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1.
极化效应指数与脂肪酯类化合物沸点的定量构效关系研究   总被引:1,自引:0,他引:1  
基于烷基极化效应指数(PEI)构建了有效碳原子数(NCeff)用于定量表示烷基碳链相对长度.用最佳子集回归方法建立了脂肪酯沸点与PEI,NCeff参数的定量构效关系模型,该模型对训练集计算值与实验值的相关系数R2为0.9958,标准偏差s为3.98 K,对测试集预测值与实验值的相关系数R2分别为:0.9958,标准偏差s为3.92 K,计算结果表明基于参数PEI和NCeff所建立的脂肪酯类化合物的沸点定量构效关系模型具有良好的预测能力.  相似文献   

2.
应用循环伏安法、差分脉冲伏安法、控制电位电解法等电化学方法和紫外光谱法研究了粉防己碱在玻碳电极上的电化学行为及其与DNA的相互作用,并对相关电化学动力学参数进行考察。结果表明,粉防己碱在玻碳电极上发生了受扩散控制的不可逆氧化反应,其在玻碳电极上的电子转移数为2、质子转移数为2、电荷转移系数为0.62。粉防己碱的峰电流随着DNA的加入而降低,且峰电位发生正移,表明粉防己碱与DNA通过嵌插方式相互作用生成复合物,同时计算了两者反应的结合数以及结合常数,结果显示粉防己碱和DNA以1∶1结合形成粉防己碱-DNA复合物,结合常数为4.27×103。  相似文献   

3.
本文介绍闲气相色谱法定性、定量测定工业直链烷基磺酸盐在浓磷酸介质中脱磺酸基后,用石油醚萃取释出的不同碳数烷基的含量,然后,根据烷基的平均相对分子量,分别加-SO_3Na基的值,从而计算出工业直链烷基磺酸盐的平均相对分子量的方法。该法快速、简易和准确。  相似文献   

4.
盛立彦  刘婷婷  李美华  潘洁  罗勇 《色谱》2017,35(8):875-880
为了实现气相色谱无标样定量分析,通过测定66种化合物的GC-FID相对响应因子,研究反推得到的有效碳数与物质结构间的规律,得到了烷、醇、醚类有效碳数的计算方案。使用该方案计算所得理论预测值与实验测定值的相关系数达到0.999 8(N=66),所有化合物预测值与实验值相对偏差都在±3%以内,其中57%的化合物预测值与实验值的相对偏差在±1%以内。将其应用于汽油样品中含氧化合物的测定,各组分的测定结果与使用传统内标法测得的结果相当。运用有效碳数法预测相对响应因子,可实现气相色谱无标样检测,其准确度不逊于传统内标法,而时间成本与经济成本大幅下降。  相似文献   

5.
王华静  傅尧  王晨  郭庆祥 《化学学报》2008,66(3):362-370
利用六种密度泛函理论方法(B3LYP, B3P86, MPW1K, TPSS1KCIS, X3LYP, BMK)对碳氯键离解能进行理论计算,结果发现几种新发展的密度泛函(DFT)方法用于碳氯键离解能的计算比传统的B3LYP有较大的改善,其中对能量估算相对准确的B3P86方法对碳氯键离解能的计算精度最高,对17个分子中碳氯键离解能计算的平均绝对偏差为6.58 kJ/mol。最后运用B3P86方法对一系列环境危害较大,但可通过光化学降解和生物降解的氯代有机物的碳氯键离解能值进行预测,并讨论了影响碳氯键离解能的结构性质关系。  相似文献   

6.
王福安  杨长生  王文昌 《色谱》1988,6(4):225-226
刘大壮等曾提出气相色谱中同系物的交点方程:式中V_g~0、T~0为同系物类别的特性常数,m与温度无关,取决于化合物和固定液性质的参数。对正烷烃,参数m与碳数n成直线关系:本文研究指出了参数m的物理含义及其计算。  相似文献   

