多元校正-光度法同时测定食品中的香兰素和乙基麦芽酚

香兰素、乙基麦芽酚在紫外区均有吸收,其吸收光谱严重重叠。在pH=2．87的B-R缓冲溶液中对香兰素和乙基麦芽酚两组分混合溶液进行光度测定,所得重叠光谱数据分别用经典最小二乘法(CLS)、偏最小二乘法(PLS)、主成分回归法(PCR)处理,并用于食品样品的测定,获得了较好的定量分析结果。香兰素和乙基麦芽酚的线性范围均为1．0～20．0mg／L;检出限分别为0．478mg／L和0．559mg／L。     

主成分回归一紫外光度法同时测定盐酸西替利嗪和苯甲酸钠

提出了一种用紫外光度法同时测定盐酸西替利嗪和苯甲酸钠的方法.在pH 4.56的B-R缓冲溶液中对盐酸西替利嗪和苯甲酸钠两组分混合溶液进行吸光度测定,所得的重叠光谱数据用主成分回归法(PCR)和偏最小二乘法(PLS)等化学计量学方法进行处理,结果表明主成分回归(PCR)的预报误差最小.对实际样品进行测定,回收率为88.8...     

主成分回归校正法-紫外分光光度法同时测定鲜味剂中5′-肌苷酸二钠和5′-鸟苷酸二钠

提出了一种用紫外分光光度法同时测定5′-肌苷酸二钠(IMP)和5′-鸟苷酸二钠(GMP)的方法,在pH 6.80的B-R缓冲溶液中对尼泊金乙、丙酯钠两组分混合溶液进行光度测定,所得的重叠波谱数据用经典最小二乘法(CLS)、主成分回归法(PCR)和偏最小二乘法(PLS)等化学计量学方法进行处理,结果表明:PCR的预报误差最低。用标准加入方法作回收试验,测得IMP的回收率在97.1%~114.9%之间,GMP的回收率在98.3%~103.6%之间。     

多元校正-速差动力学分光光度法同时测定三组分有机磷农药

速差动力学分析结合化学计量学对动力学数据进行解析计算, 可扩大动力学分析的范围, 提高分析的准确度. 本文利用对硫磷、甲基对硫磷和杀螟硫磷在碱性介质中能与氧化剂过氧化氢发生氧化反应生成对硝基苯酚的性质, 引入多元校正方法中的经典最小二乘法(CLS)、偏最小二乘法(PLS)和主成分回归法(PCR)对动力学数据进行解析, 实现了三组分人工合成样品的同时测定.     

偏最小二乘-同步荧光法测定人尿中黄蝶呤

建立了人尿中黄蝶呤含量测定的同步荧光分析方法。在pH 7.8 KH2PO4-NaOH缓冲溶液中,于Δλ为70 nm的条件下对黄蝶呤及其它蝶呤类化合物进行同步荧光扫描,所得的重叠波谱数据用主成分回归法(PCR)、偏最小二乘法(PLS)、经典最小二乘法(CLS)和径向基人工神经网络(RBF-ANN)等多元校正法进行处理,结果表明偏最小二乘法(PLS)的分析结果最好,其标准偏差为4.29%。该方法简便、快速、准确,避免了较繁琐的样品前处理过程,应用于人尿中黄蝶呤分析,结果令人满意。     

人工神经网络-微分脉冲伏安法同时测定尿液中的多巴胺、尿酸及抗坏血酸

研究了多巴胺、尿酸和抗坏血酸在玻碳电极上的伏安行为.在pH 5.7的Britton - Robinson缓冲溶液中,采用微分脉冲伏安法进行电化学扫描,3种化合物均有良好的氧化峰,但其波谱重叠严重,常规伏安法难以同时测定.采用化学计量学方法中的偏最小二乘法(PLS)、主成分回归法(PCR)、径向基人工神经网络法(RBF-...     

