干法消解–氢化物发生原子荧光光谱法测定颗粒饲料中的铅

建立了干法消解–氢化物发生原子荧光光谱法测定颗粒饲料中铅含量的方法。优化的实验条件:铁氰化钾含量为0.4%,草酸含量为0.04%,硼氢化钠–氢氧化钠溶液含量为2.0%,盐酸溶液(1∶1)的加入量为0.8 m L。铅的质量浓度在10~140μg/L范围内与荧光强度线性关系良好,相关系数(r2)为0.999 7,方法检出限为4.2μg/kg,测定结果的相对标准偏差为1.06%~1.87%(n=10),加标回收率为95.6%~98.9%。该方法测定结果准确,灵敏度高,可用于颗粒饲料中铅含量的检测。     

蒸发光散射高效液相色谱法测定黄芪饮片中的黄芪甲苷含量

采用蒸发光散射高效液相色谱法测定黄芪饮片中黄芪甲苷的含量。黄芪饮片分别用甲醇和正丁醇提取,以Na OH溶液洗涤,蒸干,再用甲醇溶解,采用Agilent SB–C18柱(250 mm×4.6 mm,5μm)分离测定,流动相为乙腈–水(32∶68),流量为1.0 m L/min,漂移管温度为80℃。方法检出限为1.5μg/m L,黄芪甲苷溶液的质量浓度在2~12μg/m L范围内与色谱峰面积线性关系良好(r2=0.999 6),测定结果的相对标准偏差为0.65%(n=6),平均加标回收率为99.6%。该方法稳定可靠,可用于黄芪药材及其生物制品中黄芪甲苷含量的测定。     

硫脲络合-火焰原子吸收光谱法测定古炉渣中的银、镉、钴、镍

建立硫脲络合–火焰原子吸收光谱法测定古炉渣中的银、镉、钴、镍。样品采用盐酸–硝酸–氢氟酸–高氯酸四酸体系溶解并蒸发至白烟冒尽,用体积分数10%的盐酸溶液溶解残渣至溶液清亮,加入10 mL 50 g/L硫脲溶液进行络合,定容于100 mL容量瓶中,混匀澄清后直接测定溶液中的银、镉、钴、镍。试验优化了灯电流、狭缝、乙炔流量和燃烧器高度等仪器工作条件,探讨了试样溶液的酸度、络合剂硫脲的浓度、共存元素对测定结果的影响。各元素校准曲线的线性相关系数均大于0.999 0,检出限为0.018～0.031μg/mL,加标回收率为97%～103%,样品测定结果的相对标准偏差为0.7%～1.8%(n=9)。该方法简便快捷,易于掌握,适合古炉渣样品的快速测定。     

气相色谱-质谱法测定猪肉中盐酸克伦特罗残留量

按NY/T 468-2006所述方法在碱性条件下,用乙酸乙酯提取和用盐酸溶液反萃取制得含有盐酸克伦特罗的试样溶液,调节溶液的酸度至pH 4.5后,经SCX固相萃取柱净化。在经净化后的试液中加入1.6mg·L-1美托洛尔溶液40μL作为内标。将溶液置于60℃水浴中吹氮蒸干,加入甲苯200μL和BSTFA衍生试剂100μL,于80℃烘箱中衍生1h。冷却后再加甲苯200μL,经DB-5MS毛细管柱分离,在SIM模式下进行MS测定,选择监测离子为m/z86(定量离子)和m/z262,243,187(定性离子)。内标法定量。盐酸克伦特罗的线性范围为16~512μg·L-1,其检出限(3S/N)为1.0μg·kg-1。以空白样品为基体进行加标回收试验,测得回收率在79.7%~86.6%之间,测定值的相对标准偏差(n=6)在4.8%~6.7%之间。     

二维离子色谱法测定海水中的铵离子

研究了二维离子色谱测定海水中铵离子的方法。海水样品经10倍稀释,一维色谱采用高容量的CS–165 mm柱,以30 mmol/L甲磺酸溶液等度淋洗,流量为1 m L/min,进样25μL,CSRS–300 4 mm抑制电导分离Na+,NH4+;二维色谱采用CS–12A 4 mm柱,以8 mmol/L甲磺酸溶液等度淋洗,流量为1 m L/min,以1 300μL定量环进样,SC–CSRS–300盐转换器抑制电导检测NH4+。结果表明:色谱峰面积与NH4+质量浓度线性相关,相关系数为0.999 9。10μg/L标准溶液测定结果的相对标准偏差为2.7%(n=7),NH4+的方法检出限和仪器检出限分别为0.42,0.05μg/L,海水中NH4+加标回收率为80.8%~105.8%。     

