Reaction Gas Chromatography Research Articles

Application of post-column reaction gas chromatography with a single reference gas for offshore air and gas seeped from the seafloor samples.

Ambient air commonly contains carbon dioxide at concentrations greater than 400µmolmol-1 and methane at ~ 2000nmolmol-1; non-methane hydrocarbons are also widespread in the atmosphere at much lower concentrations. For quantification of various carbon-containing compounds in typical analytical instrument, corresponding number of reference materials are required. Therefore, the development of a method that uses a single reference material applicable to air monitoring is desired. Here, we examined a post-column reaction system combined with a gas chromatograph equipped with a flame ionization detector (FID), which involves oxidation and reduction processes after separation. To determine various carbon-containing gases by post-column reaction gas chromatography with FID (GC-r-FID) using a single reference, it is necessary to confirm a good linearity of the response with carbon concentrations originating from various carbon-containing gases. When mixtures of carbon-containing gases at three different concentrations and the calibration curve of the FID response with the concentration converted into methane were used, a single linear calibration curve (correlation coefficient > 0.9999, 18 points) was obtained over four orders of magnitudes (to ~ 5000µmolmol-1 as methane). The applicability of GC-r-FID was confirmed by determining carbon-containing gases in air and gas seeped from the seafloor samples. Because the results were comparable to those obtained by conventional GC-FID and GC-thermal conductivity detector, typically GC-r-FID with a single reference gas should be suitable for air monitoring.

Quantification of 23 Volatile Organic Compounds with a Single Reference Material Using Post-column Reaction Gas Chromatography Combined with a Stainless-steel Heating Furnace.

We built a heating furnace using stainless-steel instead of aluminum in gas chromatography combined with an oxidation/reduction system; it increased the oxidation temperature to 650°C. At 600°C, it completely oxidized five organochlorine compounds. This system was applied to a standard solution of 23 volatile organic compounds. The analytical results of 20 hydrocarbon and organochlorine compounds showed good agreement with the expanded uncertainty (k = 2) of the reference values. Three organobromine compounds obtained values higher than the reference; this was investigated further.

Determination of SI-Traceable Property Values of Volatile Organic Compounds in Samples by Using Post-Column Reaction Gas Chromatography

Determination of SI-Traceable Property Values of Volatile Organic Compounds in Samples by Using Post-Column Reaction Gas Chromatography

Phenazopyridine degradation by electro-Fenton process with magnetite nanoparticles-activated carbon cathode, artificial neural networks modeling

In this research, magnetite nanoparticles-activated carbon (MNP-AC) electrode was used as cathode through the electro-Fenton (EF) process to degrade Phenazopyridine (PhP). Graphite was used as anode and the reaction time was 120 min. The effects of main variables, including the applied current, initial pharmaceutical concentration, pH and magnetite nanoparticles (MNP) used as catalyst were investigated. PhP degradation efficiency observed for this method was 98.21% under optimum conditions (applied current = 0.2 A, [PhP]0 = 30 mg/L, pH = 3 and surface ratio of MNP/AC electrode 1:1). Scanning electron microscopy (SEM), Energy Dispersive X-Ray (EDX), X-ray diffraction (XRD) and Fourier-transform infrared spectroscopy (FT-IR) were performed for analyzing the structure of the electrodes. Oxygen reduction activity of the electrodes was examined by cyclic voltammetry (CV). Total organic carbon (TOC) was performed to investigate the PhP removal efficiency during the reaction time and Gas chromatography–mass spectrometry (GC–MS) were performed to analyze degradation by-products of PhP. In the presence of ethanol, the degradation efficiency of PhP was decreased to 54.34%. The PhP degradation efficiency was decreased about 6.93% after eight repeated runs. Based on the results, it was found this method can remove PhP from polluted water. To predict the performance of the degradation efficiency, artificial neural networks (ANN) model was established based on the experimental data.

Removal of Phenazopyridine from wastewater by merging biological and electrochemical methods via Azolla filiculoides and electro-Fenton process

In the present study, the potential of Azolla filiculoides (A. filiculoides) was first investigated for degradation of Phenazopyridine (PhP), an analgesic drug. The effects of main variables such as initial pharmaceutical concentration, amount of plant, and pH were studied on the efficiency of the biological process. It was observed that A. filiculoides was able to remove pharmaceuticals from contaminated water up to 85.90% during 48 h. Then, the electro-Fenton (EF) method was applied for further removal of PhP yielding a removal rate of about 98.72% under optimum conditions during 2 h. The effects of variables including the current, amount of catalyst, and pH were also studied in this phase. Also, the probability of adsorption was investigated during this step. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis were performed for the used magnetite nanoparticles, total organic carbon (TOC) were performed to investigate PhP removal efficiency during the reaction time and Gas chromatography–mass spectrometry (GC-MS) were performed to analyze degradation byproducts of PhP. Based on the results, it was found that a combination of these bioremediation and electrochemical removal steps were capable of PhP removal from contaminated water. Therefore, this approach may be effective for phytoremediation of pharmaceutical-contaminated aquatic ecosystems.

