ICP-AES测定铀污染土壤植物中铀的研究

采用电感耦合等离子体发射光谱(ICP-AES)对铀污染土壤植物中铀的测定方法进行了研究.在λU385.958 nm处,选择了仪器的最佳工作条件,考察了酸度和常见共存元素对测定的干扰情况,并且对比了干灰化消解和湿式消解对测定的影响.研究发现2%硝酸溶液为最佳介质,干扰离子对测定没有显著影响,干灰化消解比湿式消解得彻底.在选定条件下,方法检出限为0.18 mg·L-1,测定下限为0.61 mg·L-1,5.0000 mg·L-1的铀标准溶液的相对标准偏差RSD(n=10)为0.81%,方法回收率为96.2%～106.2%.该方法操作简单,快速.结果表明,用ICP-AES测定铀污染土壤植物样品中的铀是可行的.     

电堆集-非水毛细管电泳分离测定甘草次酸和阿魏酸的研究

建立了电堆集富集-非水毛细管电泳(NACE)同时分离测定甘草中甘草酸和阿魏酸的新方法.系统研究了电压、非水溶剂、乙酸钠浓度、氢氧化钠浓度、样品溶剂等因素对电堆集和分离效果的影响,确立了分离和富集的最佳条件.以甲醇-乙腈(体积比4 : 6)为非水介质,30 mmol·L-1乙酸钠-2.5 mmol·L-1氢氧化钠为背景电解质;分离电压-20 kV,检测波长254 nm.在优化条件下,甘草次酸在0.80 ～12.80 mg·L-1(r＝0.999 6),阿魏酸在0.77 ～45.60 mg·L-1(r＝0.999 6)质量浓度范围内线性关系良好,回收率分别为97% ～102%,98% ～102%;甘草次酸检出限为0.069 mg·L-1,阿魏酸检出限为0.087 mg·L-1,RSD均不大于4.6%.     

测定食品及生物样品中微量锡的消化方法探讨

采用干灰化、硝酸-高氯酸、硝酸-硫酸-高氯酸和用硝酸过氧化氢微波消解4种消化方法消化样品,氢化物发生-原子荧光光谱法测定食品及生物样品中微量锡。方法线性范围为20.0μg.L-1以内,相关系数为0.999 8,经过比较,微波消解和硝酸-硫酸-高氯酸消解方法较理想,回收率分别为98.2%~101.4%和97.4%~102.8%,相对标准偏差分别为2.39%~3.85%和3.25%~3.82%。只测定锡时,微波消解和硝酸-硫酸-高氯酸消解法均可,但如锡与其他微量元素需要同时测定,为避免引入有干扰的硫酸根,以用硝酸-过氧化氢微波消解为好。     

纳氏试剂分光光度法测定土壤中全氮含量

提出了纳氏试剂分光光度法测定土壤中全氮含量。以硫酸铜为加速剂,用硫酸对土壤样品进行消解。消解完毕的溶液用400g·L-1氢氧化钠溶液调节其酸度至pH 10左右,溶液与沉淀一起移入容量瓶中,定容至200mL。移取上清液10mL于50mL比色管中,加入酒石酸钾钠溶液作掩蔽剂,加入纳氏试剂显色后,加水定容,于波长420nm处测量其吸光度并计算土壤样品中全氮含量。氮的质量浓度在2mg·L-1以内与吸光度呈线性关系。方法用于土壤样品分析,测定值与滴定法测定值相符,测定值的相对标准偏差(n=10)为0.24%;回收率在92.3%~112%之间。     

微波消解样品-火焰原子吸收光谱法测定美白化妆品中铅和铜

乳液和水类美白化妆品经硝酸-过氧化氢混合液消解,粉类美白化妆品经硝酸-过氧化氢-氢氟酸混合液消解,用火焰原子吸收光谱法测定样品中铅和铜的含量。在优化的仪器工作条件下,铅和铜的质量浓度分别在9.0 mg·L-1和11.0 mg·L-1以内与其吸光度呈线性关系,检出限(3s)分别为21.8μg·L-1和16.2μg·L-1。方法用于美白化妆品中铅、铜的测定,测得回收率分别在98.0%~102.5%和96.7%~105.0%之间。     

高效液相色谱法测定硫酸沙丁胺醇

利用高效液相色谱仪-电子捕获检测器(HPLC-ECD)测定了市售片剂硫酸沙丁胺醇的含量.结果表明,利用HPLC-ECD技术测定硫酸沙丁胺醇的线性范围为0.944~33.8mg·L-1(r=0.999 6);回收率为99.0%~107.8%(RSD≤4.6%).该法可用于测定片剂的硫酸沙丁胺含量.     

