Rapid analysis of multicomponent pesticide mixture by GC-MS with the aid of chemometric resolution

Applications of hyphenated chromatographic techniques, especially GC-MS technique, have been reported in chemical, biological, environmental, agricultural and medical analysis. The complexity of the samples in these fields is still an obstacle for the technique to be practical and the overlapping of the multicomponent signals induces chemometric methods widely employed. In this work, taking the rapid analysis of pesticide mixture as an example, a chemometric approach was proposed for resolution of multicomponent overlapping GC-MS signal. In the method, a mass spectral library of pesticides was organized at first, then target factor analysis (TFA) was employed for testing the existence of a specific pesticide in the multicomponent overlapping GC-MS signal, and finally the chromatographic information of the pesticide was extracted by a non-negative immune algorithm (IA). A GC-MS signal of a 40-component pesticide mixture eluted within 9 min was analyzed by the method. It was found that the mass spectra and chromatographic profiles of almost all the pesticides can be obtained.     

Simultaneous determination of mercury, lead and cadmium ions in water using near-infrared spectroscopy with preconcentration by thiol-functionalized magnesium phyllosilicate clay

Analysis of metal ions in environment is of great importance for evaluating the risk of heavy metal to public health and ecological safety. A method for simultaneous determination of metal ions in water samples was developed by using adsorption preconcentration and near-infrared diffuse reflectance spectroscopy (NIRDRS). A high capacity adsorbent of thiol-functionalized magnesium phyllosilicate, named Mg-MTMS, was prepared by co-condensation for preconcentration of Hg²⁺, Pb²⁺ and Cd²⁺ in aqueous solutions. After adsorbing the analytes onto the adsorbent, NIRDRS was measured and PLS models were established for fast and simultaneous quantitative prediction. Because the interaction of the ions with the functional group of the adsorbent can be reflected in the spectra, the models built with the samples prepared by river water were proven to be efficient enough for precise prediction. The determination coefficients (R²) of the validation samples for the three ions were found as high as 0.9197, 0.9599 and 0.9861, respectively. Furthermore, because the high adsorption efficiency of Mg-MTMS, the detected concentrations are as low as milligrams per liter for the three ions, and the concentration can be further reduced. Therefore, the feasibility of quantitative analysis metal ions in river water by NIRDRS is proven and this may provide a new way for fast simultaneous determination of trace metals in environmental waters.     

Predicting the coordination geometry for Mg2+ in the p53 DNA-binding domain: insights from computational studies

Zn(2+) in the tumor-suppressor protein p53 DNA-binding domain (DBD) is essential for its structural stability and DNA-binding specificity. Mg(2+) has also been recently reported to bind to the p53DBD and influence its DNA-binding activity. In this contribution, the binding geometry of Mg(2+) in the p53DBD and the mechanism of how Mg(2+) affects its DNA-binding activity were investigated using density functional theory (DFT) calculations and molecular dynamics (MD) simulations. Various possible coordination geometries of Mg(2+) binding to histidines (His), cysteines (Cys), and water molecules were studied at the B3LYP/6-311+g** level of theory. The protonation state of Cys and the environment were taken into account to explore the factors governing the coordination geometry. The free energy of the reaction to form the Mg(2+) complexes was estimated, suggesting that the favorable binding mode changes from a four- to six-coordinated geometry as the number of the protonated Cys increases. Furthermore, MD simulations were employed to explore the binding modes of Mg(2+) in the active site of the p53DBD. The simulation results of the Mg(2+) system and the native Zn(2+) system show that the binding affinity of Mg(2+)to the p53DBD is weaker than that of Zn(2+), in agreement with the DFT calculation results and experiments. In addition, the two metal ions are found to make a significant contribution to maintain a favorable orientation for Arg248 to interact with putative DNA, which is critically important to the sequence-specific DNA-binding activity of the p53DBD. However, the effect of Mg(2+) is less marked. Additionally, analysis of the natural bond orbital (NBO) charge transfer reveals that Mg(2+) has a higher net positive charge than Zn(2+), leading to a stronger electrostatic attractive interaction between Mg(2+) and putative DNA. This may partly explain the higher sequence-independent DNA-binding affinity of p53DBD-Mg(2+) compared to p53DBD-Zn(2+) observed in experiment.     

Resolution of multicomponent NMR signals using wavelet compression and immune algorithm

A novel algorithm for fast resolution of multicomponent overlapping nuclear magnetic resonance (NMR) spectrum using the wavelet compression and the immune algorithm (IA) is proposed. Taking advantage of the linear property of the wavelet transform (WT), the overlapping NMR spectrum (antigen) can be compressed by WT before it is input into the immune network, the antibodies are also compressed to the same scheme. After extraction of the compressed information of each component, the resolved NMR spectra can be restored by the WT reconstruction. It was proven that the result is almost the same with the result from an IA, but the calculation speed is much faster.     

