Supercritical fluid chromatography of petroleum products using flameless sulfur chemiluminescence detection

Supercritical fluid chromatography using flameless sulfur chemiluminescence detection has been investigated for the analysis of sulfur compounds in petroleum products. The chromatography and detection system was easy to implement and exhibited good precision, linearity, selectivity, and sensitivity. A minimum detectable limit of 0.3 pg sulfur/s was obtained, and response to sulfur in different sulfur species was nearly equimolar.     

Determination of Sulfur Compounds in Air by Chemiluminescence

Abstract

The present review is devoted to applications of chemiluminescence to the analysis of trace sulfur species in air. Determinations of oxidized (sulfur dioxide and sulfite), reduced (hydrogen sulfide, dimethyl sulfide, carbonyl sulfide, carbon disulfide and mercaptans) and/or sulfur compounds in general are described and some practical considerations are discussed. The development of detectors based on chemiluminescence in the aproximately last fifteen years is also reviewed.     

Simultaneous Measurement of Hydrocarbons and Sulfur Compounds using Flame Ionization and Sulfur Chemiluminescence Detection for Sulfur Simulated Distillation

A gas chromatographic system for the simultaneous acquisition of hydrocarbon and sulfur chromatograms was developed. Detection of sulfur compounds is achieved using a sulfur chemiluminescence detector (SCD) mounted in series with a flame ionization detector (FID). A constant fraction of the effluent of the FID is transferred to the SCD by means of a fixed restrictor. Unlike previous versions of this approach, the FID is not used to generate the chemiluminescent sulfur species. Rather, the FID is operated under optimum conditions for hydrocarbon analysis and a furnace is used to generate the chemiluminescent sulfur species. The system permits dual acquisition of the hydrocarbon and sulfur signals in a single analysis with a single column, since the detectors are operated in a serial fashion. The application of sulfur simulated distillation using this approach was examined, since this requires simultaneous universal and sulfur selective detection. Precision of absolute response of both the FID and SCD was typically less than 2% RSD for a standard reference material.     

Selective chemiluminescence detection of sulfur-containing compounds coupled with nitrogen—phosphorus detection for gas chromatography

A new sulfur and nitrogen—phosphorus detector for gas chromatography is described. The detector is an integrated thermionic ionization— chemiluminescence device permitting simultaneous detection of sulfur-containing and nitrogen- or phosphorus-containing compounds. This new flameless detector utilizes a heated rubidium-doped ceramic bead in a thermionic ionization chamber to produce sulfur monoxide from sulfur compounds. The SO is mixed with O₃ and the resulting chemiluminescence is monitored with a photomultiplier tube, providing sulfur-selective detection. The thermionic ionization detector signal serves as an independent second response channel, affording simultaneous selective and sensitive nitrogen—phosphorus detection. Two chromatograms are obtained, one in which selectivity is exhibited for nitrogen and phosphorus compounds, and the other for sulfur compounds present in the sample.     

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.     

原油中芳香硫化合物形态分布的研究

建立了原油中多环芳香硫化合物形态分布的研究方法。采用氯化钯/硅胶配位交换色谱分离原油中的芳香硫化合物,并用气相色谱/质谱分析、气相色谱-硫化学发光检测法结合色谱保留指数,鉴定出原油中的100多个多环芳香硫化物,包括含烷基取代基的苯并噻吩和二苯并噻吩类硫化物。定量分析表明,二苯并噻吩类化合物的含量占芳香硫化合物总量的91%左右。该方法可用于不同来源的原油中芳香硫化合物的形态分布研究。     

催化裂化汽油中硫化物类型分布的气相色谱-硫化学发光检测的方法研究

采用气相色谱-硫化学发光检测器(GC-SCD),建立了催化裂化汽油(FCC汽油)中各种硫化物类型分布的分析方法。考察了色谱条件对催化裂化汽油中各种硫化物分离的影响,定性了某催化裂化汽油中的58个硫化物。采用该方法,硫化物中的硫在其质量浓度为0.5~800.0 mg/L时,其峰面积与质量浓度呈较好的线性关系,相关系数达0.999,其响应与硫化物的类型无关。FCC汽油中几种主要硫化物(噻吩、正丁硫醇、2-甲基噻吩、3-甲基噻吩、2,4-二甲基噻吩)的浓度测定值的相对标准偏差(RSD)均小于5.0%。当信噪     