7.
在气相色谱分析中,通常采用相对保留值和Kovats保留指数作为化学物质的定性参数。相对保留值在使用中受到参考标准不一致的限制而难于推广,况且柱温对相对保留值的影响很大,其重现性还受到待鉴定物与参考标准保留值差距大小的影响。只有在待鉴定物与参考标准的保留值差距不大时,相对保留值才可靠。根据碳数规律,同系物  相似文献   

8.
高效液相色谱/电喷雾质谱联用分析乙二醇硬脂酸酯   总被引:1,自引:0,他引:1  
乙二醇硬脂酸酯和乙二醇双硬酯酸酯是日化工业中常用的珠光剂,被广泛地应用在丝毛洗涤剂、液体洗涤剂和护发用品等领域,对提高产品的性能和外观起到了良好的作用。样品中单双酯的相对含量和碳数分布对其使用性能有较大的影响,会直接影响到产品的稳定性,外观等。乙二醇硬脂酸酯的测定常用化学分析方法,测定其皂化价,酸价等指标^[1],从而间接估计其在样品中的含量,但无法测定样品中单双酯的相对含量和碳数分布情况。用高效液相色谱法,使用正相硅胶柱和四氢呋喃流动相,可以实现乙二醇单硬脂酸酯和乙二醇双硬脂酸酯的分离,但由于乙二醇硬脂酸酯无紫外吸收,需要用到示差折光检测器,无法实施梯度洗脱优化分离,该方法只能按单双酯分离,不能按碳数分离。用高温毛细管柱也可以直接进行乙二醇硬脂酸酯的气相色谱分析^[2]。本研究应用非反相高效液相色谱法,以大气压电离质谱为其在线检测器,同时实现单双酯的分离和按碳数的分离。  相似文献   

9.
本工作用外加驰豫试剂及反转门控去偶方式对菜籽油和“营养”油进行了~(13)C-NMR谱的定量测定。在归属各峰基础上,认为该两油脂都以甘油酯形式存在。提出了①多烯类结合脂肪酸占烯类总量的摩尔分数P;②烯碳数与饱和碳数之比R;③包括同种油脂及不同油脂间的油脂分子各类功能团的相对含量的测定计算表达式。  相似文献   

10.
应用循环伏安法、差分脉冲伏安法、控制电位电解法等电化学方法和紫外光谱法研究了粉防己碱在玻碳电极上的电化学行为及其与DNA的相互作用,并对相关电化学动力学参数进行考察。结果表明,粉防己碱在玻碳电极上发生了受扩散控制的不可逆氧化反应,其在玻碳电极上的电子转移数为2、质子转移数为2、电荷转移系数为0.62。粉防己碱的峰电流随着DNA的加入而降低,且峰电位发生正移,表明粉防己碱与DNA通过嵌插方式相互作用生成复合物,同时计算了两者反应的结合数以及结合常数,结果显示粉防己碱和DNA以1∶1结合形成粉防己碱-DNA复合物,结合常数为4.27×103。  相似文献   

11.
醛、酮类腙衍生物校正因子的预测与测定   总被引:3,自引:0,他引:3  
利用2,4-二硝基苯肼(DNPH)与醛、酮类化合物反应生成稳定的衍生物2,4-二硝基苯腙,对所生成的DNPH衍生物溶液直接进行气相色谱分析;以苯为内标物,分别对6种醛、酮衍生物的校正因子进行了预测和回归,校正因子的实际测定值与理论预测值的最大相对误差不超过0.4%。实验说明对反应生成物直接进行校正因子测定的方法是可靠的,且方法操作简单;同时也说明使用理论计算方法预测醛、酮DNPH衍生物校正因子的可行性,为使用理论计算方法预测其它醛、酮DNPH衍生物的校正因子奠定了基础。  相似文献   

12.
A method is proposed for the quantitative estimation of the carbon ionization coefficient followed by the determination of its concentration in silicate glasses by secondary ion mass spectrometry (SIMS). The method is based on the calculation of the sputtering ratio of carbon from the surface of silicate glasses. The dependence of the ionization coefficient on the NBO/T parameter (ratio of the number of nonbridging oxygen atoms to the number tetrahedrally coordinated silicon and aluminum ions), corresponding to the structure and composition of the matrix, is shown. The dependences obtained are calibration graphs for the determination of the ionization coefficient and for the subsequent quantitative estimation of carbon in a silicate sample for a particular SIMS instrument and experimental conditions.  相似文献   

