ICP-MS法测定土壤中稀土元素的消解条件研究

本文采用"硝酸-氢氟酸-高氯酸-硫酸"的湿法消解体系,优化了各种酸的用量和消解条件,以103Rh、185Re为内标元素,采用He碰撞模式消除多原子离子对待测元素的干扰,建立了土壤中15种稀土元素ICP-MS检测的湿法消解及分析方法。在优化条件下,不同类型国家土壤标准样品中15种稀土元素的检测结果的回收率为82.3%～113%,相对标准偏差为1.5%～8.7%,方法检出限0.001～0.015mg·kg~(-1),方法测定下限0.004～0.060mg·kg~(-1),此方法可用于多种类型土壤中稀土元素的ICP-MS检测,具有普遍适用性。     

微波酸溶-电感耦合等离子体质谱测定土壤和沉积物中Be~(2+)

建立了微波酸溶电感耦合等离子体质谱(ICP-MS)测定土壤和沉积物中Be2+的分析方法。采用HNO_3-HCl-HF混酸体系微波消解土壤及沉积物样品,以电热板赶酸的方法对样品进行前处理。优化了仪器参数,采用在线内标法消除基体效应。方法的检出限为0.0029mg/kg。对土壤标准样品进行测定,结果都在标准值范围之内;对土壤及沉积物实际样品进行测定,相对标准偏差均小于5%,加标回收率分别在94.4%~115%和91.5%~113%范围之内。实验结果表明,建立的ICP-MS法与石墨炉原子吸收(GFAA)法对土壤的沉积物中Be~(2+)的测定无差异性。     

电感耦合等离子体质谱(ICP-MS)法测定金绿宝石中16种痕量稀土元素

金绿宝石结构稳定,常规敞开酸溶、密闭酸溶、微波消解三种前处理方法并不能将其完全分解,测定结果偏低。本文采用碳酸钠-硼酸混合熔剂进行熔融,样品分解完全,建立了电感耦合等离子体质谱法(ICP-MS)测定金绿宝石中16种痕量稀土元素的分析方法。选择丰度高、干扰小的同位素、动能歧视碰撞池(KED)模式及干扰系数校正法消除质谱干扰,以185Re为内标元素及样品稀释降低基体干扰。实验表明：各稀土元素的校准曲线相关系数r值在0.9991~0.9998之间,方法检出限为0.0001~0.0134 μg/g,定量限为0.0005~0.0670 μg/g。采用国家标准物质GBW07151验证方法的精密度,计算出相对标准偏差(RSD, n=7)在1.3%~4.6%之间,并将此方法用于金绿宝石实际样品中稀土元素的测定,RSD为0.9%~3.2%,加标回收率为94%~104%,符合国家地质矿产行业标准,结果稳定、可靠。     

电感耦合等离子体质谱法测定高岭土中的15种稀土元素北大核心CSCD

样品经硝酸-氢氟酸-硫酸三酸消解后,以103 Rh为内标,采用电感耦合等离子体质谱法测定高岭土中的15种稀土元素。采用标准物质制备工作溶液绘制校正工作曲线消除质谱干扰,通过控制样品的稀释因子消除非质谱干扰。各元素的线性范围为0.20~200mg·kg^(-1),检出限在0.03~0.09 mg·kg^(-1)之间。方法用于分析岩石标准物质,测定值与认定值的相对误差在-6.7%~8.3%之间,相对标准偏差(n=5)在0.70%~5.9%之间。实际样品中15种稀土元素的测定值的相对标准偏差在3.8%~12%之间。     

微波消解-电感耦合等离子体质谱法(ICP-MS)同时测定土壤中11种金属元素

称取0.25 g样品加入5ml硝酸和2ml氢氟酸,用微波消解技术对样品进行前处理。以Re作为As、Pb、Tl的内标,Rh作为Cd、Co、Cr、Ni的内标,Bi作为Be、Cu、Zn的内标,Tb作为V的内标,建立了KED模式下可同时测定土壤中Be、As、Cd、Co、Cr、Cu、Ni、Pb、Tl、V、Zn 11种金属元素的微波消解ICP-MS方法。该方法线性关系良好,线性相关系数均在0.9990以上,检出限为0.002mg/kg-0.054 mg/kg。检测土壤标准物质GSS-17、GSS-18验证方法准确性,结果显示测定值均在标准差允许范围内,相对标准偏差在0.29%-5.33%,是一种快速、可靠的土壤多种金属元素检测方法。     

