环境空气与废气中丙烯酸酯类化合物的控制要求及分析方法

综述环境空气与废气中丙烯酸酯类化合物的控制要求及分析方法。对比了国内外生态环境领域环境空气和废气中丙烯酸酯类化合物的分析方法和管理要求。环境空气和废气中丙烯酸酯类化合物主要采用采样罐/固体吸附剂/气袋采样,低温浓缩/溶剂解吸/热脱附进样/直接进样,可采用非极性/中等极性/强极性色谱柱分离,气相色谱（FID/MS）检测。对比不同的采样及处理方法,采样罐/低温浓缩一般与质谱联用,采样成本较高,灵敏度高,适用于环境空气中样品分析;固体吸附剂-溶剂解吸灵敏度较高,但容易造成二次污染;气袋采样-直接进样方便、简单,但灵敏度较低。可根据实际需要选择不同的采样及分析方法。     

浅谈HJ 836-2017《固定污染源废气低浓度颗粒物的测定 重量法》

对《固定污染源废气低浓度颗粒物的测定重量法》(HJ 836-2017)的适用范围、检出限、技术路线(采样前准备、现场采样要求和采样后样品称量计算)及质量控制等进行了解读。标准适用于排放浓度不大于50 mg/m~3的颗粒物检测;方法检出限为1 mg/m~3;通过改进采样头、增加采样设备预热功能、整体称量的方式等手段,减少采样及称重过程引入的误差;增加全程序空白及同步双样的质控要求保证检测过程的准确性。     

重要性采样方法与自由能计算

分子动力学模拟与自由能计算已经在化学、生物学与材料学等领域得到广泛的应用。然而,由于在传统分子动力学模拟的时间尺度内,体系很难跨越较高的自由能能垒,在相空间内的采样大大受限,采样困难使自由能计算难以收敛。增强采样是解决这一问题的有效途径,重要性采样方法就是其中一类。本文综述了四种广泛应用的重要性采样方法--伞状采样方法、metadynamics方法、自适应偏置力方法和温度加速分子动力学方法的原理和进展,其中重点概述了自适应偏置力方法的最新发展--扩展自适应偏置力方法和扩展广义自适应偏置力方法,并对这四种重要性采样方法的优缺点进行了比较。最后,讨论和展望了重要性采样与自由能计算方法面临的挑战和前景,并提出了对自适应偏置力方法可能的改进,如与加速分子动力学（aMD）或弦方法结合以提高在高维度空间中的采样效率。     

镀金石英砂吸附大气中痕量汞的直接测定方法

采用镀金石英砂来富集大气中的气态总汞,AMA(advanced m ercury analyzer)254测汞仪测定。结果表明,不同采样时间下的单级吸附管的吸附效率均在90%以上,采样40 m in时的相对标准偏差为5%左右。与巯基棉吸附及吸收液吸收方法的对比显示该方法具有吸收效果好、多次采样的精密度高、操作简便并且可以再生重复使用等优点。运用该法对上海徐家汇等几个地点的大气总汞进行了测定。     

副本交换分子动力学

副本交换分子动力学(REMD)是一种广泛应用于蛋白质功能性构象变化模拟及相应自由能计算的增强型采样算法。由于REMD理论严格且采样效率高,近年来备受关注,尤其是针对传统REMD方法的发展和优化,显著提高了REMD的采样效率,拓展了其应用范围。但是各种REMD新型方法的最佳适用范围也存在较大区别,使得如何选用合适的REMD方法成为实际应用的难题和挑战。因此,有必要对各种REMD方法及其应用进行阐述,深入比较各方法的优缺点及其实际应用体系。本综述从REMD的原理出发,回顾了近年来各类REMD方法的变形策略,以助于对REMD方法的理解、应用和继续改进。     

2,4-二硝基苯肼衍生-高效液相色谱测定大气细粒子中二羰基类化合物

以2,4-二硝基苯肼作为衍生化试剂,采用高效液相色谱法定量检测了大气细粒子(PM2.5)中二羰基类化合物。以乙二醛和甲基乙二醛为目标化合物,对二羰基类化合物采样条件(采集时间,流速等)、样品处理及分析条件进行了优化。研究表明,利用3mL衍生化溶液(含0.25mmol/LHCl和30μL饱和DNPH-乙腈溶液)和3mL乙腈可有效提取滤膜上的二羰基类化合物;本方法在滤膜采样12h内的采样及洗脱效果较好。利用此方法对上海市宝山区上海大学和崇明东平国家森林公园大气细粒子(PM2.5)中二羰基化合物进行了检测。     

