气相色谱-微波等离子体炬原子发射光谱检测器及其响应特性的研究

报道了一种气相色谱用微波等离子体炬原子发射光谱检测器(GC-MPT-AED),以氩气为载气和等离子体工作气体,氧气为清洗气和屏蔽气,研究了MPT-AED对有机化合物中碳元素的响应特性,探讨了氧气作为GC-MPT-AED屏蔽气对碳元素检测性能的影响.     

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.     

气相色谱用微波等离子体炬原子发射光谱检测器的Cl,Br,I响应特性的研究

 将微波等离子体炬原子发射光谱检测器(MPT-AED)用作气相色谱检测器,采用氩气作为工作气、载气和尾吹气,优化了气体流量参数;为了防止被测物质在管壁上的沉积,考察了氧气作为气相色谱-微波等离子体炬-原子发射光谱检测器(GC-MPT-AED)清洗气时对Cl,Br,I3种元素发射信号的影响。为了考察检测器的分析性能,研究了GC-MPT-AED对有机化合物中Cl,Br,I3种元素的检出限、线性范围、精密度及其响应特性,并将其结果与气相色谱-电感耦合等离子体-原子发射光谱检测器(GC-ICP-AED)的结果作了比较,结果表明该仪器对Cl,Br的检测能力优于GC-ICP-AED的结果,线性范围与GC-IC     

氧-火焰离子化检测器的研制及应用

本文介绍选择测定复杂有机混合物中各含氧化合物的氧-火焰离子化(O-FID)检测器,该仪器是专门对氧响应的O-FID检测器,还报道了在O-FID检测器上对含氧化合物的定量校正工作。     

Selective determination of organofluorine compounds by capillary column gas chromatography with an atmospheric pressure helium microwave-induced plasma detector

Fluorinated analogs of compounds typical of those found in metabolic and other biological studies are detected with high selectivity using a gas chromatograph/microwave-induced plasma detector (GC-MIPD), which permits fluorine-selective detection by monitoring the emission at 685.6 nm. Using the described atmospheric pressure helium-sustained plasma detector, the minimum detectable level, fluorine selectivity (relative to carbon), and linear dynamic range of this GC-MIPD system were determined to be 4.8 pg-F/s, 1060, and 5000, respectively. The utility of this GC-MIPD system for the selective detection of organofluorine compounds is demonstrated by its application in the analysis of the metabolic fate of a fluorinated substrate administered to a mixture of wheat germ phosphatase and potato apyrase, as well as by analysis of synthetic mixtures.     

Metal selective flame ionization detection after supercritical fluid chromatography

This work describes the construction and operation of a flame ionization detector for the selective detection of metal-containing compounds after capillary supercritical fluid chromatography. Using optimal conditions for achieving metal sensitive flame ionization responses which have been established for the detector after capillary gas chromatography, initial evaluation of the detector after SFC proved promising. Like the carbon sensitive FID, it appears that the metal sensitive FID is compatible with SFC when pure carbon dioxide is used as the mobile phase. Response characteristics were found to be similar to those observed when the detector is used in gas chromatography.     

Investigating the performance characteristics of the barrier discharge ionization detector and comparison to the flame ionization detector for the gas chromatographic analysis of volatile and semivolatile organic compounds

Abstract

The response behavior and performance characteristics of the recently introduced barrier discharge ionization detector (BID) for gas chromatography (GC-BID) were investigated by analyzing different classes of organic compounds such as alcohols, alkanes, cycloaliphatic compounds, polycyclic aromatic hydrocarbons (PAHs), and others. The results obtained by GC-BID were compared with those of gas chromatography with flame ionization detection (GC-FID), aiming to demonstrate the particular merits of the new BID detector over the well-established FID. The response of the BID not only was found to be strongly dependent on the detector settings, but also shows a high dependence on the analyte class and the individual analyte. The sensitivity of the BID detector compared to the FID was higher by a factor of ca. 4 on average when considering all compounds analyzed. The relative standard deviation (RSD) was better than 5% for the majority of the cases. The BID detector showed better precision (lower RSD) in comparison with the FID for the investigated compounds. Linear calibrations were obtained for the analytes over more than four orders of magnitude with coefficients of determination typically higher than 0.999 and the limits of detection varied from 0.04 to 1.48?ng/s for the GC-BID.     

