Automated Gas Chromatography Research Articles

Organic fertilization reduces nitrous oxide emission by altering nitrogen cycling microbial guilds favouring complete denitrification at soil aggregate scale

Agricultural management practices can induce changes in soil aggregation structure that alter the microbial nitrous oxide (N2O) production and reduction processes occurring at the microscale, leading to large-scale consequences for N2O emissions. However, the mechanistic understanding of how organic fertilization affects these context-dependent small-scale N2O emissions and associated key nitrogen (N) cycling microbial communities is lacking. Here, denitrification gas (N2O, N2) and potential denitrification capacity N2O/(N2O + N2) were assessed by automated gas chromatography in different soil aggregates (>2 mm, 2–0.25 and <0.25 mm), while associated microbial communities were assessed by sequencing and qPCR of N2O-producing (nirK and nirS) and reducing (nosZ clade I and II) genes. The results indicated that organic fertilization reduced N2O emissions by enhancing the conversion of N2O to N2 in all aggregate sizes. Moreover, potential N2O production and reduction hotspots occurred in smaller soil aggregates, with the degree depending on organic fertilizer type and application rate. Further, significantly higher abundance and diversity of nosZ clades relative to nirK and nirS revealed complete denitrification promoted through selection of denitrifying communities at microscales favouring N2O reduction. Communities associated with high and low emission treatments form modules with specific sequence types which may be diagnostic of emission levels. Taken together, these findings suggest that organic fertilizers reduced N2O emissions through influencing soil factors and patterns of niche partitioning between N2O-producing and reducing communities within soil aggregates, and selection for communities that overall are more likely to consume than emit N2O. These findings are helpful in strengthening the ability to predict N2O emissions from agricultural soils under organic fertilization as well as contributing to the development of net-zero carbon strategies for sustainable agriculture.

Development of an Online Instrument for Continuous Gaseous PAH Quantification: Laboratory Evaluation and Comparison with The Offline Reference UHPLC-Fluorescence Method

Polycyclic aromatic hydrocarbons (PAHs) are widespread environmental contaminants formed during incomplete combustion or pyrolysis of organic material. The reliable quantification of PAH in airborne samples is still difficult, costly, and time-consuming due to the use of offline techniques, including long sampling on filters/adsorbents, laboratory extraction, purification, and concentration steps before analysis. To tackle these drawbacks, this work focused on the development of a fully automatic gas chromatograph (GC) equipped with a flame ionization detector (FID) and a sample preconcentration unit (PC) for gas sampling. This instrument was validated under laboratory-controlled conditions in the range 0–10 ng for 18 PAH. The chromatographic separation was rather satisfactory except for two PAH pairs, which were quantified together. For all compounds, the peak areas increased perfectly with the gaseous PAH concentration (R2 &gt; 0.98), without any significant memory effect between two consecutive analyses. Considering a gaseous sample volume of 1 L, the extrapolated limits of detections (LOD) were in the range 19.9–62.6 ng/m3, depending on the PAH. Its analytical performances were then compared to those of the offline reference UHPLC-fluorescence method, widely used for airborne PAH monitoring. This was also compared with the very few portable or continuously operating instruments.

Automated Gas Chromatography Peak Alignment: A Deep Learning Approach using Greedy Optimization and Simulation.

The clinical significance of volatile organic compounds (VOC) in detecting diseases has been established over the past decades. Gas chromatography (GC) devices enable the measurement of these VOCs. Chromatographic peak alignment is one of the important yet challenging steps in analyzing chromatogram signals. Traditional semi-automated alignment algorithms require manual intervention by an operator which is slow, expensive and inconsistent. A pipeline is proposed to train a deep-learning model from artificial chromatograms simulated from a small, annotated dataset, and a postprocessing step based on greedy optimization to align the signals.Clinical Relevance- Breath VOCs have been shown to have a significant diagnostic power for various diseases including asthma, acute respiratory distress syndrome and COVID-19. Automatic analysis of chromatograms can lead to improvements in the diagnosis and management of such diseases.

