Ionization-based detectors for gas chromatography

At present, the application fields of high-purity gases (purity reached 99.999% and above) include the semiconductor manufacturing industry, chemical analysis, fuel cells, aerospace, medicine, etc., and the quality and purity requirements of high-purity gases are also getting higher and higher. As the only detector that can detect ppb-level trace impurities, the pulsed discharge helium ionization detector (PDHID) is the most used detector in the field of high-purity gases. The minimum detection limit of existing PDHID-related analysis methods is usually calculated theoretically. In order to verify the actual minimum detection limit of PDHID, a multi-group gas distribution system was used in this paper to dilute the permanent gas components in the high-purity gas, and the gas chromatograph with pulsed discharge helium ionization detector (GC-PDHID) was used to detect the obtained different concentrations of standard gases. The experimental results showed that PDHID possessed high sensitivity, good linearity, and a wide linear range. The actual minimum detection limit for the permanent gas components in the high-purity gas could reach the ng/g (ppb) level, which could realize the detection of ultra-low concentration samples, and further verify the actual minimum detection limit of PDHID. This experiment provides a reference basis for the analysis of trace gases in the gas industry, especially in industries such as high-purity and ultra-high-purity gases and gas for the electronics industry, and is of great significance in actual production work.

Chemiluminescent photon yields measured in the flame photometric detector on chromatographic peaks containing sulfur, phosphorus, manganese, ruthenium, iron or selenium

Evaluation of compound-independent calibration using gas chromatography with atomic emission detection

Determination of methyl tert.-butyl ether and tert.-butyl alcohol in seawater samples using purge-and-trap enrichment coupled to gas chromatography with atomic emission and mass spectrometric detection

Analysis of total petroleum hydrocarbons (TPHs) from impacted media involves the collection and preservation of samples followed by extraction, concentration, and clean-up of the sample extract as well as detection and quantification of the petroleum hydrocarbons (PHs). Extraction involves the use of methods such as continuous liquid-liquid extraction, purge and trap extraction, headspace analysis, separatory funnel extraction, solid-phase extraction, accelerated solvent extraction, mechanical shaking, microextraction, Soxhlet extraction, ultrasonic extraction, or supercritical fluid extraction, while the concentration of the extract is executed using the trapping method, Snyder column, Kuderna-Danish concentrator, or nitrogen evaporator. Extract clean-up before analysis is done directly using solid-phase cartridges or indirectly using alumina clean-up, silica gel clean-up, gel permeation clean-up, acid-base partition, and desulfurization technique. The measurement of TPHs in impacted media is most frequently done using gas chromatography (GC) coupled with a flame ionization detector, photoionization detector, or mass spectrometric detection. Other methods of final TPHs determination include infrared spectroscopy, gravimetry, ultraviolet fluorescence spectroscopy, immunoassay, and high-performance liquid chromatography. More importantly, the profile of unresolved complex hydrocarbon mixtures in a TPH-polluted sample is amply characterized and resolved using two-dimensional GC. Of all the analytical methods, ultraviolet fluorescence spectroscopy, gravimetry, and GC are more frequently used to determine TPHs levels in the environment.

Gas chromatographic detection modes for the plasma chromatograph

Sugarcane spirits are defined as beverages with an alcohol content ranging from 38 to 54 % v/v at 20 °C, obtained from the simple alcoholic distillation of sugarcane or fermented sugarcane must. Fruit spirits may be obtained directly from fruit or from fruit must that may or may not contain seeds by distillation, and present specific organo- leptic characteristics and an alcohol content of 36 to 54 % v/ v at 20 °C. The physicochemical and sensory qualities of these beverages are dependent on the nature and quality of the raw materials, fermentation, distillation and aging, and are organoleptically characterised by the presence of volatile organic compounds (VOC) (organic acids, aldehydes, esters, higher alcohols, terpenes, lactones and others). This paper presents studies performed to evaluate VOC in spirits. Among the volumetric and instrumental methods described to evaluate VOC in spirits, chromatographic methods are the most cited. Chromatographic techniques employed include high performance liquid chromatography, gas chromatogra- phy with flame ionisation detection, gas chromatography with mass spectrometric detection and two-dimensional gas chromatography with time-of-flight mass spectrometry.

Determination of epichlorohydrin in water and sewage samples

Research was conducted to determine if there is a correlation between the data gathered by field analytical instruments in analyzing soil contaminated with diesel fuel. One instrument was equipped with a flame ionization detector (FID) and the other a photoionization detector (PID). The results showed that the concentration readings of the PID and FID displayed a linear relationship for soil recently contaminated with diesel fuel. However, for soil containing weathered diesel fuel in the field, a logarithmic relationship between the PID and FID readings was displayed. It was also determined by laboratory experimentation that the PID and FID readings both exhibited log-linear decreases over time for uncovered diesel fuel-contaminated soil. It was concluded that the PID and FID can both individually be used to evaluate soil contaminated by diesel fuel and might be interchangeable depending on the needs of the researcher.

A simple gas chromatographic method has been developed for the simultaneous and sensitive analysis of inorganic (H2, CO, and CO2) and organic gaseous compounds (CH4, C2H4, C2H6, C3H6, C3H8, iso-C4H10, and n-C4H10). The analysis of these gases generally requires multi-columns and/or multi-detectors, whereas the proposed method uses a single micropacked column and a single pulsed discharge helium ionization detector (PDHID). All of the investigated peaks (except for the N2 and O2 peaks, which are the major components of air) show good separation when using an oven temperature program from 40°C to 300°C. This gas chromatography‐PDHID system yielded good linearity and a relative standard deviation of less than 5%. This sensitive and convenient method shows great potential in analyses of various types of gaseous compounds.