Sulfur and nitrogen chemiluminescence detection in gas chromatographic analysis

Sulfur and nitrogen compounds exist in a wide variety of analytical samples, from harmful contaminants in refinery streams to important ingredients in certain beverages, spices and condiments. Accurate determination of sulfur/nitrogen concentrations in these diverse samples is very important for process monitoring, quality control, product development, as well as basic research in these different industries. Due to the complex nature of the matrices, and the fact that the sulfur/nitrogen analytes usually exist at low concentrations, an element-selective detector for sulfur/nitrogen is indispensable to the GC analysis of these samples. To meet this challenge, sulfur and nitrogen chemiluminescence detectors for GC have become one of the most powerful tools available to analytical chemists, thanks to their high sensitivity, selectivity and equimolar detector response. In this brief review, an overview of the chemiluminescence detector operating principles, as well as the detector characteristics is presented. Examples of their applications in petroleum refinery, environmental analysis and food/flavor industry are presented. The two chemiluminescence detectors have also been combined into one convenient package and an example of applications of the simultaneous sulfur/nitrogen chemiluminescence detector is also provided.     

Advanced Methodologies for Adsorption/Thermal Desorption with Tenax-TA for the Analysis of Polycyclic Aromatic Hydrocarbons and Sulfur Compounds

We have evaluated an analytical method for the determination of polycyclic aromatic hydrocarbons (PAHs) and sulfur compounds in air by means of adsorption/temperature-programmed thermal desorption (ATPTD) with small bed volume (0.08g) Tenax-TA cartridges, followed by a cryogenic trap in a precolumn with liquid nitrogen as an appropriate concentration method before capillary gas chromatography is described. The enriched components from the adsorption cartridges are transferred to the capillary column with a valveless switching system. Recoveries were determined for the complete ATPTD method. Desorption recoveries near 100% were found for various of polycyclic aromatic hydrocarbons and sulfur compounds. The sulfur compounds known to cause nuisance odors in the atmosphere near sulfur recovery and sewerage treatment works were also determined.     

Sorptive Enrichment of Sulfur Compounds from Gaseous Samples on Polydimethylsiloxane

A method has been developed for preconcentrating the volatile sulfur compounds from gaseous samples using a trap filled with a sorption material, polydimethylsiloxane(PDMS), without the need for extensive cryotrapping with liquid cryogens. The system is based on enrichment of the solutes on a packed bed of 50% (w/w) PDMS on solid support without cryotrapping and is then analysed by using thermal desorption followed by capillary column (GS‐GASPRO) gas chromatography with simultaneous sulfur‐selective detection. The practicality of the system was demonstrated by the analysis of natural gas. Using the system described here, the sulfur gaseous compounds known to cause nuisance odors in the natural gas could be quantitatively trapped. The application of 50% PDMS on silcoport? for the analysis of sulfur compounds from gaseous samples has been proved to be useful.     

Air analysis using tenax collection with jet-separator enrichment and ion trap mass spectrometric analysis

A dual adsorbent trap inlet system has been developed for an ion trap mass spectrometer (ITMS) to provide a rapid and sensitive system for screening of volatile organic compounds in air. The system employs three stages of concentration: preconcentration on an adsorbent Tenax trap, focusing in a cryogenic collection trap, and jet separator enrichment immediately prior to analysis by ITMS. Ten minute integrated samples are collected and analyzed immediately. The detection limit is 0. 9 parts-per-trillion by volume (pptrv) based on toluene as the analyte, and the reproducibility is 2% or better. Ambient air was analyzed for toluene on April 4, 1996 in Los Alamos, New Mexico, and concentrations ranged from 11–158 pptrv.     

