用扩散和传质理论证明正常色谱峰为拖尾峰

将扩散和传质理论应用于色谱峰形的讨论,指出应该用浓度－时间分布公式描述色谱流出曲线,容易地证明了正常色谱峰为拖尾峰。     

柱后反应高效离子交换色谱法测定Cu(Ⅱ)、Zn(Ⅱ)、Ni(Ⅱ)、Co(Ⅱ)、Fe(Ⅱ)

目前,在无机离子交换色谱中,多使用电化学检测系统,今年我国也研制成了库仑检测器。我们应用了高效离子交换柱,实现了某些离子的分离;并选用了适当的螯合剂与流出组分进行了柱后螯合显色反应;用一般高效液相色谱仪常备的分光光度检测器,实现了某些无机离子的检测。这种方法既增强了检测某些离子的选择性,也提高了检测灵敏度。实践表明,用Partisil-10 SCX键合相离子交换柱进行分离,用水溶性二乙醇胺二硫代甲酸螯合剂为柱后反应试剂,检测波长为405毫微米,测得Cu(Ⅱ)、Zn(Ⅱ)、Ni(Ⅱ)、Co(Ⅱ)、Fe(Ⅱ)的检出限量为毫微克级。实验液相色谱仪Perkin-Elmer Series 3型,配有LC-65T紫外-可见分光光度检     

吸附剂性能和操作参数对流相色谱流出峰不对称性的影响

色谱流出峰的拖展现象普遍存在于制备和大型色谱分离过程中,它直接影响分离的产率和回收率。本文提出采用色谱流出峰形的不对称偏差度来表征色谱流出峰的拖尾程度,并基于液相色制备色谱分离过程ＦＡＤ－ＳＭＴ模型及吸附速率计算机模拟,定量分析了吸附剂性能和操作参数对色谱流出峰形不对称性的影响。     

吸附剂性能和操作参数对液相色谱流出峰不对称性的影响

色谱流出峰的拖尾现象普遍存在于制备和大型色谱分离过程中,它直接影响分离的产率和回收率．本文提出采用色谱流出峰形的不对称偏差度来表征色谱流出峰的拖尾程度;并基于液相制备色谱分离过程FAD－SMT模型及吸附速率理论,通过计算机模拟,定量分析了吸附剂性能和操作参数对色谱流出峰形不对称性的影响。结果表明：不仅是吸附剂的热力学和动力学性能（包括吸附相平衡关系、液固两相间的传质阻力）;而且柱的设计和吸附剂的装填状况（包括轴向扩散系数）,以及色谱分离的操作条件（进料时间、浓度和流速等）都直接影响色谱流出峰形的不对称性。随着吸附相平衡等温线的非线性程度增大,或者总传质系数的减小,色谱流出峰形的不对称偏差度明显增大;吸附剂吸附容量的减小也将引起色谱流出峰形的不对称偏差度的增加;色谱流出峰形的不对称偏差度与进科体积、浓度和流体线速,以及轴向扩散系数的增大成正比。     

油品族组成的详细分析和燃油中芳烃的分析

用毛细管液相色谱-毛细管气相色谱联用方法详细分析了航空煤油、各种柴油、润滑油、抽出油和塔底油的族组成。在毛细管液相色谱上分离得到的单环、双环、三环、四环和稠环芳烃族,经过多位存储接口后,顺序进入毛细管气相色谱,通过毛细管气相色谱对每个族组分作详细分析及定量。用单检测器的二维毛细管气相色谱切割-反吹方法定性定量分析汽油、航空煤油中的各种芳烃,从第一维柱流出的组分和第二维柱流出的组分都先后进入同一氢火焰离子化检测器中,因此能用质量校正响应因子归一化方法准确定量分析而不需要标准样。用上述技术分析实际样品,证明了     

对虾中氯霉素残留的分析方法研究

用液相色谱-质谱法定量检测对虾中微量的氯霉素残留。采用乙酸乙酯超声提取对虾组织中的氯霉素残留,以甲醇为流动相,选择m／x321／152为氯霉素的检测离子对,用多反应监测(MRM)技术测定。氯霉素流出液相色谱的时间在1．5min以内;线性范围是0．28-28．0μg／L;线性相关系数为0．99991。对虾中氯霉素的定量检测下限是0．07μg／kg,平均回收率在89％以上。该方法快速、灵敏,定量范围宽,检验结果准确可靠,应用性强。     