With a three-cylinder spark-ignition (SI) engine, formaldehyde (HCHO) and methanol (CH3OH) emission characteristics as well as the three-way catalytic converter (TWC) conversion efficiency were investigated when it ran on gasoline, M10, M20, and M85 (gasoline blended with 10, 20, and 85% of methanol in volume), respectively. HCHO and CH3OH were detected by gas chromatography (GC) with a pulsed discharge helium ionization detector (PDHID). Experimental results show that HCHO emission increases with engine speed, while CH3OH emission from a methanol/gasoline blend-fueled engine decreases with it. HCHO emission from a gasoline-fueled engine varies in a “U” curve with the engine torque. The addition of 10% methanol in gasoline doubles the HCHO emission. The increasing methanol fraction greatly improves HCHO and CH3OH emission; their concentrations are both approximately linear to the amount of cyclically supplied fuel methanol. CH3OH can be totally removed by lightened-off TWC. However, the HCHO concentration may increase rather than decrease via the conversion of TWC at high engine speeds.

Destruction of halogenated methanes by non-electron capture processes within an electron capture detector

Introduction . Seeds of Nigella sativa L. are widely known as a source of fatty oil with a very rare component-thymoquinone. The therapeutic potential of biologically active compounds of plant seeds covers a positive effect on the gastrointestinal tract, cardiovascular and immune systems. In addition, hypoglycemic, antioxidant, antitumor, oncoprotective, immunomodulating effects were found in thymoquinone. In addition to fatty oil and thymoquinone, a number of other significant compounds are present in the seeds, which also make up their own pharmacological asset. Aim. Study was to develop a processing flow chart and analyze the lipophilic and hydrophilic components of the seeds of N. sativa L. Materials and methods . The following methods were used as analytical methods: gas-liquid chromatography with a flame ionization detector - for the analysis of sterols and triterpenes; chromatography-mass spectrometry (gas-liquid chromatography with mass spectrometric detection) - for the study of essential oil; chromatography-mass spectrometry (high performance liquid chromatography with mass spectrometric detection) - to study flavonoids. To obtain individual fractions of biologically active compounds of seeds of N. sativa L., fractional extraction was used. Results and discussion . The principle of this approach in this case is to extract the entire lipid complex of seeds with n-hexane, followed by removal of the extractant. The thickened hexane extract is treated with ethyl alcohol, which extracts unsaponifiable compounds - terpenes, quinones, sterols and does not dissolve triacylglycerides. The seed meal remaining after hexane extraction is treated with ethyl alcohol 70 %, into which hydrophilic molecules, in particular flavonoids, pass. Conclusion . After transesterification, 5 compounds were identified in the lipophilic fraction of saponifiable lipids, the linoleic and oleic acids being dominant. A characteristic feature of this fraction is the presence of cis-11,14-eicosadiene acid, which can act as a marker element of the fatty oil of the seeds of N. sativa L. Sterols and triterpenes were found in the unsaponifiable fraction. The major component of this fraction is β -sitosterol. In addition to the indicated sterol, campesterol and stigmasteri are present. Triterpenes are represented by cycloartenol and its derivatives. Simple phenols, quinones and monoterpenes were found in the essential oil complex, p-cymol, thymoquinone and α-thuyen predominate. The hydrophilic fraction of the seeds of N. sativa L. includes flavonoids of the methoxylated series of flavones and kempferol glycosides.

This paper describes the synthesis of a nano-porous multilayered film consisting of Au@SiO2 nanoparticles. This film was used to miniaturize the size of a localized surface plasmon resonance (LSPR)-based capillary gas chromatograph (GC) detector. A layer-by-layer (LbL) approach with proper surface reaction sequences was used to create a multilayer structure that consisted of as many as five layers of Au@SiO2 nanoparticles. The center wavelength of LSPR was shifted from 520 to 634 nm due to the approximation of additional layers of nanoparticles. The vapor response time for this Au@SiO2 multilayer LSPR sensor was identical to that of an Au nanoparticle monolayer, which confirmed that this multilayer structure has a high level of gas permeability. The multilayer was synthesized inside a glass capillary for use as a GC detector. Due to the enhancement of absorbance, the gas chromatographic signal was obtained via a single spotlight that penetrated one side of the glass capillary and was then reflected by a silver mirror coated on the opposite side. The detection limits were ≤20 ng for cyclohexanone and m-xylene.

Forty-eight vinegar samples including white vinegar, rice vinegar and mature vinegar were collected from several markets in Beijing. Butyltin compounds were determined by headspace solid-phase microextraction coupled with gas chromatography and flame photometric detector after in situ ethylation with sodium tetraethylborate. Butyltin species were detected in sixteen vinegar samples and ranged from 0.012 to 14.10 μg Sn L−1. The detection rate of white vinegar is higher than that of rice vinegar and mature vinegar. Vinegar samples with relatively high butyltin concentration (>1.5 μg Sn L−1) were those stored in plastic bags, indicating that the plastic bag was one of the possible sources of butyltin contamination. This was further confirmed by the leaching experiments of three selected plastic bags, and monobutyltin was detected in the leaching solvents. According to the estimation, the average daily intake of total butyltin compounds through vinegar consumption is about 0.04 ng Sn/kg b.w., much lower than the Tolerable Daily Intake (TDI) of 100 ng Sn/kg b.w. set by the European Food Safety Authority (EFSA).