离子色谱法同时测定叶菜中的硝酸盐和亚硝酸盐

采用抑制型离子色谱法同时测定叶菜中的硝酸盐和亚硝酸盐的含量。色谱柱为Ionpac AS11柱，流动相为21mmol/L NaOH溶液，检测器为电导检测器（CD），流动相流速为1.0mL/min。该方法简便、快捷，准确度和灵敏度高，NO2^-和NO3^-的回收率分别为97％－105％和95％－104％，相对标准偏差RSD＜5．0％。同时考察了样品浸提时间对结果的影响。     

气相分子吸收光谱法测定地下水中亚硝酸盐氮、氨氮、硝酸盐氮

采用气相分子吸收光谱法测定地下水中的亚硝酸盐氮(NO2^-)、氨氮(NH4^+)、硝酸盐氮(NO3^-)。考察NO2^-,NH4^+和NO3^-测定时的相互干扰,并给出了相应的消除方法。研究结果表明,测定NO2^-时,NH4^+和NO3^-无干扰;NO2^-对测定NH4^+和NO3^-产生干扰,可分别采用分段法和加入2滴10%氨基磺酸溶液的方法消除干扰;对于不含NO2^-或NO2-含量不高的地下水样品,可简化操作步骤直接测定NO3^-。该方法测定结果的相对标准偏差为0.73%~2.74%(n=12),样品加标回收率为97.67%~100.28%。所用检测仪器具有流动注射、自动进样及在线绘制标准曲线的功能,简化了标准方法中的样品前处理过程,减少了样品的损失,实现了自动化分析,大幅提高了检测结果的准确度和工作效率。     

离子色谱法检测烟叶中的NO3-、NO2-、Cl-

研究了离子色谱法检测烟叶中阴离子的方法。采用美国Dionex公司DX－500型离子色谱仪，以3.5mmol/L Na2CO3-1.0mmol/L NaHCO3作为淋洗液，流速为1.2mL/min，测定烟叶中的NO3^-、NO2^-、Cl^-等阴离子含量。各种离子在检测条件下有很好的线性，相关系数r=0.9986-0.9997,NO3^-、NO2^-和Cl^-的检出限分别为0.200、0.125和0.064μg/mL。     

离子色谱法测定粮食鲜样中的硝酸盐含量

粮食鲜样经超声提取后，用离子色谱法测定浸提液中的硝酸盐。采用DX-100型离子色谱仪．以2．7mmol／L Na2CO3—0．3mmol／LNaHCO3的混合溶液作为淋洗液，流速为1．2mL／min，测定玉米、大豆、小麦中的NO3^-含量。NO3^-浓度在0．5—40．0mg／L范围内与色谱峰高呈良好的线性关系，相关系数r=0．9995，检出限为0．05mg／L，测定结果的相对标准偏差小于5％．加标回收率为96．0％-100．7％。     

离子色谱法测定米酒中NO-3和NO-2

研究了用带电导检测器的离子色谱对米酒中阴离子NO3^-、NO2^－进行分离测定的方法。NO3^-、NO2^－的线性范围分别为0．5－80mg/L和0.1-20mg/L，检出限分别为0.5mg/L和0.1mg/L。该法适用于SO4^2-、CI^-的测定。     

固相萃取-离子色谱法测定土壤中亚硝酸盐和硝酸盐

提出了离子色谱法测定土壤中亚硝酸盐和硝酸盐的方法。土壤试样经水超声浸取,采用OnGuardⅡP和OnGuardⅡRP固相萃取柱净化,以AS11-HC为分析柱、AG11-HC为保护柱,萃取液中的NO2-和NO3-用15mmol·L-1氢氧化钾溶液洗脱分离,并用抑制电导检测器同时测定其含量。亚硝酸盐和硝酸盐质量浓度分别在0.01～1.00mg·L-1和0.10～10.0mg·L-1范围内与对应的峰面积呈线性关系,方法的检出限(3s/k)分别为0.16,0.24μg·g-1。方法的加标回收率分别在85.0%～100%和93.5%～106%之间,相对标准偏差(n=7)分别在2.9%～4.1%和2.2%～3.4%之间。     

抑制型离子色谱法测定白酒中的F-、Cl-、NO2-、H2 PO4-、NO3-

用抑制型离子色谱法测定白酒中的F^-、Cl^-、NO2^-、H2PO4^-、NO3^-。流动相为4mmol／LNa2CO3—3 mmol／LNaHCO3混合溶液，流速为1．5mL／min，进样量为0、5mL，在最佳色谱条件下，5种无机阴离子10min内实现基线分离。F^-、Cl^-、NO2^-、H2PO4^_、NO3^-的检出限分别为0、008、0．012、0、030、0．068、0．077mg／L。测定结果的相对标准偏差分别为1．86％、1．30％、2．06％、1．82％、1．50％，回收率分别为108．0％、94．0％、101．0％、98．7％、94．4％。     

离子色谱法测定马龙茶叶中的F^—、NO2^—、NO3^—

应用离子色谱法测定乌龙茶叶中的F^-、NO2^-和NO3^-。测得3种样品中F^-、NO2^-和NO3^-的含量分别为1.19-1.75、0.000-0.020和0.024-0.058mg/g，回标回收率分别为94.9%、96.7%和93.4%。     

高效液相色谱法测定大鼠神经组织中的硝酸盐和亚硝酸盐

 建立了大鼠神经组织中亚硝酸盐和硝酸盐的高效液相色谱测定方法,以用于研究一氧化氮在糖尿病慢性神经病变中的作用。在1 μmol/L～25 μmol/L的浓度范围内,NO2-和NO3-的峰面积与浓度的线性相关系数>0.991;最低检测浓度分别为0.2 μmol/L和0.5 μmol/L;日内、日间相对标准偏差<14%。对各实验组大鼠的初步测定结果表明,糖尿病组及糖尿病胰岛素(IGF)治疗组的NO2-和NO3-水平均低于对照组。 关键词：高效液相色谱法;一氧化氮;硝酸盐;亚硝酸盐;糖尿病神经病变     

流动注射荧光猝灭法测定磷酸二氢盐

在pH=5.4的（CH2）6N4－HCl缓冲溶液中,建立Ce(Ⅲ）-NaCl-H2PO4-三元荧光熄灭体系,结合流动注射技术和荧光猝死定量数学模型Ln(F0/F)=LnKMF LnK3-LnKF Ln[M],考察Ce(Ⅲ）的阳离子型体测定H2PO4^-的可行性和适用性。实验表明：在20℃,pH=4.0-6.0时,Ce(Ⅲ)的阳离子型体与磷酸根反应,荧光猝灭程度显著;当注射泵转速为70r/min,样品测定速度为50h^-1,NaCl浓度为0．20－0．30mol/L时,H2PO4^-的测定线性浓度区间为0．20－1．80μg/mL,检测限LOD（3δ）=0．003μg/mL,样品回收率为97．3％－99．0％。     

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.     

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.     

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%).     

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.