Gas chromatographic determination of organolead compounds with an alternating current plasma detector

The performance of the gas chromatography/alternating current plasma detector as a selective detector for organolead compounds is investigated. The helium make-up flow rate and the spatial position from which the lead emission is viewed, have an effect on the detector response. The detection limit for tetrabutyl lead was established as 130 pg/s and the lead selectivity ratio was found to exceed 13,800. Some applications of organolead determination in complex matrices were also studied in order to demonstrate the selectivity and sensitivity of the alternating current plasma detector.     

The Use of the Helium Ionization Detector for Gas Chromatographic Monitoring of Trace Atmospheric Components

Two different gas chromatographic detectors, the helium ionization detector (HID) and the more commonly used flame ionization detector (FID), were used in parallel to compare their responses to a number of organic compounds. Atmospherically important oxygenated species were analyzed, as well as hydrocarbons and chlorinated and sulfur containing organics. The HID exhibited the better response to all compounds investigated, most notably to formaldehyde and higher oxygenates. A gas chromatographic system was developed to trap and analyze atmospheric organic compounds with HID detection. This required careful choice of the adsorbent material and removal of inorganic components (namely nitrogen and oxygen) before analysis. Real air samples were then taken and analyzed qualitatively for a range of olefinic and aromatic compounds.     

Preparation and application of cryptand-coated piezoelectric crystal gas-chromatographic detector

A re-usable and sensitive cryptand-22-coated quartz-crystal membrane piezoelectric sensor with a homemade computer interface for signal acquisition and data processing was prepared and applied as a gas-chromatographic (GC) detector for various organic molecules. The oscillating frequency of the quartz crystal decreased due to the adsorption of organic molecules on cryptand-22. Effects of functional group, molar mass, steric hindrance and polarity of organic molecules on frequency responses of the cryptand-coated piezoelectric crystal detector were investigated. The cryptand-coated piezoelectric crystal GC detector had demonstrated high sensitivity for various polar organic molecules and good reproducibility when re-used. The frequency responses of the cryptand-coated crystal for various molecules were in the following order: carboxylic acids (RCOOH)primary amines (R-NH₂)>alcohols (ROH)>secondary amines (R₂NH)>tertiary amines (R₃N)>ketones. More polar molecules exhibited better frequency responses. The effect of temperature and amount of coating on the frequency responses of cryptand-coated crystal GC detector were also investigated. The cryptand-coated piezoelectric crystal GC detector compared well with the commercial thermal conductivity detector (TCD).     

Element Specific GC-Detection by Plasma Atomic Emission Spectroscopy—A Powerful Tool in Environmental Analysis

Abstract

A new Plasma Emission Detector (FED) to be used in gas chromatography has been developed, consisting of a capacitively coupled helium plasma operating at 200 W and 27 MHz and a poly-chromator system. Elements such as H, C, N, O, S, F, Cl, Br and I can be simultaneously detected, giving way to new possibilities of measuring organic environmental pollutants.

1. Non-separated compounds can be easily measured with the FED, as long as the compounds contain different hetero-elements.

2. The calibration for a complex system as for example the chlorinated HC's demands only for a single standard.

3. The simultaneous detection of all elements of a separated compound allows the calculation of the total molecular formula.

The detection limits for different elements lie between 50 and 200 pg/sec at a signal to noise ratio of 3 to 1.     

