检出限为1.45,1.22,1.91和1.64 mg/L,回收率为90.5%~93.2%,相对标准偏差为0.38%~1.7%。方法适用于大气颗粒物中砷的形态分析研究。     

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.