Sulfur speciation of Kuwaiti crude oils fractions using two-dimensional gas chromatography

The main objective of this study is to develop a methodology for sulfur compounds speciation using two-dimensional gas chromatography coupled with a flame ionization detector and sulfur chemiluminescence detectors. The methodology enhances the ability to detect and quantify the refractory sulfur in petroleum distillates, and it was utilized to screen the molecular differences between distillates of two Kuwaiti heavy crude oils from different reservoirs but with similar physical properties. Despite the similarity in the physical properties, the detailed comparative analysis indicated significant differences in molecular composition, which suggests substantial differences in crude oil processability based on the reactivity of the detected compounds. The distillates that have been considered in this study include heavy naphtha, kerosene, and gas oil. The compositional differences between the distillates were observed using the two-dimensional gas chromatography system with an in-house developed method. This method groups the sulfur compounds into thiols, benzothiophenes (BTs), and dibenzothiophene (DBTs), and it can handle any atmospheric distillate up 365 °C. Furthermore, the method includes the possibility of identifying and quantifying a total number of 44 sulfur species, which covers the previously mentioned sulfur groups.     

二氧化硫分析研究进展

亚硫酸盐广泛用作食品添加剂、酶抑制剂、漂白剂等。二氧化硫是工业过程中的中间产物,它是一种有害的空气污染物。本文概述了食品及环境中的亚硫酸盐及二氧化硫分析方法的最新进展。     

Comparison of combustion sources for sulfur chemiluminescence detection

Three different types of SCD combustion source have been evaluated for use in the chromatographic analysis of atmospheric sulfur compounds. The conventional FID source and the newer inverted burner source were found to be less sensitive and less stable than the flameless design. Overall, the flameless source was superior for use with HRGC-SCD.     

汽油馏分的硫化物形态分布研究

采用气相色谱和硫化学发光检测(GC-SCD)技术,经过对色谱条件的优化,建立了汽油馏分中硫化物形态分布的测定方法。用标准物质的保留时间辅以化学法脱除硫醇、硫醚的方法对107个硫化物进行了定性;标准硫化物保留时间重复测定结果的相对标准偏差(RSD)≤0.25%。用内标法对主要的硫化物和总硫含量进行了定量,方法的加标回收率为96%~115%;同一样品重复测定5次,含硫大于7 mg/kg的硫化物组分重复测定结果的RSD≤8.9%。所建立的方法可用于不同装置的汽油馏分的硫化物形态分布规律的研究。     

气相色谱法测定催化柴油中硫化物类型分布及数据对比

采用气相色谱-氢火焰离子化检测器-硫化学发光检测器（GC—FID—SCD）联用技术,建立了催化柴油中各种硫化物类型分布的分析方法。考察了色谱条件对催化柴油中各种硫化物分离的影响,定性了某催化柴油中的120多个硫化物,该方法还可以同时提供催化柴油中正构烷烃含量的分布信息。硫化物中的硫在1．5—700mg／L时其峰面积与质量浓度呈较好的线性关系,相关系数达0．9999,响应与硫化物的类型无关。催化柴油中苯并噻吩、4-甲基苯并噻吩、二苯并噻吩、4-甲基二苯并噻吩和4,6-二甲基二苯并噻吩等主要硫化物浓度测定的相对标准偏差（RSD）均小于5．0％。当信噪比（S／N）为3时,测得苯并噻吩硫的检出限为0．1mg／L。将该方法用于不同来源柴油中各种硫化物类型分布的研究,并与气相色谱一原子发射光谱检测器（GC—AED）测硫的数据进行了对比,两种检测器的定量结果大多数具有较好的相关性,相关系数大于0．95。     