13.
Quantitative determination of the elemental composition of metals and other solids by glow discharge mass spectrometry requires a calibration factor for each element. In past work, these factors, called relative ion yields (RIYs), have been determined experimentally from the mass spectra of standards of certified composition. The RlYs of some elements were found to be over 10 times larger than the RIYs of other elements. In this study a simple calculation of the RIYs of the elements within the same sample is derived from a theoretical framework which takes into account the combined effects of sputtering and ionization. The ionization function involves the electron affinity and the first ionization potential of each element, plus two unknown parameters. By favorable selection of a temperature parameter and a chemical-potential parameter, the RIYs calculated by this method were found to agree satisfactorily with the experimental RlYs of former work. The temperature of 16,000 K (used in this work) corresponds to an average electron energy of ~ 2 eV.  相似文献   

14.
A membrane inlet mass spectrometer connected to a miniaturized reactor was applied for dynamic dissolved gas analysis. Cell samples were taken from 7 mL shake flask cultures of Corynebacterium glutamicum ATCC 13032, and transferred to the 12 mL miniaturized reactor. There, oxygen uptake and carbon dioxide and its mass isotopomer production rates were determined using a new experimental procedure and applying nonlinear model equations. A novel dynamic method for the calibration of the membrane inlet mass spectrometer using first-order dynamics was developed. To derive total dissolved concentration of all carbon dioxide species (C(T)) from dissolved carbon dioxide concentration ([CO(2)](aq)), the ratio of C(T) to [CO(2)](aq) was determined by nonlinear parameter estimation, whereas the mass transfer coefficient of CO(2) was determined by the Wilke-Chang correlation. Subsequently, the suitability of the model equations for respiration measurements was examined using residual analysis and the Jarque-Bera hypothesis test. The resulting residuals were found to be random with normal distribution, which proved the adequacy of the application of the model for cell respiration analysis. Hence, dynamic changes in respiration activities could be accurately analyzed using membrane inlet mass spectrometry with the novel calibration method.  相似文献   

15.
A quantitative method was developed for the determination of phosphatidylcholine (PC) species concentration using nanoflow LC-ESI-MS/MS. In this study, a calibration method is developed to determine the effect of PC carbon chain length on MS peak intensity. Using the multiple standard addition method, a relationship between the peak intensities of different PC species from nanoflow LC-MS and carbon chain length is established first using different injection amounts of PC standards. From this relationship, a calibration curve for each carbon chain length can be obtained for the concentration calculation. It was found that the MS peak area of PC species analyzed by nanoflow LC-MS linearly decreased with increased acyl carbon numbers, and that the effect of the degree of acyl chain unsaturation on MS peak intensity was minimized when the injection amount was maintained at less than 1 pmol. The method was applied for the quantitative calculation of 34 PC species from rat liver, which were identified from data-dependent MS/MS analysis during nanoflow LC separation.  相似文献   

16.
A study is presented of the factors affecting the calibration of the mass scale in time-of-flight secondary ion mass spectrometry (TOF-SIMS). At the present time, TOF-SIMS analysts using local calibration procedures achieve a rather poor relative mass accuracy of only 150 ppm for large molecules (647 u) whereas for smaller fragments of <200 u this figure only improves to 60 ppm. The instrumental stability is 1 ppm and better than 10 ppm is necessary for unique identification of species. The above experimental uncertainty can lead to unnecessary confusion where peaks are wrongly identified or peaks are ambiguously assigned. Here we study, in detail, the instrumental parameters of a popular single stage reflection TOF-SIMS instrument with ion trajectory calculations using SIMION. The effect of the ion kinetic energy, emission angle, and other instrumental operating parameters on the measured peak position are determined. This shows clearly why molecular and atomic ions have different relative peak positions and the need for an aperture to restrict ions at large emission angles. These data provide the basis for a coherent procedure for optimizing the settings for accurate mass calibration and rules by which calibrations for inorganics and organics may be incorporated. This leads to a new generic set of ions for mass calibration that improves the mass accuracy in our interlaboratory study by a factor of 5. A calibration protocol is developed, which gives a relative mass accuracy of better than 10 ppm for masses up to 140 u. The effects of extrapolation beyond the calibration range are discussed and a recommended procedure is given to ensure that accurate mass is achieved within a selectable uncertainty for large molecules. Additionally, we can alternatively operate our instrument in a regime with good energy discrimination (i.e., poor energy compensation) to study the fragmented energies of molecules. This leads to data that support previous concepts developed in G-SIMS.  相似文献   