塔板理论色谱流出曲线性质的研究

塔板理论是色谱动力学理论的重要部分。本文采用数学方法把塔板理论色谱流出曲线从离散函数形式变换为连续函数形式。在此基础上运用计算机进一步研究了塔板理论色谱流出曲线的性质。     

拖尾峰的半峰宽

实际色谱流出曲线大多是接近高斯分布的不对称拖尾峰,许多作者用指数卷积的高斯分布函数来描述,     

高压液体色谱中的有机氮选择性检测器

高压液体色谱中检测器是有待研究的薄弱环节,至今缺少像气相色谱中火焰离子化那样高灵敏度和选择性的检测器。 D.H.Fine最近报导了一种用于高压液体色谱的有机氮选择性检测器—热氮分析器(TNA)。其原理是从色谱柱流出的液体进入检测器喷口与氧混合,在约     

色谱流出曲线方程的讨论

色谱流出曲线方程的讨论周申范（南京理工大学化工学院２１００９４）１引言由塔板理论导出的色谱流出曲线方程式是色谱理论的基础。它以简单而优雅的形式指出了有关一个柱内色谱峰分离的定性和定量机理。尽管它有某些不足，但由于它能很好地解释流出曲线的形状、浓度极大...     

Organic quantitative ultramicroanalysis by pyrolysis,and diffusion of hydrogen through quartz,and by carbonization

Summary Quantitative ultramicro determination of hydrogen, based on the diffusion of hydrogen set free by complete thermal destruction of an organic compound through the wall of a silica glass flask, in which the sample is sealed, has been achieved. Both the percentage of hydrogen and of the molecule residue can be determined. By crushing the flask and weighing, after complete diffusion of hydrogen, the determination of carbon and oxygen ought to be possible.

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Zusammenfassung Auf der Grundlage der Pyrolyse einer organischen Substanz und der Diffusion des dabei freigesetzten Wasserstoffs wurde eine Ultramikromethode zur Bestimmung dieses Elementes ausgearbeitet. Die Probe wird in ein Quarzkölbchen eingeschmolzen, durch dessen Wandung der Wasserstoff diffundiert. Sowohl die Bestimmung des Wasserstoffgehaltes wie des Molekülrestes ist möglich. Nach vollständiger Diffusion des Wasserstoffes und Öffnen des Kölbchens sollten sich Kohlenstoff- und Sauerstoffgehalt durch Wägung bestimmen lassen.

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Résumé On a réalisé la détermination quantitative de l'hydrogène à l'échelle ultramicro, en se fondant sur la diffusion de l'hydrogène mis en liberté par destruction thermique complète d'un composé organique à travers la paroi d'un récipient en silice contenant l'échantillon scellé. On peut doser à la fois les pourcentages de l'hydrogène et du résidu moléculaire. On a pu doser le carbone et l'oxygène en cassant le récipient et en le pesant, après la diffusion complète de l'hydrogène.

     

Determination of Lead, Cadmium, and Mercury by On-Line Enrichment Followed by RP-HPLC

A new method for the simultaneous determination of lead, cadmium, and mercury ions as metal tetra-(4-chlorophenyl)-porphyrin (T₄CPP) chelates was developed using reversed-phase-high performance liquid chromatography (RP-HPLC) and combined with on-line enrichment technique. When the Hg-T₄CPP, Pb-T₄CPP, and Cd-T₄CPP chelates were injected into the injector and sent to the enrichment column with 0.05 mol/L of pH = 10 pyrrolidine-acetic acid buffer solutions (containing 10% of THF) as mobile phase, they were absorbed onto the tip of the enrichment column. By switching the six ports switching valve, the retained chelates can be back-flushed by mobile phase and travel towards the analytical column. With 0.05 mol/L of pH = 10 pyrrolidine-acetic acid buffer solution (containing 10% of THF) and tetrahydrofuran (THF) (containing 0.05 mol/L pH = 10.0 pyrrolidine-acetic acid buffer salt) gradient elution as mobile phase, the separation of chelates on the analytical column was satisfactory. The linearity ranges are 0.01 ± 120 g/L for each metal chelate. The detection limits (S/N = 3) of lead, cadmium, and mercury are 2.0, 1.5, and 2.0 ng/L, respectively. This method was applied to the determination of the g/L level of lead, cadmium, and mercury ions in a water sample with good results.     

