Flow injection gas chromatography with sulfur chemiluminescence detection for the analysis of total sulfur in complex hydrocarbon matrixes

A fast and reliable analytical technique for the determination of total sulfur levels in complex hydrocarbon matrices is introduced. The method employed flow injection technique using a gas chromatograph as a sample introduction device and a gas phase dual‐plasma sulfur chemiluminescence detector for sulfur quantification. Using the technique described, total sulfur measurement in challenging hydrocarbon matrices can be achieved in less than 10 s with sample‐to‐sample time <2 min. The high degree of selectivity and sensitivity toward sulfur compounds of the detector offers the ability to measure low sulfur levels with a detection limit in the range of 20 ppb w/w S. The equimolar response characteristic of the detector allows the quantitation of unknown sulfur compounds and simplifies the calibration process. Response is linear over a concentration range of five orders of magnitude, with a high degree of repeatability. The detector's lack of response to hydrocarbons enables direct analysis without the need for time‐consuming sample preparation and chromatographic separation processes. This flow injection‐based sulfur chemiluminescence detection technique is ideal for fast analysis or trace sulfur analysis.     

气相色谱法测定天然气中的硫化物

用气相色谱法,选择脉冲火焰光度检测器（PFPD）,在甲基硅油毛细管色谱柱上分析天然气中的硫化物。该方法灵敏度高,选择性好,结果准确,相对标准偏差小于1.1%。     

Quantitative determination of sulfur compounds in FCC gasolines by AED. A study of the effect of catalyst type and catalytic conditions on sulfur distribution

The identification and quantification of sulfur-containing compounds in gasoline has become an area of interest because of impending legislation regulating total sulfur levels in these fuels. To study the effects of catalyst type and catalytic conditions on gasoline sulfur distribution, a method has been developed employing both the compound-independent and element-specific response of the atomic emission detector (AED). Calibration and quantification can be accomplished even where standards are not available, owing to the nature of the AED response. Compounds were separated on a thick film polydimethylsiloxane column. An external calibration curve was applied to the area responses of individual sulfur components in the sulfur chromatogram, and the concentrations of each were calculated. Summation of these sulfur concentrations over the gasoline range yields the total sulfur content of the gasoline. The method is applicable to the determination of these compounds in raw crude oils, finished gasolines, fluid cracking catalyst (FCC) unit gasolines, and fluid catalytic cracking “model” compound studies. A prefractionating column was employed to remove heavy (>C₁₃) materials; prefractionation is not, however, necessary for distilled or commercial gasoline samples. Detection limits, linearity, detector stability, and accuracy are discussed.     

柴油馏分中含硫化合物组成与分布特征

采用毛细管气相色谱/脉冲火焰光度检测器(GC/PFPD,Gas Chromatograph/ Pulsed Flame Photometric Detector)对新疆独山子石化公司炼油厂的五种柴油馏分中的硫化物进行了分析。结果表明,常一线馏分中所含的硫化物主要是C0~4苯并噻吩;常二线馏分中除含有C_1~4苯并噻吩外还含有大量的C_0~3二苯并噻吩及部分未知硫化物;焦化柴油中硫化物组成最为复杂,包含中间馏分油中所有常见的硫化物类型;而催化裂化柴油和加氢柴油中硫化物类型主要为烷基苯并噻吩和烷基二苯并噻吩,其中加氢柴油中的硫化物相对丰度比催化裂化柴油低的多。     

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.     

Dual low thermal mass gas chromatography–mass spectrometry for fast dual-column separation of pesticides in complex sample

A method is described for fast dual-column separation of pesticides by use of dual low thermal mass gas chromatography–mass spectrometry (dual LTM-GC–MS) with different temperature programming. The method can provide two total ion chromatograms with different separation on DB-5 and DB-17 in a single run, which allows improved identification capability, even with short analysis time (<17 min). Also simultaneous detection with MS and elemental selective detector, e.g. pulsed flame photometric detection (PFPD) was evaluated for fast dual-column separation of 82 pesticide mixtures including 27 phosphorus pesticides. Dual LTM-GC–MS/PFPD was applied to analysis of pesticides in a brewed green tea sample with dual stir bar sorptive extraction method (dual SBSE).     