Conventional and new traceability schemes of organic standards for safe water supply in Japan

Metrological traceability to the International System of Units (SI) is required to ensure reliability of analytical results. For this purpose, SI-traceable standard solutions of respective analytes are essential for common analytical methods such as chromatography. However, it is not so easy to fulfill demands due to the existence of a vast number of targets, especially in the case of organic analysis. Because high-purity organic materials which are raw materials of standard solutions must be characterized by compound-independent methods, the mass balance approach (subtraction method) and the primary methods of measurement (e.g. the freezing point depression method and titrimetry) are used. Recently, quantitative NMR (qNMR) has been popularized.The National Metrology Institute of Japan, the National Institute of Advanced Industry, Science and Technology (NMIJ/AIST) has been supplying many types of reference materials including high-purity organic materials and organic standard solutions. In 2015, the demand of traceable reference materials for drinking water analyses rose by an amendment of a notification under the Waterworks Act of Japan. In this manuscript, NMIJ’s efforts such as supplying certified reference materials and providing calibration services in this field are outlined. Among them, direct characterization of multi-components standard solutions by qNMR/chromatography or post-column reaction gas chromatography is an efficient approach to realize new traceability schemes without the step of a purity assessment of each reference material.

Post-column reaction gas chromatography with a two-stage microreactor for the determination of volatile oxygenated compounds in high-pressure liquefied hydrocarbons

A reliable approach for the determination of volatile oxygenated compounds in high-pressure liquefied hydrocarbons with post-column reaction gas chromatography has been developed.

Application and Validation of a Determination Method Using Post-column Reaction Gas Chromatography of Nitrogen-containing Organic Compounds.

In this work, we applied post-column reaction gas chromatography (GC) using a flame ionization detector (FID) system to study nitrogen-containing organic compounds (NOCs). The results were subsequently validated. After separation by column, the target components were converted to carbon dioxide using an oxidizing catalyst and then reduced to methane, followed by detection using an FID. SI-traceable testing mixtures containing NOCs (isoprocarb, napropamide, and pendimethalin) were prepared by the gravimetric blending method. These mixtures were analyzed using a post-column reaction GC-FID system; standard materials of hydrocarbons were used as calibrants in this analysis. The determined values were compared with the values obtained for samples prepared at the corresponding concentrations, and statistical analyses were performed in all cases. It was shown that the determined and prepared values agreed well with each other within the uncertainty limits.

Towards the interaction between calcium carbide and water during gas-chromatographic determination of trace moisture in ultra-high purity ammonia

The current study focuses on the processes involved during the flow conversion of water into acetylene in a calcium carbide reaction cell for the trace moisture analysis of ammonia by reaction gas chromatography. The factors negatively affecting the reproducibility and the accuracy of the measurements are suggested and discussed. The intramolecular reaction of the HOCaCCH intermediate was found to be a side reaction producing background acetylene during the contact of wet ammonia gas with calcium carbide. The presence of the HOCaCCH intermediate among the reaction products is confirmed by an FTIR spectral study of calcium carbide powder exposed to wet gas. The side reaction kinetics is evaluated experimentally and its influence on the results of the gas chromatographic measurements is discussed in relation to the determination of the optimal operating parameters for ammonia analysis. The reaction gas chromatography method for the trace moisture measurements in an ammonia matrix was experimentally compared to an FTIR long-path length gas cell technique to evaluate the accuracy limitations and the resource intensity.

A critical assessment of transmethylation procedures for n-3 long-chain polyunsaturated fatty acid quantification of lipid classes

Lipid transmethylation methods described in the literature are not always evaluated with care so to insure that the methods are effective, especially on food matrix or biological samples containing polyunsaturated fatty acid (PUFA). The aim of the present study was to select a method suitable for all lipid species rich in long chain n-3 PUFA. Three published methods were adapted and applied on individual lipid classes. Lipid (trans)methylation efficiency was characterized in terms of reaction yield and gas chromatography (GC) analysis. The acid-catalyzed method was unable to convert triglycerides and sterol esters, while the method using an incubation at a moderate temperature was ineffective on phospholipids and sterol esters. On the whole only the method using sodium methoxide and sulfuric acid was effective on lipid classes taken individually or in a complex medium. This study highlighted the use of an appropriate (trans)methylation method for insuring an accurate fatty acid composition.

Simultaneous determination of aliphatic acids and aldehydes in aqueous media by reaction gas chromatography

A procedure is developed for the gas chromatographic determination of lower aldehydes as dibutoxyalkanes and carboxylic acids as butyl esters by the reaction with tributyl borate in an aqueous medium. Derivatization conditions were optimized. The procedure was used to determine side products in glyoxal synthesized by the catalytic oxidation of ethylene glycol.