An autonomous remotely operated gas chromatograph for chemically resolved monitoring of atmospheric volatile organic compounds

An automated gas chromatography flame ionization detector with automated calibration and data analysis enabling long-term VOC monitoring.

Variability and sources of NMHCs at a coastal urban location in the Piraeus Port, Greece

Ambient concentrations and sources of non-Methane Hydrocarbons (NMHCs) with 6–9 carbon atoms were investigated at an industrialized coastal location within the Port of Piraeus in Greece. Measurements were performed for a yearlong period during 2019 by means of an automated gas chromatograph with flame ionization detector (GC-FID). N-Hexane registered the highest annual mean concentration, followed by toluene and benzene, whereas all compounds presented important day to day variability, with an enhancement in summer. The seasonal diurnal cycles were characterized by strong morning peaks, especially in summer. The night-time maxima were less pronounced during the warm period, by almost 50% relative to the morning ones. On the contrary, during winter night-time, the combined impact of emissions and the shallow boundary layer was reflected on the night-time peaks. The area seems to be affected mainly by local land emission sources, whereas temperature possibly triggers evaporation processes, as indicated by comparisons with nearby traffic and urban background sites. The enhanced NMHCs concentration, in spite of increased ventilation coefficients during the summer, indicated again the impact of local emission sources. This was also highlighted by means of Positive Matrix Factorization (PMF) modeling. Three PMF factors were identified, quantified and supported by supplementary seasonal runs during short-term campaigns. Fugitive emissions were recognized as the main source, contributing more than 70% of total NMHCs year-round, while the input of emissions associated with traffic and diesel combustion was almost equal (13% and 15%, respectively).

Influence of seasonal variability on source characteristics of VOCs at Houston industrial area

We studied the seasonal variations of volatile organic compounds (VOCs) in the Houston metropolitan area in the summertime and wintertime of 2018. The analysis of hourly measurements obtained from the automated gas chromatograph (auto-GC) network showed the total VOC average concentrations of 28.68 ppbC in the summertime and 33.81 ppbC in the wintertime. The largest contributions came from alkane compounds, which accounted for 61% and 82% of VOCs in the summer and winter, respectively. We performed principal component analysis (PCA) and Positive Matrix Factorization (PMF) and identified seven factors in the summertime and six factors in the wintertime, among which alkane species formed three factors according to their rate of reactions in both seasons: (1) the emissions of long-lived tracers from oil and natural gas (ONG long-lived species), (2) fuel evaporation, and (3) the emissions of short-lived tracers from oil and natural gas (ONG short-lived species). Two other similar factors were (4) emissions of aromatic compounds and (5) alkene species of ethylene and propylene. Summertime factor 6 was associated with acetylene, and one extra summertime factor 7 was influenced by the biogenic emissions. The factor 6 of wintertime was affected by vehicle exhaust. Higher nighttime and lower daytime values of the ethylene/acetylene ratios indicated a stronger rate of photochemical degradation during the summertime. Higher reactivities of alkenes and aromatics with radicals make seasonal differences of these compounds less variant. Also, the exploration of the photochemical processes of the VOCs showed that the ethylene and propylene had the highest contributions to the summertime and wintertime ozone formation as well as the emissions of the isoprene, which showed a high impact on summertime ozone. Our results acknowledged that ethylene and propylene continue to be significant emissions of VOCs, and their emissions control would help the mitigation of the ozone problem in downwind areas related to emissions at the Houston Ship Channel (HSC). Based on trajectory analysis, we localized the main VOC emission sources in HSC near local industrial areas and regions south of the HSC. Ambient concentrations of VOC in both seasons revealed compounds that measured at the HSC were influenced by the emissions from the petrochemical sectors and industrial complexes, especially from the Baytown refinery and Bayport industrial district next to the HSC and Galveston Bay refineries at the south of the study area.