化学计量学分光光度法同时测定钢铁中镧和铈

在pH 3．0的缓冲溶液中,镧(Ⅲ)、铈(Ⅲ)与偶氮胂-Ⅲ均发生高灵敏度的显色反应,生成稳定的配合物。其λmax均为657 nm,镧(Ⅲ)、铈(Ⅲ)含量在0～1．0 mg·L-1范围内符合比耳定律,两者吸收光谱严重重叠。采用偏最小二乘法和主成分分析法用于普碳钢、铸铁等试样中镧和铈的测定,合成试样分析结果的相对误差小于10％。     

用近红外透射光谱技术测定精米蛋白质含量研究

应用近红外透射光谱技术．采用3种不同回归统计分析方法建立业米蛋白质含量(PC)定量回归方程。结果表明,用改进的最小二乘法(MPLS)、偏最小二乘法(PLS)和主成分回归法(PCR)进行饺正时．校正标准误差(SEC)、交叉检验标准误差(SECV)分别为0．1258、0．134O(MPLS)．0．1177、0．1175(PLS)．0．1207、0．1275(PCR)校正相关系数(RSQ)和交叉验证相关系数(1-VR)分别为0．9941、0．9931(MPLS)．0．9950、0．9942(PLS)．0．9947、0．9942(PCR)。由此可见,3种回归统计方法在建立业米蛋白质含量回归方程时差异不明显．都具有较好的预测效果。近红外透射光谱法作为一种快速而准确的定量分析手段,在稻米加工企业品质管理、大米品质分析和大米贸易检测上有广阔的应用前景。     

流动注射在线稀释测高浓度的铁

用自行组装的流动注射 智能测铁仪对高浓度铁(Ⅱ)和铁(Ⅲ)进行在线稀释测定,该仪器的分析结果与FIA 721B型分光光度计法分析结果进行比较,结果表明,该方法有快速、准确等优点。其测量的线性范围是:铁(Ⅱ)和铁(Ⅲ)分别为0.10～5.00mg·L-1和0.10～4.50mg·L-1,采用在线稀释后为0.50～30.00mg·L-1铁(Ⅱ)和0.50～20.00mg·L-1铁(Ⅲ)。测定频率为40个样品·h-1;RSD<5%,能满足工业企业分析监测的需要。     

偏最小二乘法及主组分回归法用于药物组分的测定

本文研究了多元校准方法——偏最小二乘法(PLS)和主组份回归法(PCR)在药物多组份光度分析中的应用,获得了较满意的结果。而且在系列校准样品的实验设计、交叉证实法确定最佳因子数以及空缺组份体系的分析等方面进行了探讨。     

TIN AND GERMANIUM COMPLEXES WITH MALTOL

Abstract

The reaction of tin and germanium tetrachlorides with 3-hydroxy-2-methyl-4H-pyran-4-one (HMa) in benzene yielded M(HMa)₄Cl₄·C₆H₆ (M = Sn or Ge) adducts, whereas in methanol the MMa₂Cl₂ complexes have been isolated. Moreover, tin complexes with the neutral donors 2,6-dimethyl-4H-pyran-4-one (DMP) and 2,6-dimethyl-4H-pyran-4-thione (DMTP), having formulae Sn(L)₂Cl₂ and Sn(L)₂Cl₄(L = DMP or DMTP) have been prepared. The compounds have been characterized by ir and proton nmr spectroscopy and by thermogravimetric (TG and DTA) analysis. The thermal behaviour of all complexes has been followed to 1200°C. The stability of the M(HMa)₄Cl₄ adducts in various solvents is discussed on the basis of proton nmr spectra.     

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%.     

CoFe2O4自形成磁性液体场致结构化对磁化的影响

The Langevin paramagnetic theory can’t describe the relation between magnetization of ferrofluids and applied magnetic field. The structuralization of ferrofluids, which is considered the main influence factor of the magnetization, is regarded. The part of magnetization works is deposited when the structure is forming. This action influences the magnetization of ferrofluids directly or indirectly. On the base of the “compressing” model, the Langevin function that usually describes the magnetization of ferrofluid is modified, and a well-fitted curve is obtained. An equation of the relation between the equivalent volume fraction after being “compressed” and the intensity of magnetic field is discovered, which approximately describes the process of magnetization. The relation between the approximate initial susceptibility and the volume fraction can be obtained from modified formula.     

