紫外-可见-短波近红外漫反射光谱技术测定白芷中二氧化硫残留量的研究

建立紫外-可见-短波近红外漫反射光谱结合化学计量学测定白芷中二氧化硫残留量的方法。利用紫外-可见-短波近红外漫反射光谱技术并结合化学计量学建模预测二氧化硫残留量。偏最小二乘回归法(PLSR)建模优于支持向量回归法(SVR); Random Frog波段选择结合Auto-scaling预处理后PLS建模后预测效果最佳,校正集R~2为0. 99,交叉验证集R~2为0. 94,预测集R~2为0. 96。紫外-可见-短波近红外漫反射光谱结合化学计量学可以实现二氧化硫残留量的快速检测,为中药饮片的质量评价及监管提供一种技术手段。     

同步荧光法同时测定溶解态的菲与2-乙基菲

将同步荧光法结合人工神经网络(ANN)和支持向量回归(SVR)用于混合体系中荧光光谱重叠的菲(Phe)和2-乙基菲(2-EP)两组分的同时测定。通过三维同步荧光法结合平行因子(PARAFAC)分析寻得Phe和2-EP的特征波长差Δλ为118 nm。在220~280 nm范围内,以31个波长处荧光强度值作为模型的输入变量用于建立ANN和SVR模型。结果显示,ANN模型分析Phe和2-EP预测样本的回收率分别为92.5%~104.9%和96.1%~104.3%,预测均方根误差(RMSEP)分别为2.08和2.95;SVR模型分析预测样本的回收率分别为98.2%~101.3%和94.9%~104.2%,RMSEP分别为0.74和2.42。实际水样的加标回收实验显示,基体简单的矿泉水中两种模型均取得满意结果;而基体复杂的湖水中样品预测值较实际值低,且SVR模型比ANN的预测性能更加稳健,泛化能力更强。将同步荧光法结合SVR模型应用于Phe和2-EP单独及混合状态下与腐植酸(HA)相互作用的研究,结果显示混合体系中Phe和2-EP与HA的结合系数均小于各自单组分体系,表明Phe和2-EP之间存在竞争吸附。     

白酒基酒中酮类物质的近红外光谱检测方法

应用近红外光谱技术建立了白酒基酒中2,3-丁二酮和3-羟基-2-丁酮的快速检测模型。从洛阳杜康酒厂选取182个白酒基酒样品为材料,运用气相色谱法测得两种物质的化学值,同时采集其在12 000~4 000 cm-1范围内的光谱数据,采用偏最小二乘法(PLS)结合内部交叉验证建立校正模型。通过对比不同光谱预处理下PLS模型效果对其进行优化,确定2,3-丁二酮和3-羟基-2 丁酮的最佳预处理方法分别为一阶导数+多元散射校正和二阶导数,最佳光谱区间分别为9 403.2~7 497.9 cm-1和9 403.2~7 497.9 cm-1+6 101.7~5 449.8 cm-1。优化后2,3-丁二酮和3 羟基-2-丁酮校正集样品的化学值和近红外预测值的决定系数(R2)分别为0.960 2和0.963 2,交叉验证均方根误差(RMSECV)分别为0.39、0.22 mg/100 mL;通过外部检验,验证集样品的R2分别为0.957 6和0.957 8,预测均方根误差(RMSEP)分别为0.40、0.24 mg/100 mL。结果表明,应用近红外光谱技术结合化学计量学方法所建立的模型有较高的准确度,能够满足白酒生产中酮类物质的快速检测需要。     

应用近红外漫反射光谱法的猕猴桃品质无损检测北大核心CSCD

应用近红外漫反射光谱技术和化学计量学,研究成熟期猕猴桃内部品质与其近红外漫反射光谱之间的关系。在室温(24±2)℃下,采集猕猴桃赤道区域不同测试部位在4 000~10 000 cm^(-1)范围内的光谱数据,用基于平滑处理、归一化及基线校正的组合式处理方法对原始光谱进行预处理;另应用偏最小二乘(PLS)法、主成分回归法和多元线性回归法等方法分别建立猕猴桃硬度、可溶性固形物含量(SSC)的校正模型。结果表明:采用组合预处理方法和PLS法建立的校正模型精度最高;硬度校正集相关系数R_c、均方根误差RMSEC和预测集相关系数R_p、均方根误差RMSEP达到了0.976 5,0.548 3,0.943 2,0.612 7;SSC校正集相关系数R_c、均方根误差RMSEC和预测集相关系数R_p、均方根误差RMSEP达到了0.916 6,0.539 6,0.901 2,0.619 0;试验结果验证了本法的可行性。     