分析化学中的采样及其质量控制

本文讨论了采样在分析化学中的地位及相关的问题,认为采样是分析过程的重要步骤之一,分析质量的控制在于试样质量的控制。采样必须依据研究目的而定,并通过评价系统协调试样类型、试样数目、试样尺度、采样位置和采样程序,以达到控制试样质量的目的。文献25篇。     

活体固相微萃取技术在动植物体内污染物分析中的应用

固相微萃取作为一种简便、快速、绿色的采样和样品前处理技术,近年来引起了广泛关注。在活体分析领域,基于相关萃取动力学理论的发展和新型活体采样探针的研制,固相微萃取技术逐步用于不同动植物体系中多种污染物的分析。本文概述了固相微萃取活体定量校正方法的开发、活体采样动力学过程的研究、新型活体采样探针的制备,以及活体固相微萃取方法在动植物组织中污染物快速检测及污染物富集和消除过程跟踪研究中的应用。此外,本文也对活体固相微萃取技术今后的发展方向和应用前景进行了展望。     

气相色谱法分析含硫恶臭物质综述

综述了含硫恶臭物质的气相色谱分析方法。详细介绍了目前分析含硫恶臭物质常用的采样及预处理方式、色谱柱和检测器,对不同的采样及预处理方式进行了比较。在预处理方面,可选择FTFE气袋、硅烷化苏玛罐采样,通过三级冷阱预浓缩后进样;或者采用Hayesep N、Tenax TA等吸附剂采样,热脱附进样。在分离方面,非极性柱、中极性柱可同时分离多种物质,应用范围较广;专用色谱柱有更好的分离效果。在检测方面,硫化学发光检测器(SCD)对含硫化合物有更高的选择性,线性关系好,检出限低,全二维气相色谱和飞行时间质谱联用具有更好的检测效果,但成本较高,操作复杂,难以推广。最后展望了未来的研究方向,为进一步优化分析方法提供参考。     

固定污染源废气硫酸雾采集及前处理优化研究

论文在对国内外文献调研基础上,通过大量实样测定对国标方法 HJ544-2009固定污染源废气硫酸雾的采集及前处理方法进行优化改进。该方法将采样过程改为在烟尘采样管后串联一支冲击式吸收瓶,此方法扩大了污染源适用范围,提高采样效率。该方法还将样品前处理过程改为超声波浸取法,省略了原国标方法加热、洗脱、过滤、定容等步骤;新方法还对滤筒材质、超声波浸出时间、浸出液等进行优化筛选,改进后的方法简便、准确、高效。     

Analysis of peak asymmetry in chromatography

The knowledge of the symmetry of chromatographic peaks is extremely important regarding the digital signal processing. The significant deviation of the peak shape from the symmetrical peak makes hardly possible the acquisition of chromatographic signal information, such as the retention time, the peak area, the peak width at half peak height, the peak overlapping, etc. In the literature one can find many methods for the determination of the asymmetry factor. For example it is suitable to calculate the skewness from the third central moment. However in case of noisy baseline the value of the skewness oscillates highly depending on the number of points used for the mathematical calculation. In this work a new method is presented for the determination peak shape asymmetry. We order mathematical function to the chromatographic peaks by fitting, and then symmetrical curve is generated with the same peak maximum position and height, the peak width is fitted. The difference of the two functions is constituted and areas of the data differences are calculated, which are really characteristics of the peak asymmetry. Correlation between the area of the difference signal and the asymmetry factor is established. The method was applied for different types of chromatographic peak shapes and the results were interpreted.     