Characterization of PVC BY SEC. II. One Shot Chromatography of the Organic Components of PVC Compounds

Abstract

1,2,4-Trichlorobenzene at 90°C proved to be a universal solvent for the common organic components of PVC compounds except crosslinked impact modifiers. Size exclusion chromatography was carried out with 8 different components, with a PVC-U compound and plate out formed during its extrusion using both RI and IR detection. In the RI detector PVC shows a very low detector response. It is therefore possible to analyze the whole organic fraction of the compound without prior precipitation of PVC. Using RI/IR double detection, an “one shot” analysis of the PVC matrix and of all the soluble additives can be accomplished.     

方波激发非接触式电导检测器信噪比的影响因素研究

研制了用于毛细管电泳的方波激发非接触式电导检测器(CCD)并详细考查了对检测器信噪比影响较大的几个重要因素,包括激发频率和运算放大器、基线分压电路和A/D转换器、数字低通滤波;以及常见缓冲体系2-(N-吗啡啉)-乙磺酸/组氨酸(MES/His)体系中电解质浓度,添加剂十六烷基三甲基溴化铵(CTAB)对金属离子的检出信号的影响。所得的结果对于该类检测器的设计和优化具有参考价值。     

Chlorine-Selective Detection in Supercritical Fluid Chromatography using a Coulson Electrolytic Conductivity Detector

Abstract

A Coulson electrolytic conductivity detector has been coupled successfully to a supercritical fluid chromatograph, providing chlorine-selective detection. This involves minimal modification of the detector and no modification of the SFC or its operation. The general operating parameters of the SFC/CECD system were established by direct injection of three probe compounds: chlordane, γ-lindane, and hexachlorobenzene. Next, the SFC separation of a test mixture containing phenol, γ-lindane, and several chlorinated phenols and related compounds was optimized using UV-Vis and FID detection. The mixture was then separated using the same chromatographic method but with the CECD in line with the UV-Vis detector. The response of the CECD was linear and selective for chlorinated compounds. Limits of detection for the test mixture by CECD ranged from 80 – 250 ng/μL, corresponding to approximately 14 – 44 ng of chlorine on column, and were dependent on chromatographic conditions, but independent of analyte structure.     

High temperature (70°C) size exclusion chromatography of petroleum waxes with RI and FID detection

Molecular weight distribution of solid petroleum waxes is a key parameter for the general characterization of these materials. Particular interest concerns extremely large components, typically present in oil distillation residua, and solid deposits found in oil production facilities. Molecular weight distributions of oil waxes were determined in this work by high temperature size exclusion chromatography. Separations were carried out with two different eluents, namely toluene and ortho-dichlorobenzene and two detection systems, these being a differential refractive index and a flame ionization detector. Toluene proved to be the best choice when combined with flame ionization detection. Better uniformity of response was the greatest advantage achieved by this approach. The experimental set up permitted analysis of samples containing molecules with up to 138 carbon atoms. Burning properties of very large molecules, isomerism affecting calibration, and signal asymmetry when flame ionization detection was adopted were three issues still requiring additional efforts to understand and to improve analysis accuracy.     

Development of an Atmospheric Pressure Glow Discharge Detector for Capillary Column Gas Chromatography

 The use of the change in the oscillation frequency of the current of a new atmospheric helium glow discharge for sensitive signal detection for gas chromatography is studied. The effluent of a capillary column is directed into the glow discharge cell perpendicular to the axis of the glow discharge that existed between a platinum anode and cathode. A stable discharge is obtained when several hundred volts are applied between the 0.2-mm gap between the anode and cathode. The effects of the electrode gap, discharge voltage and gas flow rate on the baseline frequency and discharge current were investigated. The chromatogram shows that the discharge current and discharge gap have a strong influence on the detector response. The discharge current shows positive peaks; however, frequency peaks are positive or negative depending on the discharge conditions. The response of the detector is in the femto-mole and pico-mole range for nonane and decane. Received August 5, 1997. Revision September 2, 1999     

Piezoelectric Crystal Liquid Flow Detection Systems Based on Alkyl (C18)‐Benzo‐15‐Crown 5 for Organic Compounds and Metal Ions