Nitrite accumulation and impairment of N2O reduction explains contrasting soil denitrification phenotypes

Soil denitrification produces the potent greenhouse gas and ozone depleter nitrous oxide (N2O). We previously linked soil N2O emission potential (N2O/N2O + N2) to a continuum of denitrification phenotypes in 20 pasture soils but were unable to determine their proximal cause. At one end of the continuum, soils carried out completely concurrent production and reduction of N2O (concurrent phenotype) while at the other end soils delayed N2O reduction until almost all added nitrate (NO3−) was accumulated as N2O (sequential phenotype). In an unsealed environment, the later phenotype is predicted to emit most added N as N2O. Here we tested the role of delayed N2O reductase synthesis and nitrite (NO2−) based impairment of N2O reduction as determinants of delayed N2O reduction in soils with sequential phenotypes. Nitric oxide (NO), N2O and N2 accumulation were measured in response to added NO3−, NO2− and N2O in anoxic batch incubations of fresh or pre-incubated soil using automated gas chromatography. Successive NO3− additions drove 6 of 7 soils towards increasingly concurrent N2O production/reduction, suggesting delayed production of N2O reductase may be the cause of delayed N2O reduction in initially sequentially denitrifying soils. NO2− addition (2 mM NO3− + 1 mM NO2− vs. 3 mM NO3− control) to sequentially and concurrently denitrifying soil demonstrated that NO2− impairs N2O reduction, even when N2O reductase was fully induced (pre-incubated soils, 1 mM NO2− + 42 μmol N2O vs. 42 μmol N2O control). Further, 2 pieces of evidence suggest that differences in NO2− accumulation are a probable cause of the previously observed denitrification phenotypes. 1) 48 fold higher NO2− accumulation in the sequential vs. concurrent soil in response to 3 mM NO3− addition. 2) the concurrent timing of NO2− depletion/N2O reduction in the sequential soil. However, these observations should be confirmed in a greater number of soils. Inhibition of N2O reductase by NO is proposed as a potential proximal cause of impaired early N2O reduction which could link separate effectors (NO2−, carbon, successive NO3− additions) to a common inhibitory mechanism.

Development of Flowerlike Ce1-XZrxO2-δ-Dispersed Paper-Structured Catalyst for Direct-Biogas SOFC

Performance of direct internal reforming (DIR)-solid oxide fuel cell (SOFC) can be improved by the application of the paper-structured catalyst (PSC) on the anode material. In the ceramic fiber network of the PSC, any kinds of functional materials can be easily dispersed during paper-making process.The solid solution based on the equimolar mixture of ceria and zirconia (Ce0.5Zr0.5O2-δ), hereafter called CZ, is a promising oxide support of the Ni metal catalyst due to its high specific surface area and high oxygen storage capacity (OSC). By employing the two-step hydrothermal process developed in this study, we could successfully prepare the CZ with flowerlike geometry, which can prevent Ni from sintering under reducing atmosphere.Ni-loaded PSCs with and without the dispersion of CZ, Ni/CZ-PSC and Ni-PSC, respectively, were prepared. Structures of the PSCs were characterized by X-ray diffractometry (XRD), BET specific surface area measurement, field emission scanning electron microscopy (FESEM), inductively coupled plasma spectrometry (ICP) and thermogravimetric analysis (TG). Catalytic performances of these PSCs for the dry reforming of methane (DRM) in the feed of the equimolar mixture of CH4 and CO2 were evaluated by an automatic gas chromatograph (GC) with the posttest analysis by FESEM observation, temperature-programmed oxidation (TPO) and TG to estimate carbon deposition.In the durability (160 h) tests of the prepared-PSCs for DRM at 750oC under gas hourly space velocity (GHSV) of 2300 h-1 revealed that, for both cases with and without CZ dispersion, methane conversions were stable with the degradation rates (estimated after 10 h) of 13.7 and 21.8% 1000 h-1, respectively. TG measurements after the 160 h tests under oxidizing atmosphere in the range from 300 to 750oC revealed that the weights of the deposited carbon were 0.2 and 3.4 folds of those of PSCs for Ni/CZ-PSC and Ni-PSC, respectively. In the case without CZ dispersion (Ni-PSC), after the TG measurement to burn out the deposited carbon, Ni agglomeration and its detachment from the ceramic fiber could be clearly observed. On the other hand, for the Ni/CZ-PSC, these phenomena were considerably suppressed thanks to the flowerlike morphology for better dispersion of Ni metal particles and higher OSC of CZ solid solution to consume deposited carbon by the lattice oxygen.The developed PSCs will be applied on the anode of electrolyte-supported cell to demonstrate the stable operation of DIR-SOFC fueled by biogas (direct-biogas SOFC).