Simultaneous Identification and Quantitative Determination of Amino Acids in Mixture by NMR Spectroscopy Using Chemometric Resolution

Nuclear magnetic resonance (NMR) spectroscopy receives increasing interest in biological and metabolomic studies. It is still, however, a great challenge to analyze the NMR spectra of multicomponent samples, containing overlapping responses of the compositions. In this work, nonnegative independent component analysis (nonnegative ICA) and immune algorithm (IA) were employed for simultaneous identification and quantitative determination of three amino acids in mixture samples from measured multicomponent NMR signals. Results show that the correlation coefficients (R) between the extracted and measured spectra are higher than 0.97 and that those between the calculated relative contents and experimental ones are higher than 0.99. The method may provide an alternative technique for analyzing multicomponent samples like biofluids by using NMR spectroscopy.     

材料封装型光纤布拉格光栅宽温域应变传感性能研究

针对用于高温油气井下的光纤布拉格光栅(FBG)传感器弹性封装材料宽温域应变问题,将奥氏体不锈钢材料和试制的铌基恒弹合金材料设计加工成弹性应变元件,并将FBG粘贴于其上封装成传感器.在30～250℃宽温域范围内对两个传感器施加拉力进行应变传感实验,对比研究了两种材料的应变传感性能.结果 表明:两种合金材料在不同温度下的应变响应线性度均超过0.999;但随着温度的升高,两种合金材料的应变响应灵敏度有下降趋势,重复性降低,迟滞增大,温度影响弹性材料的应变传感性能;在30～250℃温度范围内,用试制的铌基恒弹合金材料封装的传感器在重复性、迟滞、线性拟合度和灵敏度稳定性方面均优于奥氏体不锈钢材料封装的传感器.因此试制的铌基恒弹合金可用于宽温域FBG传感器的弹性封装材料.     

大范围光纤布拉格光栅温度传感器增敏实验研究

简要分析了光纤布拉格光栅的温度响应及增敏原理,采用特殊耐高温有机聚合物对光纤光栅进行温度增敏封装,并通过改进光纤光栅的聚合物封装固化工艺,使用某种有机硅导热胶减小有机聚合物与套管材料的粘合度,消除了封装过程中由于聚合物材料不均匀收缩引起的光纤光栅反射谱啁啾化,实现20～180℃范围内光纤光栅传感器对温度高灵敏度测量。实验结果表明．聚合物封装光纤光栅传感器温度响应灵敏度在20～130℃为0．05nm／℃,在130～180℃达到了0．22nm／℃,并在两个区域保持较好的线性与重复性。此结构传感器封装工艺简单,易于实现,可用于高温恶劣环境下的温度单参量测量。     

Hydrocracking of Tar Components from Hot Coke Oven Gas over a Ni/Ce-ZrO2/γ-Al2O3 Catalyst at Atmospheric Pressure

Ni/Ce-ZrO₂/γ-Al₂O₃ catalysts with different Ce-ZrO₂ contents and Ni loadings were prepared by a two step impregnation method and characterized by X-ray diffraction, transmission electron microscopy, N₂ adsorption, and temperature-programmed reduction. The catalysts were used for the hydrocracking of toluene and naphthalene, which were model tar compounds in hot coke oven gas, under atmospheric pressure at 800 °C. They showed excellent catalytic activity, stability, and some sulfur tolerance. Both toluene and naphthalene was converted into light fuel gases even at a low mole ratio of steam to carbon (S/C = 0.44). During the testing period of 7 h, no coke deposition was observed on the surface of the catalysts. The results indicated that the addition of Ce-ZrO₂ limited the sintering of Ni particles and enhanced the catalytic activity. The Ni/Ce-ZrO₂/γ-Al₂O₃ catalyst is promising for the direct removal of tar compounds in hot coke oven gas with low S/C ratios.     

直链烷烃近红外光谱的温度效应与应用研究

近红外光谱的温度效应已得到关注,在结构分析和定量分析方面得到了尝试.以直链烷烃为例,对烷烃有机体系近红外光谱的温度效应进行了研究.采集了20~60℃范围内五种直链烷烃(正己烷到正癸烷)及其混合物的近红外光谱并进行了对比分析,仅发现某些谱峰的强度随温度发生微小变化.采用交替三线性分解算法对光谱数据进行了解析,考察了光谱的特征以及随温度和结构的变化.结果表明,链端C₂H₅和链中CH₂基团的光谱受温度的影响不同,但其光谱信号的强度与温度之间都具有良好的线性关系,可根据光谱预测体系的温度;两种基团的光谱信号强度与烷烃分子的碳数或两种基团在分子中相对含量都具有良好的线性关系,可用于直链烷烃混合物组成的估算.