Study of the surface ionization detector for gas chromatography

The structure of the surface ionization detector (SID) and the operation parameters of GC-SID were investigated to reduce peak tailing and to enhance sensitivity. The performances of the GC-SID, including its repeatability, linearity, sensitivity, selectivity, and tolerance towards water vapor, were evaluated systematically. Compared with nitrogen-phosphorus detector (NPD), the SID was able to detect fg level triethylamine, and selectively respond to alkylamines, some anilines, and some nitrogen heterocyclic compounds. Among alkylamines, the SID sensitivity to diisobutylamine was rather small. Even so, it was also still 10 times higher than that on NPD. The SID selectivity, defined as the sensitivity ratio between triethylamine and various tested non-nitrogen compounds, was higher than 10(6). It was found that the SID is highly tolerant towards water vapor, allowing direct injection of water sample. Finally, the GC-SID was applied to directly measure trace amines in headspace gases of rotted meat and trace simazine in tap water. The SID sensitivity to simazine was proven to be 5 times higher than that on flame ionization detector (FID). This study suggests that the SID is a promising GC detector.     

A new approach to the simultaneous multi-detection technique with electron capture and flame ionization in series

In order to avoid splitting at the column outlet for simultaneous multidetection, a new line of detector heads with the ionization cells coupled in series has been developed. The electron capture plus flame ionization detector (EC+FI-D) has been evaluated from the point of view of the sensitivity, the linear dynamic range and separation efficiency in a capillary column GC system. The performances of each section are the same as when a single ionization detector head is used.     

Flow‐modulated targeted signal enhancement for volatile organic compounds

Comprehensive two‐dimensional gas chromatography is a technique that is becoming more widespread within the analytical community, especially in the separation of complex mixtures. Modulation in comprehensive two‐dimensional gas chromatography can be achieved by manipulating temperature or flow and offers many advantages such as increased separation power, but one underutilized advantage is increased detectability due to the reduction of peak width from the use of a modulator. A flow modulator was used to selectively target analytes for increased detectability with a standard flame ionization detector operated at 100 Hz, without the need for cryogens or advanced modulation software. By the collection of the entire peak volume followed by peak transfer rather than further separation, an increase of 12 times in peak height and detectability was realized for the analytes tested using an internal loop modulator configuration. An external loop flow modulator configuration allowed for more volatile analytes (with k < 5), and demonstrated an analyte detectability enhancement factor of at least 6. The collection loop size can be readily increased with an external loop configuration to accommodate for these naturally broader peaks. This novel flow modulated targeted signal enhancement approach was applied to industrially significant analyses like the analysis of methanol in a hydrocarbon streams. Methanol was detected at 7 ppb with a conventional flame ionization detector and without the need for pre‐concentration.     

无衍生化-气相色谱法测定药用胶塞提取液中硬脂酸和棕榈酸

建立了无衍生化-气相色谱法测定药用胶塞提取液中硬脂酸和棕榈酸的分析方法. 采用3种不同介质（pH值为3的酸性缓冲溶液、pH值为10的碱性缓冲溶液、20%乙醇溶液）对胶塞进行提取,得到的提取液经正己烷萃取后,采用DB-FFAP（30 m×0.25 mm×0.25 μm）色谱柱进行分离,经火焰离子化检测器（FID）检测,外标法定量. 结果表明,在最优条件下,硬脂酸和棕榈酸峰形对称,分离效果和标准曲线线性良好,平均加标回收率为97.6%~100.5%,相对标准偏差（RSD）为0.4%~2.3%（n=6）,检出限（LOD）为1.0~1.5 mg/L. 方法前处理简单、准确度高,可用于药用胶塞提取液中硬脂酸和棕榈酸的检测.     

