气相色谱用氦直流等离子体离子化检测器的研究

报道三种不同类型的气相色谱用氦直流等离子体离子化检测器。以氦气为载气和工作气体, 白金电极为放电电极, 通过测量检测器的工作参数, 考察了检测器对H2, O2, Ar, N2, CH4, CO, CO2等永久气体的响应特性及分析性能, 并应用于实际样品分析。对检测器的离子化机理进行了研究和探讨。     

新型色谱用微波等离子体离子化检测器的研究

自1965年McCormark提出微波等离子体应用于气相色谱法以来,人们相继研制出多种类型色谱用微波等离子体检测器,并在环保、医药、卫生等部门得到应用。在近几年研究工作的基础上,本文提出了我们新近研制的一种色谱用微波等离子体离子化检测器(MPID),并对检测器的一些分析特性进行了考察。 MPID的结构和工作原理 微波等离子体离子化检测器是我们自己设计和加工组装的,结构示意图见图1。     

气相色谱-微波等离子体炬双检测器及其气相色谱的响应特性

提出并建立了气相色谱-微波等离子体炬(MPT)原子发射光谱和离子化双检测器系统. 以Ar气作为等离子体工作气体, O2气作为等离子体屏蔽气体, 同时获得了被测组分的原子发射和离子化信息, 并对不同种类有机化合物的相对响应系数及检出限进行了测定.     

微波诱导等离子体离子化检测器的研究——气相色谱法同时测定甲醇和水

本文采用带自制的微波诱导等离子体离子化检测(GC-MIPID)的气相色谱,以氩气为载气和工作气体,对甲醇和水的同时测定进行了详细研究。方法灵敏度优于氢火焰离子化检测器和热导池检测器,并且解决了用单一检测器难以同时测定甲醇和水的问题。方法已用于乙醇中甲醇和水的测定。文中还对MIPID的离子化机理作了初步的探讨。     

新型光离子化检测器

近几年来,光离子化检测器(Photoionization Detector,简称PID)的性能不断改进和完善,又为气相色谱在化学、生物学、医学、环境保护以及其它科学技术领域的应用,提供了新的、有效的检测手段。在1960年,Lovelock曾发表关于离子化检测器的论述,除氢火焰离子化检测器、截面积离子化检测器、电子捕获检测器之外,也提出了光离子化检测器(PID)。离子化检测器的基本原理,都是致使物质离子化,测定形成的离子流,进行色谱检出和定量测定。各种离子化检测器的离子化途径,则是互不相同的。在PID中,使用紫外光的辐射能,进行样品组份的激发电离,收集、放大和测定所形成的离子流,进行气相色谱的定性和定量。     

常压微波等离子体光离子化检测器的性能考察

一种新型的常压微波等离子体光离子化检测器(简称PID)已研制成功。这是一种稳定性好,灵敏度高,线性范围较宽的气相色谱检测器。此检测器的最大优点是 在常压下操作,用气量小(放电气体一般在5—20毫升/分),可改变等离子体的种类和控制光强度,以适应不同电离能的样品分析。本检测器对C_6H_6的敏感度为1.6×10~(-11)克/秒,对CS_2为1.8×10~(-11)克/秒,对苯的线性范围大于10~4。     

近期微型色谱硬件研究亮点

1微机电谐振气相色谱检测器 2高灵敏表面离子化气相色谱检测器 3微型化低功耗的二维气相色谱聚焦调制器 4阵列微柱体式芯片液相色谱柱     

用于气相色谱的微波等离子体原子发射光谱检测器的发展

分别介绍和评价了用于气相色谱的微波诱导等离子体、电容耦合微波等离子体和微波等离子体炬等3种微波等离子体原子发射光谱检测器的发展、应用以及局限性。对用于气相色谱的微波等离子体原子发射光谱检测器的发展作了展望。     

微波诱导等离子体离子化检测器响应特性的研究

微波诱导等离子体可在低功率和低工作气体流速下稳定地工作,已成功地应用于气相色谱检测器~[1～3].本文在文献~[4,5]工作的基础上,对MIPID的工作参数及其响应特性进行了研究,并初步探讨了样品的离子化机理.     

微波诱导等离子体离子化检测器的研究：气相色谱法同时测定甲醇…

本文采用带自制的微波诱导等离子体离子化检测（ＧＣ－ＭＩＰＩＤ）的气相色谱，以氩气为载气和工作气体，对甲醇和水的同时测定进行了详细研究。方法灵敏度优于氢火焰离子在和热导池检测器，并且解决了用单一检测器难以同时测定甲醇和水的问题。方法已用于乙醇中甲醇和水的测定。文中还对ＭＩＰＩＤ的离子化机理作了初步的探讨。     

Spatially resolved spectroscopic measurements of a dielectric barrier discharge plasma jet applicable for soft ionization

An atmospheric pressure microplasma ionization source based on a dielectric barrier discharge with a helium plasma cone outside the electrode region has been developed for liquid chromatography/mass spectrometry and as ionization source for ion mobility spectrometry. It turned out that dielectric barrier discharge ionization could be regarded as a soft ionization technique characterized by only minor fragmentation similar to atmospheric pressure chemical ionization (APCI). Mainly protonated molecules were detected. In order to characterize the soft ionization mechanism spatially resolved optical emission spectrometry (OES) measurements were performed on plasma jets burning either in He or in Ar. Besides to spatial intensity distributions of noble gas spectral lines, in both cases a special attention was paid to lines of N₂⁺ and N₂. The obtained mapping of the plasma jet shows very different number density distributions of relevant excited species. In the case of helium plasma jet, strong N₂⁺ lines were observed. In contrast to that, the intensities of N₂ lines in Ar were below the present detection limit. The positions of N₂⁺ and N₂ distribution maxima in helium indicate the regions where the highest efficiency of the water ionization and the protonation process is expected.     