A water in soluble long‐chain crown ether alkyl (C18)‐benzo‐15‐crown‐5 was synthesized and applied as a coating material on quartz crystal membranes of a liquid flow piezo electric crystal sensor. The oscillating crown ether‐coated piezo electric (PZ) crystal with a home‐made computer inter face was prepared as a liquid chromato graphic (LC) detector for organic species and metal ions in aqueous solutions. The oscillating frequency of the quartz crystal decreased due to the adsorption of organic molecules or metal ions on crown ether molecules. Effects of functional group, molar mass, steric hindrance, and polarity of organic molecules on frequency responses of the crown ether coated PZ crystal detector were investigated. The frequency responses of the crown ether coated PZ crystal detector for various molecules were in the order: amines > carboxylic acids > alcohols > ketones. The crown ether PZ detector also exhibited good sensitivity for some heavy metal ions and the frequency shifts were in the order: Cr³⁺ » Pb²⁺ > Co²⁺ > Cd²⁺ > Ni²⁺ > Cu²⁺. The crown ether coated piezo electric crystal LC detector demonstrated low detection limits for various polar organic molecules, e.g., 6.0 × 10^?5 M for propylamine, and metal ions, e.g., 2.9 × 10^?5 M (1.8 ppm) for Cu²⁺; the crown ether PZ detector also gave good reproducibility when re used. A quite sensitive electrochemical quartz crystal microbalance (EQCM) detection system was also set‐up for detecting trace heavy metal ions in solutions. The variation in frequency of the PZ crystal and the diffusion current were observed simultaneously after the reduction in heavy metal ions such as Cu²⁺ and Ni²⁺. The EQCM detection system exhibited fairly good sensitivity, e.g., 112 Hz/ppm for Cu²⁺ and a good detection limit, e.g., 0.13 ppm for Cu²⁺ ions. Comparison between EQCM and PZ detection systems was made and discussed.     

Modified flame ionization detector for the analysis of large molecular weight polar compounds by capillary supercritical fluid chromatography

The modifications made to a flame ionization detector (FID) to facilitate the detection of large molecular weight polar compounds analyzed by capillary supercritical fluid chromatography are described. Some specific examples are given to demonstrate that polar compounds can be effectively eluted using deactivated fused silica capillary columns and supercritical carbon dioxide at 40°C.     

顶空固相微萃取-气相色谱表面发射火焰光度检测法测定底泥中的丁基锡化合物

固相微萃取可用于多种样品基体中挥发、半挥发性有机化合物的测定。将固相微萃取技术应用于底泥样品中丁基锡化合物的富集和萃取,以气相色谱分离结合表面发射火焰光度检测器检测,方法灵敏、快速,一丁、二丁、三丁基锡的检测限可达16.9、1.58和0.17ng/g。     

Determination of butyl- and phenyltin compounds in human urine by HS-SPME after derivatization with tetraethylborate and subsequent determination by capillary GC with microwave-induced plasma atomic emission and mass spectrometric detection

A headspace solid-phase micro-extraction (HS-SPME) method was developed and optimized for gas chromatographic separation and determination of commonly found organotin compounds in human urine after potential exposure. Butyl- and phenyltin compounds were in situ derivatized to ethylated derivatives by sodium tetraethylborate (NaBEt₄) directly in the urine matrix. The relevant parameters affecting the yield of the SPME procedure were examined using tetrabutyltin as internal standard. The method was optimized for direct use in the analysis of undiluted human urine samples and mono-, di- and tri-substituted butyl- and phenyltin compounds could be determined after a 15-min headspace extraction time at room temperature. The selectivity of the microwave-induced plasma atomic emission detector (MIP-AED) as an element specific detector in combination with the relatively selective sample preparation technique of HS-SPME allowed the interference-free detection of the organotin compounds in all cases. A quadrupole mass spectrometer was used in parallel experiments as a detector for the confirmation of the identity molecular structure of the eluted compounds. The performance characteristics of the developed method are given for the determination of mixtures of these compounds. Finally the proposed method was applied to the analysis of several human urine samples.