One-step separation of terpenoids from leaves extracts of Solanum cernuum by high-performance countercurrent chromatography

Solanum cernuum is a native shrub from Brazil that has been used as medicine since the nineteenth century. Although it has been utilized for a long time, there are few studies regarding its chemical composition and it motivated us to investigate this species. The dried leaves of S. cernuum were extracted with methanol and the obtained extract was further partitioned with different organic solvents. As part of our investigation, the n-hexane fraction was submitted to CCC with a nonaqueous solvent system composed of hexane, acetonitrile, and ethyl acetate (5:5:1, v/v/v). Three terpenoids were obtained by one-step separation and identified as 24-oxo-31-norcycloartanone (22.8 mg), lupeol (9.4 mg), and cycloeucalenone (13.4 mg). Complementarily, the solvents system used on the separation have had their compositions determined by gas chromotography–flame ionization detector (GC-FID).     

Analysis of sludge extracts by high resolution GC with selective detectors

Combination of various GC detectors by using a Varian effluent splitter with glass capillary columns has been found to be a rapid procedure for profiling organics extracted from sludges and river sediments. The selectivity and the increased sensitivity of the thermionic nitrogen-phosphorus detector (TSD), the electron capture detector (ECD), and the flame photometric detector (FPD) over the flame ionization detectors (FID) or mass spectrometers allow the detection of compounds present at trace levels without need for extensive sample cleanup. Furthermore, the combination of two selective detectors may supplement the information with regard to the chemical functionalities required for structure elucidation.     

Organic fuelled flames in selective ionization detectors for chromatography

Summary The selectivities of two flame-based ionization detectors identified as a Remote FID (RFID) and a Flame Thermionic Ionization Detector (FTID) have been improved by introducing methane as a fuel for the flame. Both the RFID and FTID feature a detector struture in which the ionization polarizer and collector are located several centimeters downstream of an oxygen-rich flame, rather than immediately adjacent to the flame as in a flame ionization detector. The RFID detects long-lived negative ions produced in the flame by the combustion of lead, tin, phosphorus, or silicon compounds. The FTID re-ionizes and detects neutral electronegative products generated by combustion of nitrogen, halogen, or phosphorus compounds. An organic-fuelled RFID can detect 1 pg Pb (Sn, P)/sec with a selectivity of the order of 10⁶ versus hydrocarbons. An organic fuelled FTID is applicable to detection of compounds at nanogram and higher levels. FTID selectivity for PCB compounds in a transformer oil matrix is of the order of 10⁵1. The improved selectivity achieved by using an organic-fuelled flame is also applicable to the detection of phospholipid and other non-volatile N, P, or Cl compounds using an FID/FTID detector accessory for a TLC/FID analyser.     

Surface ionization detector with a supersonic free jet for gas chromatography some applications

A new design for a gas chromatographic surface ionization detector based upon hyperthermal positive surface ionization has been developed: There were two requirements: supersonic free jet nozzle and the high work function surface of Re-oxide. This detector, which is highly sensitive in response to all organic compounds, can be operated as an universal detector with an additional selectivity towards some species that have low ionization energy, but with selectivity to a much lesser degree than a conventional surface ionization detector. The minimum detectable amount of toluene is ca. 10⁻¹² g/s with a linearity greater than 10⁴. Some applications are demonstrated using three examples for the analysis of different formulations: (1), terpene mixture, (2), polycyclic aromatic hydrocarbon mixture and (3), alkyl alcohol mixture.     

Gas-chromatographic determination of traces of <Emphasis Type="Italic">O</Emphasis>-isopropyl methylphosphonofluoridate (sarin) in soils using its diastereomers

A procedure was developed for determining traces of O-isopropyl methylphosphonofluoridate (sarin) in soils at a level of 2 × 10⁻⁴ mg/kg. The procedure is based on solvent extraction with a hexane-benzene mixture, the preconcentration of the extract to a small volume, the synthesis of dialkyl esters using secondary alcohol aluminates, and gas-chromatographic separation on an HP-1 column with a flame ionization detector. The determination error does not exceed 29%; the time of analysis is 1 h.     

