改性介孔二氧化硅分离富集-火焰原子吸收光谱法检测痕量镉

利用叠氮化介孔二氧化硅与炔丙胺反应,制备了炔丙胺介孔二氧化硅吸附材料,采用傅立叶红外光谱仪对其进行表征,并用于水样中痕量镉的富集。吸附材料在溶液pH 7.5时,恒温振荡30 min能高效吸附痕量Cd~(2+),吸附的Cd~(2+)用1 m L 1 mol/L HNO_3振荡30 min完全洗脱,火焰原子吸收法测定。在最佳实验条件下,方法的线性范围为0.5~50 ng/m L,方法检出限为0.06 ng/m L(3σ,n=20),富集倍数可达50倍,对20 ng/m L Cd~(2+)测定相对标准偏差为1.9%(n=20),加标回收率为95.5%~97.5%。吸附材料可循环使用25次以上并用于水样中Cd~(2+)的测定。     

印迹壳聚糖/凹土分离富集-FAAS测定水中痕量镉

建立了用离子印迹壳聚糖/凹土(ⅡGA)分离富集-火焰原子吸收光谱(FAAS)测定痕量镉的新方法.在动态吸附条件下,系统地研究了溶液pH值、流速、洗脱条件和干扰离子对痕量镉分离富集的影响;在pH4.5、上样流速为0.60 mL/min的条件下,镉能被ⅡCA定量富集;吸附的镉可用1.0 mol/L HCl-0.1 mol/...     

分子印迹功能介孔材料富集-火焰原子吸收光谱法测定溶液中痕量铅

以2-巯基苯骈噻唑为修饰剂,铅离子为印迹离子成功制备分子印迹功能介孔材料,并用扫描电镜(SEM)、傅里叶红外光谱对材料进行了结构表征。铅离子分子印迹功能介孔材料能很好地将Pb(II)与性质相近的二价重金属离子Cu(II),Cd(II)和Hg(II)分离,具有非常好的吸附选择性,且静态吸附容量0.64 mmol/g。利用该材料制备的分离富集柱可以很好地富集溶液中痕量铅离子,且仅用2 mL 0.5 mol/L EDTA以0.4 mL/min流速即可完全洗脱,富集倍数高达250倍。样品预富集后的火焰原子吸收光度法线性范围为0.5～1.2×104μg/L,r=0.999 2,检出限(3σ,n=11)为0.04μg/L。利用功能介孔材料分离富集水样中痕量铅离子,用火焰原子吸收法测定含量,相对标准偏差(RSD)小于等于3%(n=6),回收率在98.2%～99.1%之间。     

介孔TiO2分离富集-火焰原子吸收法测定矿样中痕量Cd(Ⅱ)

研究了介孔Ti O2分离富集材料的制备及其对Cd(Ⅱ)的吸附性能,考察了影响吸附和解吸的主要因素。pH=6.0时,介孔Ti O2能定量吸附溶液中的痕量Cd(Ⅱ),其静态饱和吸附容量为57.8 mg/g。吸附在介孔Ti O2上的Cd(Ⅱ)可用1 mol/L HCl洗脱,洗脱液中的Cd(Ⅱ)用火焰原子吸收法测定。本法对Cd(Ⅱ)的检出限(3σ)为23.3 ng/mL,相对标准偏差(RSD)为2.0%(n=7,c=1.0μg/mL),回收率在94.0%～102.5%之间。该方法用于矿样中痕量Cd(Ⅱ)的测定,结果满意。     

中孔分子筛P123-SH分离富集-火焰原子吸收法测定水样中镉

利用自制的中孔分子筛P123-SH作为镉的分离富集新材料,探讨了中孔分子筛P123-SH吸附镉的原理,优化了测定镉最佳条件。在pH6.5,室温下恒温振荡15min,镉可被该材料定量吸附,其静态吸附容量为9.52mg/g。吸附的镉可用2mol/LHCl洗脱,用火焰原子吸收法测定洗脱下来的镉。该方法线性范围为0.80～120μg/L;检出限为0.12μg/L,对50μg/LCd2 溶液平行测定7次,RSD=2.1%。此法已成功地应用于环境水样中痕量镉的测定。     

介孔Al2O3分离富集-火焰原子吸收法测定麻黄和马钱子中的铅

研究了介孔Al2O3分离富集-火焰原子吸收法测定麻黄和马钱子中的铅的新方法.探讨了溶液pH、吸附温度、洗脱条件及共存离子对铅分离富集的影响.在最佳实验条件下,介孔Al2O3能定量、快速吸附试液中的痕量pb2+,其静态饱和吸附容量为8.53 mg/g.吸附在介孔Al2O3上的pb2可用0.2 mol/LEDTA完全洗脱....     