Ultrahigh-resolution (1)H-(13)C HSQC spectra of metabolite mixtures using nonlinear sampling and forward maximum entropy reconstruction

To obtain a comprehensive assessment of metabolite levels from extracts of leukocytes, we have recorded ultrahigh-resolution 1H-13C HSQC NMR spectra of cell extracts, which exhibit spectral signatures of numerous small molecules. However, conventional acquisition of such spectra is time-consuming and hampers measurements on multiple samples, which would be needed for statistical analysis of metabolite concentrations. Here we show that the measurement time can be dramatically reduced without loss of spectral quality when using nonlinear sampling (NLS) and a new high-fidelity forward maximum-entropy (FM) reconstruction algorithm. This FM reconstruction conserves all measured time-domain data points and guesses the missing data points by an iterative process. This consists of discrete Fourier transformation of the sparse time-domain data set, computation of the spectral entropy, determination of a multidimensional entropy gradient, and calculation of new values for the missing time-domain data points with a conjugate gradient approach. Since this procedure does not alter measured data points, it reproduces signal intensities with high fidelity and does not suffer from a dynamic range problem. As an example we measured a natural abundance 1H-13C HSQC spectrum of metabolites from granulocyte cell extracts. We show that a high-resolution 1H-13C HSQC spectrum with 4k complex increments recorded linearly within 3.7 days can be reconstructed from one-seventh of the increments with nearly identical spectral appearance, indistinguishable signal intensities, and comparable or even lower root-mean-square (rms) and peak noise patterns measured in signal-free areas. Thus, this approach allows recording of ultrahigh resolution 1H-13C HSQC spectra in a fraction of the time needed for recording linearly sampled spectra.     

The relaxation field for the general case of electrolyte mixtures

The relaxation field for solutions of mixed electrolytes of any type is calculated. the calculation is based on the well-known treatment due to Fuoss-Onsager with the same distance parameter for all the ions in solution. A general conductance-continuity equation has been established and an improved iterative method of calculation, using Laplace transforms, is proposed. The relaxation-field results are derived to the second iteration in the perturbation method of integration.     

Sampling frequency,response times and embedded signal filtration in fast,high efficiency liquid chromatography: A tutorial

With increasingly efficient columns, eluite peaks are increasingly narrower. To take full advantage of this, choice of the detector response time and the data acquisition rate a.k.a. detector sampling frequency, have become increasingly important. In this work, we revisit the concept of data sampling from the theorem variously attributed to Whittaker, Nyquist, Kotelnikov, and Shannon. Focusing on time scales relevant to the current practice of high performance liquid chromatography (HPLC) and optical absorbance detection (the most commonly used method), even for very narrow simulated peaks Fourier transformation shows that theoretical minimum sampling frequency is still relatively low (<10 Hz). However, this consideration alone may not be adequate for real chromatograms when an appreciable amount of noise is present. Further, depending on the instrument, the manufacturer's choice of a particular data bunching/integration/response time condition may be integrally coupled to the sampling frequency. In any case, the exact nature of signal filtration often occurs in a manner neither transparent to nor controllable by the user. Using fast chromatography on a state-of-the-art column (38,000 plates), we evaluate the responses produced by different present generation instruments, each with their unique black box digital filters. We show that the common wisdom of sampling 20 points per peak can be inadequate for high efficiency columns and that the sampling frequency and response choices do affect the peak shape. If the sampling frequency is too low or response time is too large, the observed peak shapes will not remain as narrow as they really are – this is especially true for high efficiency and high speed separations. It is shown that both sampling frequency and digital filtering affect the retention time, noise amplitude, peak shape and width in a complex fashion. We show how a square-wave driven light emitting diode source can reveal the nature of the embedded filter. We discuss time uncertainties related to the choice of sampling frequency. Finally, we suggest steps to obtain optimum results from a given system.     

Boundary element solution of the linear Poisson-Boltzmann equation and a multipole method for the rapid calculation of forces on macromolecules in solution

The Poisson-Boltzmann equation is widely used to describe the electrostatic potential of molecules in an ionic solution that is treated as a continuous dielectric medium. The linearized form of this equation, applicable to many biologic macromolecules, may be solved using the boundary element method. A single-layer formulation of the boundary element method, which yields simpler integral equations than the direct formulations previously discussed in the literature, is given. It is shown that the electrostatic force and torque on a molecule may be calculated using its boundary element representation and also the polarization charge for two rigid molecules may be rapidly calculated using a noniterative scheme. An algorithm based on a fast adaptive multipole method is introduced to further increase the speed of the calculation. This method is particularly suited for Brownian dynamics or molecular dynamics simulations of large molecules, in which the electrostatic forces must be calculated for many different relative positions and orientations of the molecules. It has been implemented as a set of programs in C++, which are used to study the accuracy and speed of this method for two actin monomers.     