Identification of control parameters for the sulfur gas storability with bag sampling methods

Air samples containing sulfur compounds are often collected and stored in sample bags prior to analysis. The storage stability of six gaseous sulfur compounds (H₂S, CH₃SH, DMS, CS₂, DMDS and SO₂) was compared between two different bag materials (polyvinyl fluoride (PVF) and polyester aluminum (PEA)) at five initial concentrations (1, 10, 100, 1000, and 10,000 ppb). The response factors (RF) of these samples were determined after storage periods of 0, 1, and 3 days by gas chromatography–pulsed flame photometric detector (GC–PFPD) combined with an air server (AS)/thermal desorber (TD) system. Although concentration reduction occurred more rapidly from samples of the high concentration standards (1000 and 10,000 ppb), such trends were not evident in their low concentration counterparts (1, 10, and 100 ppb). As such, temporal changes in RF values and the associated loss rates of most sulfur gases were greatly affected by their initial concentration levels. Moreover, the storability of oxidized sulfur compound (SO₂) was greatly distinguished from that of reduced sulfur compounds (RSCs), as the former almost disappeared in the PVF bag even after one day. The results of our study confirm that storability of gaseous sulfur species is affected interactively by such variables as initial gas concentration level, bag material type, and oxidation status with the associated reactivity.     

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.     

Analysis of sulfur-containing compounds in crude oils by comprehensive two-dimensional gas chromatography with sulfur chemiluminescence detection

This paper reports an analytical method for separating, identifying, and quantifying sulfur-containing compounds in crude oil fraction (IBP-360 degrees C) samples based on comprehensive two-dimensional gas chromatography coupled with a sulfur chemiluminescence detector. Various sulfur-containing compounds and their groups were analyzed with one direct injection. 3620 peaks were detected including 1722 thiols/thioethers/ disulfides/1-ring thiophenes, 953 benzothiophenes, 704 dibenzothiophenes, and 241 benzonaphthothiophenes. The target sulfur compounds and their groups were identified based on the group separation feature and structured retention of comprehensive two-dimensional gas chromatography as well as standard substances. The quantitative analysis of major sulfur-containing compounds and total sulfur was based on the linear response of the sulfur chemiluminescence detector using the internal standard method. The sulfur contents of target sulfur compounds and their groups in 4 crude oil fractions were also determined. The recoveries for standard sulfur-containing compounds were in the range of 90-102%. The quantitative result of total sulfur in the Oman crude oil fraction sample was compared with those from ASTM D 4294 standard method (total S by X-ray fluorescence spectrometry), the relative deviation (RD%) was 4.2% and the precision of the method satisfactory.     

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。     

The Quantitation of Heroin and Selected Basic Impurities via Reversed Phase HPLC. II. The Analysis of Adulterated Samples

Abstract

Methodology is presented for the quantitation of heroin, O⁶-monoacetylmorphine, acetylcodeine, noscapine and papaverine in adulterated illicit heroin samples. Reversed phase chromatography was employed using an HS-5 C18 column with a gradient system. This methodology used a multimode detection scheme which consisted of a photodiode array detector in series with a dual electrochemical detector in the parallel mode. Owing to its high specificity for O⁶-monoacetylmorphine, electrochemical detection via the oxidation mode proved necessary for the quantitation of this compound in samples highly adulterated with quinine. The use of relative retention times, UV spectra and dual electrochemical response ratios for the screening of adulterants in heroin is discussed.     

GC: a review of the state-of-the-art column technologies for the determination of ppm to ppb levels of oxygenated, sulfur, and hydrocarbon impurities in C1-C5 hydrocarbon streams

The determination of ppm to ppb levels of sulfur, oxygen-containing, and certain reactive hydrocarbons in bulk hydrocarbon feedstocks is important in the petroleum and petrochemical industry to minimize catalytic deactivation and improve product quality. Gas chromatography, coupled with selective or ultratrace universal detection (or both), is ideal in most cases for such analysis. However, to enhance selectivity and quantitation at the trace levels, optimized stationary phases are required. These phases are usually of the adsorbent type. This paper summarizes the performance of several state-of-the-art phases for the analyses of trace key hydrocarbons, sulfur, and oxygenated components.     