Investigation of the Hydrogenation of 5-Methylfurfural by Noble Metal Nanoparticles in a Microcapillary Reactor.

On-column reaction gas chromatography (ocRGC) was successfully utilized as high-throughput platform for monitoring of the conversion and selectivity of hydrogenation of 5-methylfurfural catalyzed by polymer-stabilized Ru and Pd nanoparticles. We were able to elucidate the effect of various reaction conditions, mainly together with the catalyst loading on the conversion rate and the selectivity of the reaction. Our strategy yields significant improvements in reaction analysis times and cost effectiveness in comparison to standard methods. We are able to demonstrate that ocRGC approach provides valuable information about the reaction system that gives scientists a tool to design suitable catalytic systems for enhanced sustainable chemistry in the future.

ポストカラム反応ガスクロマトグラフィーを用いた炭化水素混合ガスに対する国際単位系にトレーサブルな値付け

ポストカラム反応ガスクロマトグラフィーを用いた炭化水素混合ガスに対する国際単位系にトレーサブルな値付け

Ambient measurements of aromatic and oxidized VOCs by PTR-MS and GC-MS: intercomparison between four instruments in a boreal forest in Finland

Abstract. Proton transfer reaction mass spectrometry (PTR-MS) and gas chromatography mass spectrometry GC-MS) are commonly used methods for automated in situ measurements of various volatile organic compounds (VOCs) in the atmosphere. In order to investigate the reliability of such measurements, we operated four automated analyzers using their normal field measurement protocol side by side at a boreal forest site. We measured methanol, acetaldehyde, acetone, benzene and toluene by two PTR-MS and two GC-MS instruments. The measurements were conducted in southern Finland between 13 April and 14 May 2012. This paper presents correlations and biases between the concentrations measured using the four instruments. A very good correlation was found for benzene and acetone measurements between all instruments (the mean R value was 0.88 for both compounds), while for acetaldehyde and toluene the correlation was weaker (with a mean R value of 0.50 and 0.62, respectively). For some compounds, notably for methanol, there were considerable systematic differences in the mixing ratios measured by the different instruments, despite the very good correlation between the instruments (mean R = 0.90). The systematic difference manifests as a difference in the linear regression slope between measurements conducted between instruments, rather than as an offset. This mismatch indicates that the systematic uncertainty in the sensitivity of a given instrument can lead to an uncertainty of 50–100 % in the methanol emissions measured by commonly used methods.

Comparison of a Molecular and an Immobilized Gadolinium(III)‐tris[(1R,4S)‐3‐heptafluorobutanoyl‐camphor] as Catalyst in the Asymmetric Danishefsky‐Hetero‐Diels‐Alder‐Reaction

On-column reaction gas chromatography combines the power of separation and rapid analysis of reactants and reaction products with screening of reactions in a single step. Not only conversions but the reaction rates at various temperatures can be obtained from single measurements, making this approach superior to the time-consuming measurements typically performed in reaction progress analysis. However, this approach has only been used in the investigation of interconversion processes, rearrangement reactions, and only a few examples of higher-order reactions are known. Here we present the screening of immobilized gadolinium(III)-tris[(1R,4S)-3-heptafluorobutanoyl-camphor] in the Danishefsky-hetero-Diels-Alder-reaction by enantioselective on-column reaction gas chromatography utilizing cryogenic focusing to achieve catalytic conversions in this higher-order reaction and subsequent separation of the enantiomeric product mixture to determine the enantiomeric ratio. The results obtained by this approach could be transferred to the conventional batch reaction at a larger scale, demonstrating that on-column reaction chromatography provides reliable results in the screening of enantioselective reactions.

Integrating reaction and analysis: investigation of higher-order reactions by cryogenic trapping.

A new approach for the investigation of a higher-order reaction by on-column reaction gas chromatography is presented. The reaction and the analytical separation are combined in a single experiment to investigate the Diels–Alder reaction of benzenediazonium-2-carboxylate as a benzyne precursor with various anthracene derivatives, i.e. anthracene, 9-bromoanthracene, 9-anthracenecarboxaldehyde and 9-anthracenemethanol. To overcome limitations of short reaction contact times at elevated temperatures a novel experimental setup was developed involving a cooling trap to achieve focusing and mixing of the reactants at a defined spot in a fused-silica capillary. This trap functions as a reactor within the separation column in the oven of a gas chromatograph. The reactants are sequentially injected to avoid undefined mixing in the injection port. An experimental protocol was developed with optimized injection intervals and cooling times to achieve sufficient conversions at short reaction times. Reaction products were rapidly identified by mass spectrometric detection. This new approach represents a practical procedure to investigate higher-order reactions at an analytical level and it simultaneously provides valuable information for the optimization of the reaction conditions.