Gas Chromatographic Determination of Caffeine in Beverages by Alkali Aerosol Flame Ionization Detection

The quantitative ability of the presented alkali flame ionization detector to determine the amount of caffeine in selected beverages is examined. A sample cleanup and concentration procedure is employed followed by gas chromatographic separation with alkali flame ionization detection. The amount of caffeine in 12-ounce containers of the beverages ranged from 35 mg to 60 mg. The linear response range of caffeine was observed to be 3.7 orders of magnitude.     

Determination of Isobutanol in Phosphoric Acid by Gas Chromatography

Isobutanol in phosphoric acid was detected by gas chromatography with a flame ionization detector. Samples with high content (>100 μg/ml) of isobutanol were diluted with a n-pentanol aqueous solution and the diluted solutions were directly injected into the GC column for the determination of isobutanol. For lower content samples, isobutanol was preconcentrated by vacuum distillation or CCl₄ extraction followed by activated alumina adsorption. In whole GC measurements, n-pentanol was used as an internal standard. The flame ionization detector is capable of detecting quantities of isobutanol as small as 5×10^?8g. With preconcentration, isobutanol at the concentration of 0.4 μg/ml or lower can be determined.     

Structure-type separation of diesel fuels by solid phase extraction and identification of the two- and three-ring aromatics by capillary GC-mass spectrometry

A simple and effective solid phase extraction (SPE) method using silica gel micro glass columns has been developed for the separation of diesel fuel into groups of aliphatic, and mono-, di- and polyaromatic hydrocarbons. It is based on a stepwise gradient of dichloromethane in n-pentane. The resulting fractions were analyzed by capillary gas chromatography with a flame ionization detector and coupled gas chromatography-mass spectrometry. Commercially available standards, and retention indices and mass spectra were used for identification of individual aromatic compounds. The principal polycyclic aromatic hydrocarbons (PAHs) in diesel fuel are naphthalene, biphenyl, fluorene, phen-anthrene and their alkylated derivatives. Sulfur-containing PAHs are mainly represented by methyl-substituted dibenzo-thiophenes.     

棒状薄层色谱/氢火焰法分析磺化酞菁钴的组成

研究建立了一种采用棒状薄层色谱／氢火焰离子检测（TLC／FID）对磺化酞菁钴组成进行定性、定量分析的方法。用薄层色谱并结合质谱分析 表明工业磺化酞菁钴中含有一磺化酞菁钴的两种同分异构体,二磺化酞菁钴的5种同分异构体及三磺化酞菁钴;用棒状薄层色谱／氢离子火焰检测方法可以对磺化酞菁钴中各组分进行定量分析。该方法操作简便,测定时间短,灵敏度高,可用于磺化酞菁钴工业合成的产品质量控制。     

Dynamic control of split flow in packed column supercritical fluid chromatography using dual resistively heated restrictors

Remote control of the vent/detector split flow ratio in packed column supercritical fluid chromatography (pSFC) with flame ionization detector (FID) is demonstrated using a dual heated restrictor method. Restrictors stemming from a Tee at the separation column outlet were, respectively, fixed into an FID and a vent port, and their individual temperatures were controlled using resistively heated wires. Subsequently, both system pressure and split flow could be manipulated. For example, for applied restrictor temperatures examined up to 600°C, corresponding vent/FID split flow ratios between 2 and 7 were observed depending on the port heated. As well, column pressures around 16–23 MPa were also achievable over the same range. Conversely, isobaric altering of the split flow ratio was possible when opposing positive and negative temperature gradients were applied at the two restrictors. Under these conditions, the system pressure varied less than 1% RSD over a 10 min period. As an application, the method was used to establish stable detector operation in the analysis of n‐alkanes under pSFC‐FID conditions that initiated flame instability. Results indicate that this technique could be a relatively simple and inexpensive means of controlling system pressure and detector split flow ratios in pSFC‐FID.     