Improved determination of sulpiride in plasma by ion-pair liquid chromatography with fluorescence detection

A specific and sensitive high-performance liquid chromatographic method for the measurement of sulpiride in plasma is described. The internal standard used was veralipride, a structurally related substituted benzamide. A fluorescence detector with maximum excitation at 300 nm and maximum emission at 365 nm was used for quantitation. After an alkaline extraction procedure, the benzamides were separated on a 5-micron ODS column using a large organic counter ion in the mobile phase. The detector response was linear from 10 to 1000 ng/ml and the detection limit was 10 ng/ml, which is sensitive enough for pharmacokinetic studies. The suitability of the method for the analysis of biological samples was tested by studying the variation with time of plasma concentrations of sulpiride in normal human volunteers after a single therapeutic 200-mg oral dose of three different formulations of sulpiride.     

加拿大合成原油减压馏分油及其催化裂化液体产物中含硫化合物分析

应用GC PFPD和GC MS技术对加拿大油砂合成原油（Synthetic Crude Oil,简称SCO）减压馏分油（350 ℃~500 ℃）中的含硫化合物进行定性定量分析。结果表明,所含硫化物主要是C3~7二苯并噻吩,而催化裂化反应后则以短侧链二苯并噻吩为主,还含少量烷基苯并噻吩和烷基噻吩,三者的质量分数分别为82.04%、13.42%和0.56%,均属于难以加氢脱除的含硫化合物。SCO减压馏分油和大港减压馏分油按不同比例混合后进行催化裂化反应,随着加拿大合成原油减压馏分油搀兑比增加,所得液相产物中烷基噻吩和烷基苯并噻吩质量分数逐渐降低,烷基二苯并噻吩相对质量分数增加,4-MDBT是丰度最高的含硫化合物,显示加氢油的特征。随掺兑比的提高,液相产物中总硫质量分数和柴油馏分中硫质量分数逐渐增高,而汽油馏分中硫质量分数逐渐降低。     

The characterization and quantitation of sulfur-containing compounds in (heavy) middle distillates by LC-GC-FID-SCD

A modified sulfur chemiluniinescence detector (SCO) has been interfaced to a HPLC-HRGC hyphenated system. This combination enables the full characterization and quantitation of the sulfur containing compounds in (heavy) middle distillate oil fractions (boiling range 150–450°C). The system is suited to identify and determine the various groups of orgaiio-sulfur structures such as: thiols + sulfides + thiophencs, benzothiophenes, dibenzothiophenes and benzo-naphthothiophenes. Within these groups a separation according to boiling point is accomplished. Therefore it allows the separation, identification and quantitation of a number of individual species, especially those which are refractory to hydrodesulfu-rization (HDS), such as 3-methyl-benzothiophene, 4-methyl-dibenzothiophene and -J,6-dimethyl-dibenzothiophene. The analysis of these groups and specific compounds is the key in understanding the kinetics of the chemistry involved in HDS. The complete instrumental set-up is fully automated by computer control. To suppress possible interferences and quenching of the sulfur response of the SCL from (large amounts of) hydrocarbons, it is aligned above the adapted flame ionization detector (FID) of the GC. This renders a sensitivity of the SCO for sulfur of 2 pg. s^?1, which corresponds to a minimum detectable level for individual sulfur species in oil fractions for the complete system of 1 ppm (mg. kg^?1) sulfur. Its linear dynamic range exceeds 10⁵, which means that also untreated, high sulfur containing feedstocks can be analyzed directly. The selectivity of sulfur to carbon of the modified SCO exceeds 10⁶. A number of HDS feedstocks and desulfurized products of different desulfurization levels have been analyzed with the system. From the analysis results the behavior of the refractory compounds in HDS can now be followed closely.     