高效液相色谱-原子荧光光谱法测定化妆品中的无机汞、甲基汞、乙基汞

建立高效液相色谱–原子荧光光谱法对化妆品中无机汞、甲基汞、乙基汞进行测定。优化后的实验条件:负高压为300 V,灯电流为50 mA,炉温为200℃,还原剂为20 g/L硼氢化钾–5 g/L氢氧化钠溶液,流动相为5%甲醇–60 mmol/L乙酸铵–0.1%L-半胱氨酸溶液,载液为10%的盐酸。结果表明,无机汞、甲基汞、乙基汞的质量浓度在0～10μg/L范围内与色谱峰面积呈良好的线性关系,相关系数分别为0.999 7,0.998 3,0.999 3,方法的检出限均为0.067 mg/kg。测定结果的相对标准偏差为3.6%～4.8%(n=6),样品加标回收率为80.0%～97.3%。该方法快速、准确,灵敏度高,检测成本低,适用于化妆品中无机汞、甲基汞、乙基汞的测定。     

氯化亚锡还原-原子荧光光谱法测定银精矿中汞

建立了原子荧光光谱法测定银精矿中汞的分析方法。试样经盐酸、硝酸溶解,在盐酸介质中,以盐酸(5%)为载流,氯化亚锡(200g/L)溶液为还原剂,用原子荧光光谱法测定银精矿样品中汞的含量。对仪器的最佳工作条件、还原剂的种类和浓度、样品溶样方式、共存元素的干扰等各方面进行了详细研究。结果表明,方法的相对标准偏差为3.1%~9.1%,与冷原子吸收光谱法测定结果相吻合。方法的准确度和精密度均能满足银精矿样品的检测需求,值得推广使用。     

顶空毛细管气相色谱法测定吡虫啉中的丁酮

采用顶空毛细管气相色谱法测定吡虫啉中的丁酮残留量。样品经二氯甲烷溶解,用HP–5毛细管色谱柱分离,氢火焰离子化检测器检测,顶空平衡温度为70℃,平衡时间为10 min,以外标法计算含量。丁酮的质量浓度在2.0~510.0μg/m L范围内线性关系良好,相关系数r=0.999 7,方法的检出限为0.5μg/m L,样品3个水平的加标回收率为99.4%~102.1%,测定结果的相对标准偏差小于3.0%(n=5)。该方法简便快速,准确可靠,可用于吡虫啉产品的质量控制。     

固相萃取–气相色谱–质谱法测定地表水中的三氯苯

建立固相萃取–气相色谱–质谱联用法测定地表水中三氯苯的方法,对固相萃取柱、洗脱剂、甲醇用量进行优化试验。在200 m L水样中加入20 m L甲醇,采用C18固相萃取柱,以正己烷为洗脱溶剂萃取水中的三氯苯,用气相色谱–质谱法测定。结果表明,三氯苯的三种同分异构体分离良好,1,2,3-三氯苯、1,2,4-三氯苯、1,3,5-三氯苯的质量浓度在2.0~100μg/L范围内与其色谱峰面积均呈良好的线性,线性相关系数分别为0.999 1,0.999 4,0.999 2,检出限分别为0.004,0.005,0.005μg/L,加标回收率为90.3%~96.5%,测定结果的相对标准偏差均小于2%(n=7)。该方法操作简便、快速,定性定量准确,有机试剂用量少,适用于地表水中三氯苯的检测。     

石墨炉原子吸收光谱法直接测定铁镍基高温合金中的锡

建立石墨炉原子吸收光谱法直接测定铁镍基高温合金中的锡元素。通过研究基体效应、溶样酸、基体改进剂、灰化温度、原子化温度以及不同激发光源类型,确定最佳测定方案:用2 m L盐酸和0.4 m L硝酸溶解合金样品,灰化温度为1 200℃,原子化温度为2 200℃,选用0.003 mg Pd(NO_3)_2和0.03 mg NH_4H_2PO_4作为基体改进剂。在空心阴极灯(HCL)和无极放电灯(EDL)两光源条件下,标准工作曲线的线性相关系数均大于0.999,分别对GBW 01632和GBW 01634的测定结果与认可值进行t检验(α=0.05),均无显著性差异,短期稳定性好(RSD5.0%,n=8),锡的检出限分别为0.82μg/L(HCL)和0.75μg/L(EDL)。该方法无需萃取或其它复杂的前处理过程,测定结果准确、可靠,可实现铁镍基合金样品中锡的直接测定。     

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.     

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.     

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.