Indicators of volatile fatty acids for differential diagnostics of nfected of pancreatic necrosis complicated by retroperitoneal phlegmon.

The aim of the study was to assess the informative value of volatile fatty acid parameters for the differential diagnosis of infected pancreatic necrosis (IPN), complicated by retroperitoneal cellulitis. The work was based on the results of examination and treatment of 44 patients with infected pancreatic necrosis. The analysis of concentrations of volatile fatty acids: acetic, propionic, butyric and isovalerianic was carried out on a Kristallux-4000 automated gas chromatograph with an HP-FFAP capillary column and a flame ionization detector. The indicators of acetic acid and the amount of volatile fatty acids were statistically significantly higher in patients with infected pancreatic necrosis with total retroperitoneal phlegmons in comparison with the indicators of volatile fatty acids in patients with infected pancreatic necrosis with paracolic phlegmons and in comparison with indicators of volatile fatty acids in patients with infected pancreatic necrosis phlegmons. The indicators of acetic acid and the amount of VFA can be used as additional criteria for the differential diagnosis of IPN complicated by phlegmons of the retroperitoneal tissue.

Soil N2O emission potential falls along a denitrification phenotype gradient linked to differences in microbiome, rainfall and carbon availability

Soil denitrification produces the potent greenhouse gas nitrous oxide (N2O) and by further reduction of N2O, the harmless inert gas N2. N2O emission is determined by rate and timing of the N2O producing and reducing steps which are sensitive to a series of proximal and distal regulators such as pH and microbial community composition. Microbial community associations to N2O emission potential (N2O/(N2O + N2)) are commonly entangled with pH leaving the true role of community composition unclear. Here, we leverage a set of soil microbiomes strongly linked to rainfall above pH to test the hypothesis that microbiome vs. N2O emission potential (N2O/(N2O + N2)) correlations will be maintained across alternative distal drivers. N2O emission potential (N2O/(N2O + N2)) and denitrification gas (NO, N2O, N2) kinetics were assessed by automated gas chromatography while community composition was assessed by 16 S rRNA gene sequencing and qPCR of nosZI and II genes. Analyses revealed a sustained correlation between microbiome and N2O emission potential (N2O/(N2O + N2)) in the absence of a pH effect. Further, a continuum of gas accumulation phenotypes linked to NO accumulation and sensitive to carbon addition are identified. Separate phenotypes carried out N2O production and reduction steps more concurrently or sequentially and thus determined N2O accumulation and emission potential (N2O/(N2O + N2)). Concurrent N2O producing/reducing soils typically contained NO accumulation to a low steady state, while carbon addition manipulations which increased NO accumulation also increased sequentiality of N2O production/reduction and thus emission potential (N2O/(N2O + N2)). These features may indicate a conserved NO inhibitory mechanism across multiple effectors (rainfall, community composition, carbon availability).