Characteristics and performance of gas chromatographic detectors with glass capillary columns

A comparison of the characteristics and Performance of the flame ionization, electron capture, and flame photometric detectors with capillary columns is described. Factors which may affect the limits of detection, linearity, chromatographic peak shape, and other detector performance characteristics are discussed and compared with the results of a model derived for the behavior of concentration and mass flow-rate dependent chromatographic detectors used with capillary GC systems. Examples are given of highly complex and labile mixtures such as pesticide residues and products from coal hydrogenation.     

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.     

Open-tubular supercritical fluid chromatography with simultaneous flame ionization and chemiluminescent nitrogen detection

The use of a simultaneous detection system for open-tubular supercritical fluid chromatogrphic separation of aniline isomers, alkyl(C₈ to C₁₈)dimethylamines, a dialkylmethylamine mixture, and an extract of a Japanese horseradish power “Wasabi” is demonstrated. A chemiluminescent nitrogen detector (CLND) and a flame ionization detector (FID) were configured at the end of the open tubular column via a zero- to dead-volume tee. The dual detection was achieved with a post-column split at a 1:2.5 ratio for the CLND and FID, respectively. The optimized CLND showed virtually no response to non-nitrogenous components such as benzene, toluene, and methanol which were used as injection solvents in these applications.     

Separation of aromatic solvents from oil refinery reformates by a newly designed ionic liquid using gas chromatography with flame ionization detection

The aim of this study was to determine whether the new ionic liquid, N,N‐dimethyl‐2‐oxopyrrolidonium iodide, synthesized in our laboratory is a suitable solvent for the separation of aromatic components benzene, toluene, ethylbenzene, and xylenes from petroleum mixtures (reformates) in liquid–liquid extraction. In pursuance of the above aim, a method to extract all components of a mixture, containing four aromatic components simultaneously, was developed. A new ionic liquid and a previously used liquid were compared for their extraction abilities. These ionic liquids were, respectively, N,N‐dimethyl‐2‐oxopyrrolidinium iodide and 1‐ethyl‐3‐methyl imidazolium ethyl sulfate. The concentrations of each benzene, toluene, ethylbenzene, and xylenes component in the extract and raffinate phases were measured by gas chromatography with flame ionization detection as volume percent to determine the extraction ability of the ionic liquids. The results obtained for both the reformate samples and model mixtures indicated that the new ionic liquid was effective as an extracting solvent for the recovery of aromatic components from reformates. Also the analysis results, using gas chromatography with flame ionization detection, for the reformate samples were as good as the results obtained by a local oil refinery. The extraction results also show that the developed method is very suitable for the separation and analysis of aromatic components in reformates.     

Direct coupling of capillary supercritical fluid chromatography with double-focusing high resolution mass spectrometry

An integral restrictor interface with jet separator for coupling capillary column supercritical fluid extraction – supercritical fluid chromatography with high resolution mass spectrometry (SFE-SFC-MS) has been built and used for the analysis of a fatty acid ester, and of polymer additives with a wide range of masses. The mobile phase used was supercritical carbon dioxide; a flame ionization detector (FID) was used in parallel with the mass spectrometer. Different SFC-MS interface operating conditions, e.g. temperature, restrictor position, flow rate, and sample transfer conditions were optimized to obtain good sensitivity and separation for these applications. In addition, the sensitivity of measurements performed with the direct insertion probe and by SFC-MS interface have been compared.     

液液萃取–气相色谱法测定地表水中硝基苯

采用液液萃取–气相色谱法测定地表水中硝基苯的含量。采用盐酸调节水样至pH值为4左右,在200mL水样中加入8 g氯化钠,以甲苯为萃取剂,以CD–5MS色谱柱进行分离,氢火焰离子化检测器检测地表水中硝基苯的含量。硝基苯的质量浓度在10~150μg/L范围内与色谱峰面积呈良好的线性关系,线性相关系数r=0.999 4,方法检出限为0.24μg/L。加标回收率在91.6%~96.7%之间,测定结果的相对标准偏差小于3(n=7)。该方法操作简便,灵敏度高,适用于地表水中硝基苯的分析。