一种基于光谱分析的二元不完全重叠色谱峰的分离解析方法

基于二极管阵列检测器获得的色谱-光谱数据,建立了一种二元不完全重叠液相色谱峰的解析方法: 色谱数据经过去噪、归一化处理后,计算各时间点的光谱差异并进行系统聚类分析,提取特征光谱后,利用非负最小二乘法对色谱-光谱矩阵进行解析,得到基于特征光谱的流出曲线,进而得到分离后的色谱峰。将解析结果和纯标样的色谱峰进行比较,解析后的光谱图和纯标样的光谱图无显著差异,保留时间相差小于0.01 min。实验结果表明,该方法在二元不完全重叠液相色谱峰的解析方面能取得良好的效果。     

两点电位滴定法及其应用

提出了只需两组数据即可计算电位滴定计量点的电位滴定数据处理新方法－两点法，并在此理论基础上，提出了两点电位测定法。该法只需记录两次电极电位值和相应滴定剂体积，利用公式即可计算滴定化学计量点。详细讨论了各因素对方法准确度的影响，给出了衡量滴定进行程度的客观指标，为两点位置的选择提供了充分的理论依据。实验结果表明：该法操作方便，数据处理简单，精密度与准确度均较高，分析速度较经典电位滴定法有较大提高。     

Dependence of computed copolymer reactivity ratios on the calculation method. II. Effects of experimental design and error structure

Two calculation methods for estimating reactivity ratios, one method based on the differential Alfrey-Mayo equation and one based on the integrated form of this model, are compared with respect to precision and bias. Both methods are characterized by the use of information about the monomer feed composition only and are assumed to be valid up to high conversion. As only monomer feed composition has to be analyzed, several sampling designs are feasible. Two extreme designs can be distinguished. One consists of repetitive sampling of the initial and final monomer feed mixture, whereas the other consists of sequential sampling during the course of the reaction. The influence of both designs of the calculated r-values is investigated by means of simulation. In the present paper the second calculation method, based on the integrated form, is solved by a nonlinear least squares method considering errors in both variables. This method required additional information about the errorstructure of the data. As this information is mostly of approximate nature, the influence of misspecification of this error structure on the calculated r-values is also examined.     

Automatische digitale Meß- und Bestrahlungsanlage zur kinetischen Untersuchung von Photoreaktionen

A commercial scanning double-beam spectrophotometer [1] was extended at little cost to a combined measuring and irradiating device for the kinetic examination of photochemical reactions. The advantages in comparison to an earlier used single beam instrument [5] are: Simultaneous registration of the total absorption spectrum and digital acquisition of the absorbancy at selected wavelengths, a larger number of measuring points during reaction procedure, off-line data sampling, and shorter interruption periods of irradiation during measurement because of reduced data acquisition time. Two examples prove the high accuracy and the extended area of application.     

Optimisation of data handling and detection conditions for automated chromatographic assay software

Summary The principle of automated chromatographic peak detection and analysis software is summarized, and critical steps are systematically studied. As the only parameter to be entered is the acquisition frequency, evaluation of its effect on software performance is discussed. In the case of relatively noisy chromatograms, it is shown experimentally that numerous points per peak have to be taken, leading to quite fast computer acquisition procedures. The use of discrete Fourier transform filtration techniques can modify peak shapes and a comparative study evaluates the relative errors induced in the shapes and characteristics of the chromatographic profiles. Optimisation of filtering conditions is achieved and it is shown that for a filter position only 2% of the Nyquist frequency no deformation occurs in the chromatographic profile. Detection of the start and finish of chromatographic peaks is optimized according to a simple four step iterative procedure. In the case of simulations, the difference between the values used to simulate peaks and those calculated by the software are less than 1%.