焦化汽油中硫化物类型分布的气相色谱-硫化学发光检测方法

建立了焦化汽油中硫化物类型分布的气相色谱-硫化学发光检测分析方法。考察了色谱条件对焦化汽油中各种硫化物分离的影响,定性了某焦化汽油中的74个硫化物。以硫化氢、乙硫醇、正丙硫醇、噻吩、2-甲基噻吩、2-乙基噻吩、2-丙基噻吩、碳四噻吩(tR=40.28 min)、苯并噻吩、甲基苯并噻吩(tR=58.13 min)的保留时间为尺度,计算了焦化汽油中各种硫化物的保留指数,并可推广到其他类型的汽油馏分中各种硫化物保留指数的计算,为仅能提供硫化物信息的仪器提供了可靠的定性依据。焦化汽油中几种主要硫化物(异丙硫醇、正丙硫醇、正丁硫醇、2-甲基噻吩、3-甲基噻吩、2,4-二甲基噻吩、2,3,4-三甲基噻吩)含量测定值的相对标准偏差均小于5%。当信噪比为3时,测得硫的检测限为0.05 mg/L。研究发现:同其他类型的汽油相比,焦化汽油的硫含量较高且所含硫醇比例明显偏高,2-甲基噻吩和3-甲基噻吩的含量差别较大。该法可为加氢脱硫催化剂和工艺的研究提供数据。     

Evaluation of multi-walled carbon nanotubes as an adsorbent for trapping volatile organic compounds from environmental samples

A type of purified multi-walled carbon nanotubes (PMWCNTs) prepared by catalytic decomposition of methane, with a surface area of 98 m2/g, was evaluated as an adsorbent used for tapping volatile organic compounds (VOCs). The performance in evaluation was based on breakthrough volumes (BTVs) and recoveries of selected VOCs. PMWCNTs were also used as a trap packing material to adsorb VOCs purged from spiked water sample. Due to their porous structure, PMWCNTs were found to have much higher BTVs than that of Carbopack B, a graphitized carbon black with the same surface area as PMWCNTs. The recoveries of the tested VOCs trapped on PMWCNTs ranged from 80 to 110%, and not affected by the humidity of purge gas. The results indicate that PMWCNTs are a potential useful adsorbent for direct trapping VOCs from air samples and may be a supplement to VOCARB 3000, a commercially available trap, in purge-and-trap system to preconcentrate VOCs from water samples.     

Application of a unique selective PLOT capillary column for the analysis of oxygenated compounds in ambient air

Summary A new PLOT column (CP-LOWOX) designed specifically for the analysis of oxygenated compounds has been used for the gas chromatographic determination of semi-volatile carbonyl compounds. The separation behavior of the new column was investigated by comparing it with the widely used non-polar polydimethylsiloxane and polar poly(ethylene glycol) columns. The CP-LOWOX column has unique selectivity for aldehydes and ketones enabling a selective separation of these analytes from predominating hydrocarbon matrices. Application of the CP-LOWOX column for the analysis of polar compounds in ambient air is demonstrated. Sampling was performed by adsorptive enrichment coupled with thermal desorption. The suitability of Tenax TA and a multi-bed adsorbent trap Carbotrap C and Carbotrap) was tested for the sampling of semivolatile carbonyl compounds. Presented at Balaton Symposium on High Performance Separation Methods, Siófok, Hungary, September 1–3, 1999     

Detection of volatile organic compounds by temperature-programmed desorption combined with mass spectrometry and Fourier transform infrared spectroscopy

A temperature-programmed desorption (TPD) device connected to a mass spectrometer was used to detect volatile organic compounds from air samples. The main aim was to develop an analytical method, by which both non-polar and polar organic components can be detected in the same run. In TPD, the adsorbed compounds are desorbed from the resin more slowly than in the conventional trapping techniques, such as purge-and-trap technique, in which the resin is flash-heated and the compounds are desorbed at the same time to a cryogenic trap or an analytical column. In TPD, the adsorbent resin acts also as an analytical column. In this way it is possible to obtain more rapid analysis, and also a more simple instrumentation, which can be used on-line and on-site. In this work, a new version of TPD device, which uses a resistor for heating and a Peltier element for rapid cooling, was designed and constructed. Various adsorbent resins were tested for their adsorption and desorption properties of both polar and non-polar compounds. When using a mixture of adsorbent resins, Tenax TA and HayeSep D, it was possible to analyze both polar, low-molecular weight compounds, such as methanol and ethanol, and non-polar volatile organic compounds, such as benzene and toluene, in the same run within 15 min including sampling. The same TPD principle was also tested using a Fourier transform infrared spectrometer as an analytical instrument, and the results showed that it was possible to obtain a separation of similar compounds, such as hexane and heptane, and still retaining the same sensitivity as the original on-line FTIR instrument.