Development and Validation of an Automated Gas Chromatography Method for Determination of Dichloromethane in Ampicillin Sodium by Using Capillary Column Technology

Background: The main aim of the study was to develop an automated static headspace gas chromatography (SHS-GC) method for determination of dichloromethane (DCM) in ampicillin sodium by using a capillary column. Methods: SHS-GC also known as gas chromatography-headspace is the technique of choice due to its high sensitivity, excellent separation abilities, low limit of detection and simplicity of the instrumentation used for the technique. The headspace sampling method has more appropriate sensitivity than the direct injection method because it can clearly separate volatile analytes from the sample matrix and effectively concentrate them. Therefore, this method results in less complex sample preparation, decreased instrument contamination, and increased capillary column life. Results: The developed SHS-GC method showed symmetrical peak shape reasonable retention time for DCM. A linear relationship was obtained over the range of 2-240 μg mL-1 with a correlation coefficient (r2) of 0.993. The recovery, system precision and robustness of the method were within the acceptable values. The Limit of Detection (LOD) and Limit of Quantitation (LOQ) were 0.5 μg mL-1 and 2 μg mL-1 respectively. Conclusions: The results obtained in this study demonstrate that SHS-GC method is selective, precise, linear, accurate and robust for determination of dichloromethane in ampicillin sodium and its formulation (injection).

Formation-Fluid Microsampling While Drilling Enables Complete Reservoir Characterization

This article, written by JPT Technology Editor Judy Feder, contains highlights of paper SPE 195806, “Formation-Fluid Microsampling While Drilling: A New PVT and Geomechanical Formation-Evaluation Technique,” by Julia Golovko, Christopher Jones, SPE, and Bin Dai, Halliburton, et al., prepared for the 2019 SPE Annual Technical Conference and Exhibition, Calgary, 30 September-2 October. The paper has not been peer reviewed. Pressure/volume/temperature (PVT) phase behavior characterization and geochemical compositional analysis of petroleum samples play a crucial role in the determination of producible reserves and the best production strategy. Openhole samples are the most-valuable types of samples for PVT and geochemical analysis but are costly and limited to 10 to 20 samples. The complete paper presents a technical discussion of a new microsampling technique for logging while drilling (LWD) and a corresponding wellsite technique to provide compositional interpretation, contamination assessment, reservoir-fluid compositional grading, and reservoir compartmentalization assessment. This microscale approach enables fast analysis by using field or near-field deployment of the analytical tool. The results inform planning for wireline sample retrieval, if necessary. Technique Overview The microsampler used in the downhole tool can collect reservoir fluid in small quantities suitable for compositional analysis. Because of its small size, the microsampler can gather multiple fluids at various reservoir depths, while PVT sampling requires larger volumes and has more constraints. However, when used in combination with conventional PVT-grade samples, the microsamples can provide significant chemical profiling. The 40-ml quantity provides the ability to collect many more samples than the conventional PVT sample size of 200 to 1,000 ml. Additionally, 40 ml provides more than enough of a sample for a complete chemical analysis using a liquid chromatograph or gas chromatograph coupled with either a mass spectrometer for biomarker analysis or a flame-ionization detector (FID) for a complete assay. Isotope analysis is also possible. Recovery to surface of fluid samples collected at reservoir temperature and pressure allows for analysis with an automated gas chromatograph (GC) deployed in the field, providing reduced labor and rapid analysis. The unique injection chamber of the GC is designed with the injection port and valve configured to withstand pressure up to 5,000 psi, a tolerance approximately five times higher than that of standard GC injection valves. This allows for injection of the microsample with a solvent carrier as a single-phase fluid so that analysis can provide composition and fluid properties such as gas/oil ratio without a flash. The GC has two detectors, including an FID for hydrocarbon components and a thermal conductivity detector for inorganic gas components such as carbon dioxide, nitrogen, and hydrogen sulfide. The system can quantify hydrocarbon components from C1 to C36 and perform contamination studies of oil samples with drilling fluids. According to the authors, the technique enables reservoir engineers to characterize a reservoir completely without limit to the number of acquired samples. They write that, in combination with conventional PVT samples, it is possible to extrapolate PVT properties to all pump-out stations and conduct a complete geochemical profile of the reservoir.

Comparison of carcass and meat quality traits between lean and fat Pekin ducks.