应用近红外漫反射光谱法的猕猴桃品质无损检测

应用近红外漫反射光谱技术和化学计量学,研究成熟期猕猴桃内部品质与其近红外漫反射光谱之间的关系。在室温(24±2)℃下,采集猕猴桃赤道区域不同测试部位在4 000~10 000 cm~(-1)范围内的光谱数据,用基于平滑处理、归一化及基线校正的组合式处理方法对原始光谱进行预处理;另应用偏最小二乘(PLS)法、主成分回归法和多元线性回归法等方法分别建立猕猴桃硬度、可溶性固形物含量(SSC)的校正模型。结果表明:采用组合预处理方法和PLS法建立的校正模型精度最高;硬度校正集相关系数R_c、均方根误差RMSEC和预测集相关系数R_p、均方根误差RMSEP达到了0.976 5,0.548 3,0.943 2,0.612 7;SSC校正集相关系数R_c、均方根误差RMSEC和预测集相关系数R_p、均方根误差RMSEP达到了0.916 6,0.539 6,0.901 2,0.619 0;试验结果验证了本法的可行性。     

支持向量回归-同步荧光光谱法预测鸭肉中克百威残留

为了满足鸭肉中克百威残留分析及快速检测的要求,基于克百威水解物在巯基乙醇存在的条件下能与邻苯二甲醛反应产生具有强荧光性衍生物的方法,建立了应用同步荧光光谱法测定鸭肉中克百威残留量的预测模型。对含有克百威鸭肉样品的三维同步荧光光谱进行分析,确定其最佳波长差Δλ为120 nm;利用遗传算法(GA)结合交互验证均方根误差(RMSECV)从240～450 nm光谱中筛选出19个波长作为定量分析模型的输入特征变量;对SVR、PCR、PLS 3种回归模型的性能进行比较,实验发现SVR模型的预测结果最好,其预测集的决定系数(r2)和预测均方根误差(RMSEP)分别为0.999 4和0.878 7。研究结果表明,采用同步荧光光谱法结合支持向量回归算法测定鸭肉中克百威的残留量,具有快速、预测精度高等特点,可为检测鸭肉中的克百威残留量提供一种可行的方法。     

紫外光谱法结合化学计量学用于环境水样中2,4,6-三硝基甲苯及其分解物的同时测定

结合紫外吸收和偏最小二乘法建立了环境水样中2,4,6-三硝基甲苯及其分解物的分析方法,在不经过任何预先分离的情况下,实现了环境水样中2,4,6-三硝基甲苯(TNT)及其分解物2,4-二硝基甲苯(2,4-DNT)和2,6-二硝基甲苯(2,6-DNT)的快速准确测定.采用正交试验设计(OAD)配制了25个训练集样本和15个独立预测集样本,采用变量种群分析(VCPA)方法挑选特征变量以提高偏最小二乘法(PLS)模型的预测效果,预测集中每个物质的相关系数R2均达到0.99.将最优的VCPA模型用于真实水样中TNT以及DNT的检测,并采用HPLC方法进行了验证.实验结果显示,VCPA模型的回收率与HPLC法相近.紫外光谱法结合化学计量学方法可作为环境体系中多成分同时测定的一种简便、快速、有效的方法.     

基于近红外光谱技术的日照绿茶茶鲜叶模型的优化

建立一种茶鲜叶中茶多酚含量的快速测定方法。采取日照市2个主要茶叶产区60个茶园的茶鲜叶,利用近红外光谱技术结合化学计量学方法建立优化模型进行预测。茶多酚的参考值采用国家标准方法进行测定。结果表明,采用Savitzky-Golay平滑和一阶导数处理光谱,能够有效消除光谱中的噪音及非目标因素的影响。遗传算法(Genetic Algorithm,GA)选择了针对目标组分茶多酚的200个信息变量,简化了模型。同时,采用主成分回归(PCR)和偏最小二乘(PLS)两种建模方法进行预测,其预测均方根误差(RMSEP)及剩余预测偏差(RPD)分别为0.6158、0.6743和4.7238、4.3141;决定系数(R2)分别为0.9514和0.9451。     

葡萄籽多酚大孔树脂纯化过程的近红外光谱快速检测

采用近红外光谱透射法,对葡萄籽提取液大孔树脂层析过程多酚含量进行快速无损测定.以FolinCiocalteus比色法为对照方法,运用偏最小二乘法(PLS)建立定量校正模型,测定大孔树脂洗脱过程葡萄籽多酚浓度变化.该模型相关系数R2达到0.9995,校正集误差均方根(RMSEC)和预测集误差均方根(RMSEP)分别为0.713和2.67,校正集相对偏差(RSEC)和预测集相对偏差(RSEP)分别为2.39％和8.48％.本方法快速、有效、无损,可用于葡萄籽多酚柱层析纯化过程检测和质量控制.     

主成分-偏最小二乘分光光度法同时测定饲料中的痕量铁、锰、铜、锌

痕量Fe^3＋、Mn^2＋、Cu^2＋、Zn^2＋与2-（5-溴-2-吡啶偶氮）．5-二乙氨基苯酚（5-Br-PADAP）和对．（1，1，3，3．四甲基丁基）苯基醚（Triton X-100）在pH8．3发生高灵敏显色反应，所形成的三元胶束络合物的吸收光谱严重重叠。本文采用主成分-偏最小二乘法（PC—PLS）辅助分光光度法成功地测定了合成试样及饲料中上述4种痕量组分。结果表明，PC—PLS法是化学计量学法中一种可适用于基体较复杂的实际试样中痕量组分同时分光光度测定的优良的多元计算方法。     

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%.     

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.     

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.     

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.     

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.