氢气的分析方法研究

介绍了低纯度氢气和高纯度氢气的不同分析检测方法。对于纯度小于99.99%的氢气,其分析方法主要有爆炸法、吸收法、膜分离法和气相色谱法;对于纯度大于99.99%的氢气,其分析方法主要有变温浓缩的热导池气相色谱法、配有光电离子化检测器(DID)的气相色谱法和色谱-质谱联用法。     

Plasma diagnostics of an analytical Grimm-type glow discharge in argon and in neon: Langmuir probe and optical emission spectrometry measurements

Comparative investigations were performed on a Grimm-type glow discharge source by Langmuir probe measurements and by optical emission spectrometry. The Langmuir probe measurements yielded electron temperatures and number densities of electrons, whereas the optical emission spectrometry measurements resulted in data for excitation and ionization temperatures of different species. The results confirm that there is no local thermal equilibrium in the discharge plasma. The operating conditions of the glow discharge source and also the working gas and the cathode material were varied to investigate their influence on the plasma parameters. The outcome of the plasma diagnostics will be used to improve the modelling of relevant excitation and ionization processes by computer simulation. The major physical processes in the low pressure glow discharge plasma should be better understood if the analytical capability of this spectrochemical excitation and ionization source has to be further enhanced.     

Chromatographic analysis of blood lipids. Comparison between gas chromatography and thin-layer chromatography with flame ionization detection

Intact human blood plasma lipids of different composition were analyzed by gas chromatography and thin-layer chromatography with flame ionization detection. The reproducibility of the results obtained by gas and thin-layer chromatography was compared. The main advantages and disadvantages of both methods for lipid analysis are discussed. Generally, the variability of the results measured by thin-layer chromatography in series and from day to day was greater than that obtained by gas chromatography.     

Spectroscopic characterization of a microplasma used as ionization source for ion mobility spectrometry

We report a miniaturized excitation source for soft ionization of molecules based on a dielectric barrier discharge. An atmospheric plasma is established at the end of a 500 μm diameter capillary using He as buffer gas. The plasma jet which comes out of the capillary is dependent on the gas flow rate. The mechanism of the production of N₂⁺ outside the capillary, which is relevant for the protonation of molecules and sustains the production of primary ions, is investigated by spatially resolved spectroscopic measurements throughout the plasma. Possible application of such miniaturized plasmas is the ionization of gaseous compounds under atmospheric pressure as an alternative to traditional APCI (atmospheric pressure chemical ionization). The miniaturized plasma was applied as ionization source for ion mobility spectrometry where the common sources are radioactive, thus limiting the place of installation. First measurements of gaseous compounds with such a plasma ion mobility spectrometer with promising results showed detection limits comparable or even better than those obtained using common radioactive ionization sources.     

Analysis of amino acids in brain and plasma samples by sensitive gas chromatography-mass spectrometry

Gas chromatography-mass spectrometry-selected-ion monitoring provided a simple and sensitive method for analyzing amino acids in plasma and brain samples. Although the sensitivities of chemical ionization and electron-impact ionization were similar chemical ionization produced higher-mass ions, which might increase the selectivity of the assay. Both chemical and electron-impact ionization distinguished the natural amino acids from the 15N-labelled amino acids. The recovery of amino acids from plasma and brain samples was ca. 75%. The amino acid levels determined by gas chromatography-mass spectrometry were comparable with the amino acid levels determined by high-performance liquid chromatography or amino acid analyzer.     

Quantification of 5-fluoro-2'-deoxyuridine in plasma by gas chromatography and negative-ion chemical ionization mass spectrometry.

A sensitive and specific method using gas chromatography and negative-ion chemical ionization mass spectrometry is described for the determination of 5-fluoro-2'-deoxyuridine (FdUrd) in plasma. The method is based on the formation of the pentafluoropropionyl derivative of FdUrd and of its stable isotope as internal standard after sample clean-up by solid-phase extraction and purification by high-performance liquid chromatography. Quantification in plasma was possible down to 300 pg/ml. The method was applied to the analysis of plasma levels of FdUrd in mice and dogs.     

Multi-element selective radio frequency plasma detector for capillary gas chromatography

A radio frequency plasma detector for element specific detection in gas chromatography is described. The detector is comprised of a radio frequency (300 kHz) discharge between electrodes in helium, and utilizes a low-resolution emission spectrometer to monitor selected spectral emission lines produced when the helium discharge decomposes and excites the atomic constituents in the chromatographic column effluent. The spectrometer is tuned to an atomic emission line in the near-infrared portion of the spectrum, and the emission intensity from the discharge region of a selected line is used to monitor the concentration of the element producing that line. Acceptable detector sensitivity was achieved by the use of a high-throughput optical system. Selectivity was achieved by a combination of correct line selection, plasma and carrier gas purification, and plasma gas doping.