苯胺蓝-溴酸钾体系催化分光光度法测定水中痕量亚硝酸盐

在硫酸介质中,亚硝酸盐对溴酸钾氧化苯胺蓝褪色反应有明显的催化作用,据此提出了测定痕量亚硝酸盐催化分光光度方法。优化的试验条件如下:1 1.0mol·L-1硫酸溶液的用量为1.8mL;2 3×10-4 mol·L-1苯胺蓝溶液用量为1.5mL;3 0.02mol·L-1溴酸钾溶液用量为1.1mL;4反应温度为30℃。该方法的线性范围分别为0.01~0.2mg·L-1和0.2~1.0mg·L-1,检出限(3s/k)为4.6×10-6g·L-1。方法用于水样的分析,回收率在96.0%~104%之间,测定值的相对标准偏差(n=6)在1.6%~2.3%之间。     

SmartChem140全自动化学分析仪测定土壤全氮全磷的研究

本文以胶州湾湿地土壤为样品,建立了基于SmartChem140全自动化学分析仪,同时测定土壤全氮和全磷的方法。利用全自动化学分析仪可以同时快速、准确测定土壤中的全氮和全磷,全氮和全磷分别在0~6.0mg·L-1和0~5.0mg·L-1范围内线性良好,相关系数(R2)分别为0.9994、0.9995;测定结果与凯氏定氮法、磷钼蓝比色法对比无显著差异,相对误差均小于4%,相对标准偏差分别为1.39%和1.07%,样品的加标回收率分别在97.68%~102.12%和97.35%~101.88%之间。研究结果表明,该方法准确度高、稳定性好,回收率高,操作简便,测定结果能满足对土壤全氮、全磷的监测要求。     

磷铋钼蓝分光光度法测定水果、蔬菜及饮料中L-抗坏血酸

Bi~(3+)与Mo(Ⅵ)和PO_4~(3-)在硫酸介质中反应生成黄色的磷铋钼杂多酸,然后被L-抗坏血酸还原为磷铋钼蓝,据此建立了分光光度法测定水果、蔬菜及饮料中L-抗坏血酸的方法。优化的试验条件如下:(1)测定波长为710nm;(2)1.95×10~(-2) mol·L~(-1)磷酸二氢钾溶液的用量为3.0mL;(3)6.51×10~(-2) mol·L~(-1)钼酸铵溶液的用量为4.0 mL;(4)2.06×10~(-4) mol·L~(-1)硝酸铋溶液的用量为1mL;(5)硫酸的浓度为0.16mol·L~(-1);(6)反应温度为室温。L-抗坏血酸的质量浓度在4~120mg·L~(-1)内与其对应的吸光度呈线性关系,表观摩尔吸光率为3.59×10~3L·mol~(-1)·cm~(-1),检出限(3s/k)为0.2 mg·L~(-1)。方法用于水果、蔬菜及饮料样品的分析,加标回收率为98.0%~102%,测定值的相对标准偏差(n=11)为1.1%~2.3%。     

四酸微波消解-电感耦合等离子体原子发射光谱法测定土壤中6种重金属元素

建立了四酸微波消解-电感耦合等离子体原子发射光谱法(ICP-AES)测定土壤中6种重金属元素的方法。取0.10～0.20 g土壤样品用少量水润湿,加入6 mL硝酸、2 mL盐酸、1 mL氢氟酸和1 mL 30%(质量分数,下同)过氧化氢溶液,静置15 min使其充分反应,置于微波消解仪中按升温程序消解。消解液置于电热板上以140℃加热至溶液近干,用1%(体积分数)硝酸溶液溶解残渣并将其定容至25 mL,按优化的ICP-AES条件分析。所选的Pb、As、Ni、Cu、Zn、Cr的分析谱线分别为220.353,189.042,231.604,327.396,213.856,267.716 nm。结果显示:6种元素的质量浓度分别在1.00 mg·L~(-1)(Pb、As、Cu、Ni)内和2.00 mg·L~(-1)(Cr、Zn)内与其对应的光谱响应值呈线性关系,检出限(3s)为0.29～5.76μg·L~(-1);对标准样品进行6次重复测定,测定值的相对标准偏差为0.60%～2.6%,测定值与认定值基本一致。     

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.     

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%).     

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.     

Synthesis of N-substituted carbazolones from α-iodo enaminones via Pd(0)-catalyzed intramolecular coupling under microwave irradiation

A variety of N-aryl and N-alkyl carbazolones were conveniently achieved in good to high yields via Pd₂(dba)₃-mediated intramolecular coupling of N-substituted α-iodo enaminones under microwave irradiation. The Pd(0)-catalyzed cyclization was found to proceed favorably with the more electron-deficient phenyl ring during the reactions involving unsymmetrical N,N-diaryl α-iodo enaminones. This unique property enables the construction of carbazolone skeleton containing nitro substituted benzenoid ring.     

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.     

Synthesis of substituted 2,4,5,6-tetrahydrocyclopenta[c]pyrazoles and 2,4,5,6-tetrahydropyrrolo[3,4-c]pyrazoles by intramolecular nitrilimine cycloaddition

Both substituted 2,4,5,6-tetrahydrocyclopenta[c]pyrazoles and 2,4,5,6-tetrahydropyrrolo[3,4-c]pyrazoles have been synthesized by the 3+2 intramolecular dipolar cycloaddition of nitrilimines to alkynes. This cyclization has been extended to more versatile 3-bromo derivatives by the use of alkynylbromides as dipolarophiles.     

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.