Determination of trace levels of pyrethroid metabolites in human urine by capillary gas chromatography-high resolution mass spectrometry with negative chemical ionization

Summary Applications of high-resolution gas chromatography and high-resolution mass spectrometry (GC-MS) for identification and quantitation of trace amounts of pyrethroid metabolites in human urine samples are demonstrated. The method covers the pyrethroid metabolitescis- andtrans-3-(2,2-dichlorovinyl)-2,2-dimethyl-cyclopropane carboxylic acid (cis- andtrans-DCCA),cis-3-(2,2-dibromovinyl)-2,2-dimethylcyclopropane carboxylic acid (cis-DBCA), 4-fluoro-3-phenoxybenzoic acid (FPBA), and 3-phenoxybenzoic acid (3-PBA). After acid-induced hydrolysis of urine samples and exhaustive solvent extraction, a carbodiimide-coupled esterification of the free carboxylic acids with hexafluoroisopropanol (HFIP) is applied. Identification of the derivatives formed is achieved by low-resolution electron-impact mass spectrometry (EIMS) using an ion-trap detector. Quantitation was by capillary gas chromatography—high-resolution mass spectrometry using negative chemical ionization (GC-NCIMS). 2-Phenoxybenzoic acid (2-PBA) served as internal standard. The limits of detection forcis- andtrans-DCCA,cis-DBCA, FPBA and 3-PBA were 0.03 μg L⁻¹ or below. The applicability of the presented method was tested on urine samples of persons exposed to low levels of pyrethroids.     

含磷杂环化合物的重排反应、互补离子及取代基效应

本文应用电子轰击质谱(EIMS)及亚稳离子的测定技术,研究了十四种新合成的含磷杂环化合物的碎裂机理,着重探讨了此系列化合物的重排反应、互补离子及取代基效应对离子丰度的影响。     

Nano-liquid chromatography-direct electron ionization mass spectrometry: improving performance by a new ion source adapter

A novel interface adapter has been designed to provide a new way of directly coupling a nano-liquid chromatograph to an electron ionization mass spectrometer. It connects the transfer capillary coming from the liquid chromatograph to the ionization chamber and can be easily screwed into the ion source. Liquid coming from the column passes through the heated adapter flow path and is vaporized. A continuous flow of new liquid pushes the vapor into the ionization chamber where it is ionized and continues on to the mass analyzer. The advantages of the new adapter are reduced ice formation inside the ion source and less clogging of the transfer capillary. Improvements achieved are demonstrated on the basis of caffeine and steroid analysis. The limits of detection of selected steroids are compared with and without the adapter. The adapter improves the detection limit of the system by a factor of 2 and precision from ≤15% to ≤9% relative standard deviation. No derivatization procedure is necessary before the analysis of small polar compounds. The resulting spectra are reproducible, easily interpretable, and database searchable. The new method is robust, delivers reproducible results, and provides a highly efficient alternative to existing methods in the field of pharmaceutical analysis.     

Numerical Analysis of the Mixed 4th-Order Runge-Kutta Scheme of Conditional Nonlinear Optimal Perturbation Approach for the EI Niño-Southern Oscillation Model

In this paper, we propose and analyze the mixed 4th-order Runge-Kutta scheme of conditional nonlinear perturbation (CNOP) approach for the EI Niño-Southern Oscillation (ENSO) model. This method consists of solving the ENSO model by using the mixed 4th-order Runge-Kutta method. Convergence, the local and global truncation error of this mixed 4th-order Runge-Kutta method are proved. Furthermore, optimal control problem is developed and the gradient of the cost function is determined.     

EI~n代数与*EI~n代数

为了更好地解决模糊概念的表示问题 ,文 [1]、 [2 ]引入了 AFS.代数和 AFS.结构。为了讨论AFS.结构的拓扑性质 ,本文在 [1]、 [2 ]的基础上 ,进一步讨论了 EIn 代数和 * EIn 代数的性质与结构。     

Asymptotic solution for EI Ni$$ \overset{\lower0.5em\hbox{$\smash{\scriptscriptstyle\smile}$}}{n} $$o-southern oscillation of nonlinear model

A class of nonlinear coupled system for EI Nino-Southern Oscillation （ENSO） model is considered. Using the asymptotic theory and method of variational iteration, the asymptotic expansion of the solution for ENSO models is obtained.     

质谱法分析季铵盐型阳离子表面活性剂

以电子轰击质谱法(EI/MS)与电喷雾质谱法(ESI/MS)相结合,分析季铵盐型表面活性剂。由于阳离子表面活性剂在水溶液中离解成正离子,可用电喷雾质谱的正离子模式(ESI /MS)对其结构及组成进行鉴定,同时可判别季铵盐所含的Cl-、Br-、NO3-等阴离子。     

一系列色烯类化合物的EI质谱分析

色烯类化合物是一类具有生物活性的杂环化合物,为了研究色烯类衍生物的抗癌活性,设计合成了一系列该类化合物。该类化合物E I质谱数据表现出了很好的规律性,都给出了m/z186碎片离子峰,推测该碎片离子以3个共振结构式互变的形式稳定存在。本文报道了这类化合物的E IMS以及主要碎裂途径。     

EI代数

为了更好地解决模糊概念的表示问题,文[1]引入了AFS代数和AFS结构,为了讨论AFS代的拓扑性质,本文在[1]的基础上,进一步了讨论了EI代数的性质与结构,并对其子代数EM－{φ}的性质和结构进行了讨论。     

*EI代数上的拓扑分子格及其在聚类分析中的应用

在AFS代数和AFS结构的基础上,通过对AFS代数上的拓扑分子格结构的讨论,给出了EM中,由一些模糊概念生成的拓扑分子格所诱导出的X上拓扑的几点性质,并利用这些性质,对一个实际例子构造了隶属函数进行聚类分析,说明了这些性质在聚类分析中的应用。