Determination of organotins in aquatic food by gas chromatography with pulsed flame photometric detection

A method based on gas chromatography (GC)-pulsed flame photometric detection (PFPD) was developed to determine the levels of organotins in aquatic food. After being purified by gel-permeation chromatography in ethyl actate-tetrahydrofuran, the organotin compounds were derivatized by pentylmagnesium bromide. The derivative products were injected into the GC system and detected by PFPD (sulfur mode). The method was validated by analysis of the certified reference material and spiked samples. Recoveries of organotins ranged from 84.1 to 116.6% with relative standard deviation between 1.3 and 16.0% when spiked at levels of 2, 10, and 40 microg/kg. The limits of detection varied from 0.1 to 1.2 microg/kg for shellfish and 0.1 to 0.5 microg/kg for fish. The proposed method was suitable for determining organotins in aquatic foods.     

Solid-phase microextraction method for gas chromatography with mass spectrometric and pulsed flame photometric detection: studies of organoarsenical speciation

The development, optimization, and application of a novel method for arsenic speciation based on capillary gas-liquid chromatography with simultaneous quadrupole ion-trap mass spectrometric (MS) detection and pulsed flame photometric detection (PFPD) is described. The method couples the sensitive arsenic-selectivity of PFPD with the structure elucidation capability of molecular MS detection for the determination of trace levels of unknown organoarsenicals in complex matrices. The conditions that affect the PFPD response in the presence of interfering species were optimized using the sequential Simplex algorithm for three key factors: gate delay (18.3 ms), gate width (9.1 ms), and combustion gas composition (16.6 ml/min H2). Complete discrimination in the PFPD of the arsenic signal from interfering S-, C-, and OH-emitting species that are problematic in existing methods was achieved. Additionally, a revised interpretation of our previously reported mechanism [J. Chromatogr. A 807 (1998) 253] for the dithiol derivatization and subsequent GC-MS determination of dimethylarsinic acid is presented.     

Organotin speciation in environmental samples by capillary gas chromatography and pulsed flame photometric detection (PFPD)

Pulsed flame photometric detection (PFPD) for gas chromatography was applied to organotin compounds as standards and in environmental samples. Ethylated organotin species (n-propyl-, n-butyl- and phenyl-) were extracted from spiked artificial seawater and from an environmental sample. Selectivity towards tin is shown in the analysis of highly polluted seawater samples from a commercial port where no significant interferences are found. The self-cleaning capability and long-term stability of PFPD is shown in this work during 140 days of continuous operation. The absolute limit of detection for this capillary GC–PFPD technique ranged from 0.2 to 0.4 pg (Sn) for tetraethyl- to tetraphenyl-tin, allowing determination of sub-nanogram/litre concentrations of organotin compounds. © 1997 John Wiley & Sons, Ltd.     

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。     

A method to test the detectability of GC/PFPD for an extended concentration range with respect to reduced sulfur compounds

In this study, a possible means to extensively expand the quantifiable range of reduced sulfur compounds (RSC) in air has been investigated by a combined application of GC with pulsed flame photometric detector (PFPD) and a multifunction thermal desorber (TD) system. To comply with the purpose of this study, gaseous RSC standards containing the equimolar concentrations of H(2)S, CH(3)SH, DMS, DMDS, and CS(2 )were prepared at 11 concentration levels (i. e., 10 ppb-10 ppm (over 10(3 )range)). These standards were then used to derive three-point calibrations based on the modified injection through a TD (MITD). If the mean calibration slopes of each concentration level are normalized to that of CH(3)SH, the relative ordering is found as 0.65 (H(2)S): 1 (CH(3)SH): 1.34 (DMS): 2.24 (DMDS). The reproducibility of MITD method, when assessed in terms of relative standard error (RSE) for all calibration slopes, had the most stable pattern for DMDS (5.77%) and the least stable one for H(2)S (12.8%). The sensitivity of the MITD-based calibration generally improved with an increase in concentration levels of standard gas. Based on our study, the MITD technique is useful to extend quantification of GC/PFPD by allowing RSC detection over a 10(3) range.