Novel Method for the Determination of SI-Traceable Characteristic Values of Organic Standard Materials Using Reaction Gas Chromatography

トレーサビリティを確保し不確かさが付与された標準物質を開発するには，多くの時間と費用を必要とする．国際単位系（SI）にトレーサブルな標準物質の開発を簡易に行うことを目的として，反応による物質変換の技術を用いる研究を行い，新たな装置とその校正方法を開発した．ガスクロマトグラフ（GC）のカラム出口と水素炎イオン化検出器（FID）の間に酸化反応部と還元反応部を直列に組み込んだ装置では，優れた結果を得ることができた．この装置は，導入した試料成分をカラムで分離後，二酸化炭素に酸化し，直後にメタンへ還元しFIDで検出する．数種類のSIトレーサブルな標準物質を混合調製して本装置で測定し，メタン換算濃度とピーク面積値から関係線を求め直線となることで，反応系の反応効率を検証するとともに，装置の校正を行う．この関係線を用いて標準物質と異なる成分を含んだ試料を本装置で測定し，分離した成分すべての定量を行う．この新たな値付け法は，SIトレーサブルな標準物質の開発がより容易に行える画期的な方法である．

Formation of carbonyls and hydroperoxyenals (HPALDs) from the OH radical reaction of isoprene for low-NOx conditions: influence of temperature and water vapour content

The formation of gas-phase products from the reaction of OH radicals with isoprene for low-NOx conditions ([NOx] ≤ 1010 molecule cm−3) has been studied in an atmospheric pressure flow tube (Institute for Tropospheric Research-Laminar Flow Tube, IfT-LFT) operating in the temperature range of 293–343 K and a relative humidity of < 0.5 % up to 50 %. The photolysis of H2O2 or ozone photolysis in the presence of water vapour served as the NOx-free OH radical sources. For dry conditions at 293 K, the measured yields of methyl vinyl ketone (MVK), 0.07 ± 0.02, and methacrolein (MACR), 0.12 ± 0.04, were in reasonable agreement with literature data. Beside the C4-carbonyls, further product signals have been attributed tentatively to glycolaldehyde, methylglyoxal, hydroxyacetone, 3-methylfuran, C5-hydroperoxyenals (HPALDs) and C5-hydroxy-hydroperoxides. A simplified, “classical” reaction mechanism without efficient HPALD production describes well the observed yield for MVK and MACR. Unexpected high MVK and MACR yields of up to 0.65 in total were measured under conditions of a relative humidity of 50 % using both OH radical sources and two different measurement techniques for organics (proton transfer reaction mass spectrometry and gas chromatography with flame ionization detector). The reaction mechanism applied is not able to describe the strong increase of MVK and MACR yields with increasing water vapour content. The signal attributed to the HPALDs showed a distinct rise of about one order of magnitude increasing the temperature from 293 K to 343 K. A rough estimate leads to a HPALD yield of 0.32 at 343 K with an uncertainty of a factor of two. The results of this study do not support a predominant formation of HPALDs under atmospheric conditions in low-NOx areas. The surprisingly high MVK and MACR yields measured for a relative humidity of 50 % and the formation of glycolaldehyde, methylglyoxal and hydroxyacetone necessitate further research.

Gas-chromatographic determination of impurities of organic and chlorinated organic compounds and carbon monoxide and dioxide in high-purity hydrogen chloride

A gas-chromatographic procedure was developed for determining impurities (CH4, C2H6, C3H8, C4H10, iso-C4H10, C5H12, iso-C5H12, neo-C5H12, CH3Cl, C2H5Cl, CH2Cl2, CHCl3, CO, and CO2) in hydrogen chloride using two columns and a column switching technique in an isothermal mode with a flame ionization detector; the detection limits were 0.01–0.1 ppm. The matrix was separated in a precolumn packed with urea. CO and CO2 were determined by reaction gas chromatography with their conversion into methane.

Oxidations with bonded salen-catalysts in microcapillaries

Chiral vanadium(IV)–salen complexes with variable spacer length were immobilized on polysiloxanes, which were used as catalytically active stationary phase in on-column reaction gas chromatography, on-column reaction electrophoresis, in flow-through reactors and as coating of laboratory glassware. These devices modified with the catalytically active stationary phase were employed in asymmetric sulfoxidations using hydrogen peroxide as the oxidant. The here presented approach combines catalysis and chromatographic analysis in a single step and allows to study the kinetics of reactions and to optimize reaction conditions. The initial reaction kinetics and enantioselectivity of the sulfoxidation of benzylphenylsulfide was studied in dependency of the spacer length of the immobilized salen ligand. A drastic influence of the spacer length on the enantioselectivity in the here investigated sulfoxidation was measured.