电感耦合等离子体质谱法测定高岭土中的15种稀土元素

样品经硝酸-氢氟酸-硫酸三酸消解后,以103 Rh为内标,采用电感耦合等离子体质谱法测定高岭土中的15种稀土元素。采用标准物质制备工作溶液绘制校正工作曲线消除质谱干扰,通过控制样品的稀释因子消除非质谱干扰。各元素的线性范围为0.20~200mg·kg~(-1),检出限在0.03~0.09 mg·kg~(-1)之间。方法用于分析岩石标准物质,测定值与认定值的相对误差在-6.7%~8.3%之间,相对标准偏差(n=5)在0.70%~5.9%之间。实际样品中15种稀土元素的测定值的相对标准偏差在3.8%~12%之间。     

微波消解-电感耦合等离子体质谱(ICP-MS)法同时测定土壤中11种金属元素

称取0.25g样品加入5mL硝酸和2mL氢氟酸,用微波消解技术对样品进行前处理。以Re作为As、Pb、Tl的内标,Rh作为Cd、Co、Cr、Ni的内标,Bi作为Be、Cu、Zn的内标,Tb作为V的内标,建立了KED模式下微波消解电感耦合等离子体质谱(ICP-MS)法同时测定土壤中Be、As、Cd、Co、Cr、Cu、Ni、Pb、Tl、V、Zn等11种金属元素的方法。方法线性关系良好,线性相关系数均在0.999以上,检出限为0.002～0.054mg/kg。检测土壤标准物质GSS-17、GSS-18验证方法准确性,结果显示测定值均在标准差允许范围内,相对标准偏差在0.29%～5.3%,是一种快速、可靠的土壤中多种金属元素同时检测方法。     

动能歧视(KED)-电感耦合等离子体质谱(ICP-MS)法测定贵州沉积型稀土矿中16种稀土元素

贵州沉积型稀土矿主要含有高岭土-锐钛矿石等矿物,存在高含量Si、Al、Fe、Ti、Zr等难溶基体元素,采用高压密闭微波消解法处理难以将其完全溶解,易使测定结果偏低,需再次消解或进一步电热板敞开酸溶处理,方法耗时长,不利于大批量样品检测需求。同时电感耦合等离子体质谱法(ICP-MS)在测定稀土元素时存在基体效应和质谱干扰,影响了检测数据的准确性。本文采用过氧化钠熔融分解样品,熔融物冷却后引入三乙醇胺溶液,在碱性溶液中,大量基体元素与三乙醇胺形成稳定配合物,并与大量溶剂钠盐存于溶液中,稀土元素与Ca、Mg、Sr、Ba等留存于沉淀,经过滤,实现稀土元素与大量基体元素分离,随后沉淀用(1+1)硝酸复溶,并以103Rh和185Re为在线注入内标协同降低基体干扰;启用动能歧视(KED)模式以降低测定过程中潜在的质谱干扰。实验结果表明:高压密闭微波消解法消解液浑浊有残渣,溶矿耗时长,测试结果偏低,碱溶法酸化后溶液清亮透明,稀土元素测定值准确性高;经条件试验,采用10%三乙醇胺溶液提取能较大降低基体干扰;启用KED模式可降低测定过程中的质谱干扰,且准确度优于STD模式;碱溶法方法检出限为0.008μg/g~0.049μg/g,测定下限为0.034μg/g~0.195μg/g,相对标准偏差RSD在0.78%～10.2%之间,相对误差RE在0.0225%~13.5%之间。经实际样品验证,碱熔法较适用于贵州沉积性稀土矿中16种稀土元素的测定。     

磷酸加王水复溶-电感耦合等离子体质谱（ICP-MS）法测定土壤样品中的20种金属元素

先用磷酸溶解样品,后加入王水复溶,可同时测定锂、铍、钪、钒、铬、钴、镍、铜、锌、锗、钼、镉、钡、镧、铈、钨、铊、铅、钍和铀元素。研究了消解体系、ICP-MS的最佳测量模式和最佳工作状态,并以铑为内标校正仪器的漂移。通过选择高、中、低几个国家一级水系沉积物和土壤标准物质随同样品一起溶解建立标准曲线,消除消解、分取和定容时带来的不确定误差和基体干扰,选择8个土壤标准物质为实验样本。最终结果表明,方法准确度(Δlgc)小于0.1,精密度(RSD)小于8%,方法满足测定要求,适用于地质普通样品的多金属检测。     

电感耦合等离子体质谱法测定固体生物质燃料中重金属

为开展重金属监测及环境保护,本文建立了电感耦合等离子体质谱法测定固体生物质燃料中重金属方法。对样品全消解酸溶法进行了实验研究,确定了微波消解酸体系和微波消解程序。采用Ge和In作为内标元素消除仪器干扰,方法线性关系良好,线性系数>0.999,检出限为0.001～0.089mg/kg。采用标准物质对方法准确性和稳定性进行验证,各元素测定值均在标准证书值范围内,相对标准偏差在0.36%～3.96%,Hg的加标平均回收率为104.7%。通过3家实验室协同实验验证了方法准确性,并给出了方法精密度。     

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.     

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%).     

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.     

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.