Vertical and nonvertical participation by sulfur,selenium, and tellurium

The mechanism of stabilization of positive charge on carbon by sulfur, selenium, or tellurium at the beta-position has been investigated kinetically, by measurement of rate enhancements, and structurally, by variation of the bond strength to the leaving group. Stabilization can occur either nonvertically with formation of a bridged intermediate or vertically through hyperconjugation within an open carbocation. We observed large rate enhancements (10(5) for S, 10(6) for Se) in 97% aqueous trifluoroethanol with trifluoroacetate as the leaving group. These enhancements are consistent with either mechanism. Product structures also are consistent with either mechanism. Nine crystal structures revealed that the bond to the leaving group (C-O) is lengthened by the presence of S or Se at the beta-position, in proportion to the basicity of the leaving group. This lengthening is not accompanied by angle distortions expected for the bridging mechanism. The crystallographic data support vertical (hyperconjugative) character along the reaction coordinate, more so for selenium than sulfur.     

Determination of sulphide, polysulphide, thiocarbonates and sulphur by extraction with tributyltin hydroxide, and of thiosulphate by hydrogenation

The methods presented involve the separation of sulphur compounds by means of a hexane solution of tributyltin hydroxide (TBT), followed by titration with o-hydroxymercuribenzoic acid in the presence of dithizone as indicator. Free sulphide is selectively extracted from strongly alkaline solution, whereas the polysulphides and thiocarbonates are extracted at pH 9-10. The polysulphide and thiocarbonate extracts decompose to form TBT-sulphide, sulphur and carbon disulphide. Treatment with sulphite, stannate(II), copper, vinyl cyanide and ethylenediamine, and hydrogenation with zinc and hydrobromic acid have been applied in the course of the analysis. The sulphur is determined by its attack on copper to form copper(I) sulphide which is subsequently dissolved in aqueous potassium cyanide solution and the sulphide separated by extraction.     

Bacteria and the Biodegradation of Chemicals Achieved Naturally,by Combination,or by Construction

The natural potential of bacteria for the biological degradation of synthetic compounds is greater than is commonly supposed and extends to many heteroarenes and even some chloroarenes. An increase in the number of substituents on the aromatic ring or a certain substitution pattern is what confers xenobiotic character to a compound. In addition, when enzymes with low substrate specificity encounter foreign compounds with random variations, products with very strong xenobiotic character often result. In this case, changing the conditions or introducing a cooperation between several different types of bacteria can be used to degrade these compounds. Finally, mineralization, the complete breakdown of organic substances into carbon dioxide and inorganic salts, of xenobiotics previously regarded as persistent can be achieved by taking advantage of natural or induced gene transfer to construct hybrid degradative pathways. After an introduction to the world of bacteria and their place in Nature, we will describe their natural potential for biodegradation with reference to aliphatic and aromatic hydrocarbons. The discussion will then turn to the types of the substituents that confer xenobiotic properties to compounds and how these compounds are degraded despite their xenobiotic character.     

Assay of d-cycloserine by chloramine-B,bromamine-T,and bromamine-B

The reaction between d-cycloserine (DCS) and aromatic N-haloamines proceeds quantitatively over a wide range of experimental conditions. Simple titrimetric procedures for the assay of DCS are described. Oxidation of DCS involves an eight-electron change and the oxidation products are identified. The methods can be used for the assay of the antibiotic in medicinal preparations as well as for calculating the number of ligand molecules present in metal complexes of DCS.     

Oral malodor,assessed by closed-loop,gas chromatography,and ion-trap technology

A method is described for the analysis of volatile organic compounds in saliva and tongue coating samples. The techniue is based on an off-line preconcentration step by means of a closed-loop trapping system followed by gas chromatography-ion trap detection. With the closed-loop technique, the volatile organic compounds(VOCs) are released from the matrix and trapped on an adsorbent without interference of water. The VOCs are released from the adsorbent into the gas chromatograph by thermdesorption. After separation, identification of the compounds is performed by ion trap technology. By this technique 82 compounds could be demonstrated in saliva and tongue coating samples. The technique is also used to demonstrate the formation of volatile bacterial fermentation compounds when a protein substrate is added to tongue coating samples. It is considered a very promising tool in further research on oral malodor.