离子印迹壳聚糖/凹土分离富集-火焰原子吸收光谱测定中药材中痕量Cd(Ⅱ)的研究

建立了离子印迹壳聚糖/凹凸棒石(IICA)分离富集-火焰原子吸收光谱(FAAS)测定中药材中痕量Cd(Ⅱ)的新方法。在动态吸附条件下,系统研究了溶液pH值、流速、洗脱条件和干扰离子对痕量Cd(Ⅱ)分离富集的影响。研究表明,在pH为4.5,上样流速为0.60mL/min条件下,Cd(Ⅱ)能被IICA定量富集;吸附的Cd(Ⅱ)可用1.0mol/L HCl-0.1mol/L甲基异丁酮的乙醇溶液,在流速为0.96mL/min条件下完全洗脱。优化条件下,IICA对Cd(Ⅱ)的动态吸附容量为56.45mg/g。线性范围为0.00097～1.28mg/L,r=0.9994,检出限(3σ,n=11)为0.97μg/L,相对标准偏差为1.32%(n=6,c=0.08mg/L),回收率在96.5%～106.4%之间。该方法操作简便,灵敏度和精密度高,可应用于实际中药材样品中痕量镉的测定。     

键合4-(2-吡啶偶氮)-间苯二酚螯合树脂分离富集-火焰原子吸收法测定蔬菜中痕量镉(Ⅱ)

本文合成了Amberlite XAD-4键合4-(2-吡啶偶氮)-间苯二酚螯合树脂,并考察了其对痕量镉(Ⅱ)的吸附性能。探讨了溶液pH、洗脱剂和干扰离子等对镉(Ⅱ)分离富集的影响。树脂吸附容量为4.7mg/g,吸附的镉(Ⅱ)用5mL 2mol/L HNO3乙醇溶液洗脱,火焰原子吸收法测定。在最佳实验条件下,回收率为94.4%～97.9%,相对标准偏差在1.7%～2.7%之间。方法可用于蔬菜中镉(Ⅱ)的测定。     

有机-无机介孔材料对痕量汞的吸附性能的研究

研究了一种有机-无机介孔材料在分离富集和测定痕量汞中的应用,探讨了溶液pH、温度、洗脱条件及干扰离子对汞分离富集的影响,结果发现该材料对Hg的吸附具有较高的选择性和较大的吸附容量。在pH 3.2、温度为20±1℃条件下,汞可被该材料定量吸附。其静态饱和吸附容量为119.15 mg/g。吸附的汞可用浓HCl洗脱,用原子荧光法测定洗脱下来的汞。该方法测定汞的检出限达1.89×10-9g/L(3σ),相对标准偏差为2.7%(n=11,ρ=0.5 ng/mL),线性范围为0.005~5 ng/mL,加标回收率95.3%~104.5%。此法已应用于环境水样中痕量汞的测定。     

中孔分子筛SBA-15-NH2 分离富集火焰原子吸收光谱法测定烟花中痕量钯的研究与应用

建立了中孔分子筛SBA-15-NH2分离富集火焰原子吸收光谱法测定痕量钯的新方法,探讨了中孔分子筛SBA-15-NH2材料吸附钯的原理和最佳条件.在pH 3.0、温度为(15±1) ℃的条件下,钯可被该材料定量吸附,其吸附容量为1.21 mg/g.吸附的钯用饱和硫脲溶液洗脱,并用火焰原子吸收法测定洗脱的钯.该方法测定钯的检出限为0.59 μg/L(3σ,n=11),线性范围为0.002 ～1.2 mg/L,加标回收率为98% ～107%.对0.05 mg/L的Pd2+溶液平行测定7次,RSD为2.24%.方法用于烟花中痕量钯的测定,结果满意.     

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.     

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.     

A carbanion induced synthesis of highly congested pyrazole and imidazole containing heterocycles

An efficient approach to the synthesis of highly congested di, penta and hexacyclic pyrazoles as well as imidazole fragment containing novel heterocyclic molecule has been developed through a carbanion induced transformation of suitably functionalized 2H-pyran-2-ones, benzo[h]chromene and thiochromeno[4,3-b]pyrans. Due to the presence of fluorescence, we report their prime application metal sensor as off/on switching in ferric ions.     

Synthesis of pyrrolo[1,2-a]pyrazines and pyrazino[1,2-a]indoles by Curtius reaction in Morita-Baylis-Hillman derivatives

Synthesis of substituted pyrrolo[1,2-a]pyrazines and pyrazino[1,2-a]indoles from the Morita-Baylis-Hillman derivatives of acrylates via saponification followed by Curtius reaction is described.     

Selective synthesis of 4,5-dihydroimidazo- and imidazo[1,5-a]quinoxalines via modified Pictet–Spengler reaction

An efficient tandem approach for the selective synthesis of 4,5-dihydroimidazo[1,5-a]quinoxalines 6a–g and imidazo[1,5-a]quinoxalines 7a–h by the reaction of 2-imidazolyl anilines 4a–c with aryl aldehydes 5a–k under mild reaction conditions is described. Introduction of electron releasing alkyl groups in substrates 4a–b was found to be instrumental for the success of the reaction.     

Understanding the Diels-Alder reactivity of 1,2-azaborine analogues

The Diels-Alder reactivity of 1,2-heteroborines (H₄C₄B(H)X, X?=?NH, PH, AsH; O, S, Se) has been computationally explored by means of Density Functional Theory (DFT) calculations. The influence of the HB?=?X fragment on the reactivity of the system has been quantitatively analyzed in detail by means of the so-called Activation Strain Model (ASM) of reactivity. It is found that the interaction between these species and the dienophile is significantly stronger than that computed for their all-carbon isoelectronic counterpart, benzene. In addition, the strain energy plays a key role in the observed reactivity trends. The role of the aromaticity strength of these heteroarenes on the reactivity is also assessed.