17.
In this study, the method for determining the stable carbon isotope ratio value was validated. Measurement uncertainty of stable carbon isotope ratio value of whole honey and its extracted protein derived from repeatability, reference gas, reference standards and calibration curve was calculated by applying the “bottom-up” approach according to Eurachem/CITAC guide. The expanded uncertainties for all results ranged from 0.14 to 0.19 ‰, with most of them between 0.15 and 0.16 ‰ (the coverage factor k = 2, the level of confidence p is approximately 95 %). The percentage contribution of each source to the relative combined uncertainty was calculated. The data indicated that calibration curves have more contribution to the relative combined uncertainty than repeatability and reference standards. On the other hand, the measurement uncertainty of C-4 sugar content in honey was estimated. Based on these results, 58 honey samples, such as acacia, chaste, Northeast China black bee, flowers and jujube honey, have been gathered to determine the C-4 plant sugar content adulteration in honey by elemental analyzer with an isotope ratio mass spectrometer. It can be found that all honey samples were not adulterated by C-4 plant sugar.  相似文献   

18.
The confidence in an individual measurement is the most important factor when selecting the elemental formula candidates from the list of possible elemental compositions following an exact mass measurement. It is the single mass measurement capability rather than the averaged mass measurement potential of the mass spectrometer that is the critical factor when validating the exact mass measurements of small molecules. Here, an experimental protocol has been established to determine the frequency of exact mass measurement by Fourier transform ion cyclotron resonance mass spectrometry (FT-ICRMS) at known relative ion abundance ratios (RA). This in turn allows for statements about the confidence limit for any single exact mass measurement to be made. This is particularly crucial for a high throughput, automated environment where operator intervention is required to be minimal and repeat analyses are to be avoided. The relative ion abundance calculations are essential to determine the working ranges for specific sample ion abundances. Further, it has been shown that if the sample ion abundance is low, then the ion abundance range for the calibration file does not need to be exactly or closely matched, again benefiting the high throughput application.  相似文献   

19.
A new algorithm is proposed for x-ray fluorescence analysis by the standard background method using a modified universal equation common for all analytes. In the new version of the universal equation, complicating factors can be accounted for by introducing additional correcting members into the analytical parameter. The developed procedure allows the analyst to give up numerous constraint equations, simplify the calibration of spectrometers, and improve the rapidity of the analysis of multielement ores and products of their processing without a drop in the accuracy of the results.  相似文献   

20.
When an analyte can be chromatographed on a HPLC column using a suitable solvent, the diffusion coefficient of this analyte into the solvent can easily and accurately be determined, together with the calibration factor of the detector for this analyte. The experimental arrangement needed is based on a slight modification of the HPLC valve so that the analyte is introduced into the chromatographic column via a short diffusion column filled with the solvent. The new method is theoretically developed and the required mathematical relations have been derived. As an example, the diffusion coefficient of liquid benzene in chloroform, together with its calibration factor, are measured, under various experimental conditions, and the values found compare very well with that calculated by Wilke-Chang formula. Diffusivities and calibration factors of ions in aqueous liquid systems can also be determined by the new method.Dedicated to Professor Dr. Dr. h.c. mult. J. F. K. Huber on the occasion of his 70th birthday  相似文献   

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