Highly regioselective Buchwald–Hartwig amination at C-2 of 2,4-dichloropyridine enabling a novel approach to 2,4-bisanilinopyridine (BAPyd) libraries

The highly regioselective Buchwald–Hartwig amination at C-2 of the cheap and readily accessible reagent, 2,4-dichloropyridine with a range of anilines and heterocyclic amines is described. This new methodology is robust and provides a facile access to 4-chloro-N-phenylpyridin-2-amines on 0.25 mol scale. These intermediates undergo a further Buchwald–Hartwig amination at higher temperature to enable rapid exploration of the chemical space at C-4 and to provide a library of 2,4-bisaminopyridines.     

Sulfur-directed metal-free and regiospecific methyl C(sp3)–H imidation of thioanisoles

Regiospecific and direct imidation of the methyl C(sp³)–H bond of thioanisoles is realized under mild and metal-free conditions with N-fluorobis(benzenesulfonyl)imide as an oxidant and nitrogen source. Proposed mechanism suggests that thionium ion intermediates and a Pummerer-type reaction are involved. The imidation has advantages such as high step-economy, excellent functionality tolerance, and regiospecificity, giving structurally diverse imidation products.     

Selective syntheses of 2H-1,3-oxazines and 1H-pyrrol-3(2H)-ones via temperature-dependent Rh(II)-carbenoid-mediated 2H-azirine-ring expansion

The Rh(II)-catalyzed reaction of 2-carbonyl-substituted 2H-azirines with ethyl 2-cyano-2-diazoacetate or 2-diazo-3,3,3-trifluoropropionate provides an easy access to 2H-1,3-oxazines and 1H-pyrrol-3(2H)-ones. These compounds can be selectively prepared from the same starting material using temperature as the only varied parameter. The 2-azabuta-1,3-diene intermediate, a common precursor for both heterocyclic products, isomerizes into 2H-1,3-oxazine under kinetic control, while 1H-pyrrol-3(2H)-one is the sole product of the reaction at elevated temperatures. According to DFT-calculations a one-atom oxazine ring contraction involving ring-opening to a 2-azabuta-1,3-diene intermediate, followed by a 1,5- and 1,2-prototropic shift leads to the consecutive formation of imidoylketene and azomethine ylide, which then further undergo cyclization to the pyrrole derivative.     

Copper catalyzed/mediated synthetic methodology for ebselen and related isoselenazolones

Scope of the copper catalyzed/mediated selenium-nitrogen coupling reaction has been studied for the synthesis of isoselenazolones. It is noticed that the 2-chloro, 2-bromo-, and 2-iodo-aryl amides substrates can be exploited in the selenium-nitrogen coupling reaction by employing 25-100 mol % of CuI/1,10-phenanthroline (L) and potassium carbonate as a base in DMF. Furthermore, electron rich 2-chloro-arylamides also underwent selenium-nitrogen coupling reaction to give biologically important selenium-nitrogen heterocycles. Also, copper-catalyzed selenium-nitrogen coupling reaction has been meticulously applied for the synthesis of diaryl diselenides having methoxy, amine, and amide functionality from respective aryl iodides in the presence of stoichiometric amount of succinimide as an external Se-N coupling partner.     

Knoevenagel condensation catalyzed by novel Nmm-based ionic liquids in water

A series of novel N-methyl morpholine (Nmm) based ionic liquids with 1,2-propanediol group were synthesized and used as catalysts for Knoevenagel condensation at room temperature in water. Under the effect of the catalyst, various aldehydes or aliphatic ketones could react with a wide range of activated methylene compounds well, including malononitrile, alkyl cyanoacetate, cyanoacetamide, β-diketone, barbituric acid, 2-arylacetonitrile and thiazolidinedione. Furthermore, most of the products could be separated just by filtrating and washing with water. Additionally, the catalyst is recyclable and applicable for the large-scale synthesis.     

Construction of polyheterocyclic spirotetrahydrothiophene derivatives via sulfa-Michael/aldol cascade reaction

A series of polyheterocyclic spirotetrahydrothiophene derivatives were obtained in moderate to excellent yields via a catalyst-free sulfa-Michael/aldol cascade reaction of chalcones 1 and commercially available 1,4-dithiane-2,5-diol 2 under mild conditions. We also present the first asymmetric sulfa-Michael/aldol cascade reaction of chalcones 1 and commercially available 1,4-dithiane-2,5-diol 2 with moderate to good enantioselectivities catalyzed by readily available chiral phase-transfer catalysts (PTCs).