ObjectiveAccording to market demand, meat duck breeding mainly includes 2 breeding directions: lean Pekin duck (LPD) and fat Pekin duck (FPD). The aim of the present study was to compare carcass and meat quality traits between 2 strains, and to provide basic data for guidelines of processing and meat quality improvement.MethodsA total of 62 female Pekin ducks (32 LPDs and 30 FPDs) were slaughtered at the age of 42 days. The live body weight and carcass traits were measured and calculated. Physical properties of breast muscle were determined by texture analyzer and muscle fibers were measured by paraffin sections. The content of inosine monophosphate (IMP), intramuscular fat (IMF) and fatty acids composition were measured by high-performance liquid chromatography, Soxhlet extraction method and automated gas chromatography respectively.ResultsThe results showed that the bodyweight of LPDs was higher than that of FPDs. FPDs were significantly higher than LPDs in subcutaneous fat thickness, subcutaneous fat weight, subcutaneous fat percentage, abdominal fat percentage and abdominal fat shear force (p<0.01). LPDs were significantly higher than FPDs in breast muscle thickness, breast muscle weight, breast muscle rate and breast muscle shear force (p<0.01). The muscle fiber average area and fiber diameter of LPDs were significantly higher than those of FPDs (p<0.01). The muscle fiber density of LPDs was significantly lower than that of FPDs (p<0.01). The IMF of LPDs in the breast muscle was significantly higher than that in the FPDs (p<0.01). There was no significant difference between the 2 strains in IMP content (p>0.05). The polyunsaturated fatty acid content of LPDs was significantly higher than that of FPDs (p<0.01), and FPDs had higher saturated fatty acid and monounsaturated fatty acid levels (p<0.05).ConclusionLong-term breeding work resulted in vast differences between the two strains Pekin ducks. This study provides a reference for differences between LPD and FPD that manifest as a result of long-term selection.

INDICATORS OF VOLATILE FATTY ACIDS IN DIFFERENTIAL DIAGNOSTICS OF INFECTED AND STERILE PANCREONECROSIS

The aim of the study was to assess the information content of volatile fatty acid parameters for the differential diagnosis of infected and sterile pancreatic necrosis. The work is based on the results of examination and treatment of 34 patients with pancreatic necrosis. The analysis of concentrations of volatile fatty acids: acetic, propionic, butyric and isovaleric was carried out on an automated gas chromatograph «Crystallux-4000» with a capillary column «HP-FFAP» and flame ionization detector. The indicators of acetic, propionic, butyric, isovaleric acid and the sum of volatile fatty acids are statistically significantly higher in patients with infected pancreatic necrosis compared with the indicators of volatile fatty acids in patients with sterile pancreatic necrosis. Volatile fatty acid values can be used for the differential diagnosis of infected and sterile pancreatic necrosis.

Evidence of variations of endogenous halogenated volatile organic compounds in alveolar breath after mental exercise-induced oxidative stress

The effect of oxygen on markers of oxidative stress has not been totally elucidated because previous studies have yielded conflicting results. A method for the collection and gas chromatography-mass spectrometry of the halogenated volatile organic compounds in human alveolar breath is described. A transportable apparatus sampled specifically alveolar breath; the volatile organic compounds were captured in a thermal desorption tube, Carbotrap 200®. The sample was thermally desorbed from the trap in an automated gas chromatography with mass spectrometry detection and peak fragmentation. Compounds were identified by reference to a computer-based library of mass spectra. Trichlorotrifluoroethane, tetrafluoroethane, dichlorodifluoromethane were identified in alveolar breath of healthy volunteers after mental exercise-induced oxidative stress. The effects of halogenated alkanes were investigated on electron transport chain activity. These agents impaired the NADH oxidation suggesting an inhibition of the complex I (NADH: ubiquinone oxidoreductase) of the electron transport chain. These inhibitory effects are suspected likely to fight against oxidative stress deleterious reactions. Chemical inhibition of the oxidative burst in human body trough these halogenated inhibitors is a new concept of significant practical, medical, biological and scientific interest.

A comparative study of volatile fatty acids in the blood and in the drainage from pancreatic fistula in pancreatic necrosis

Relevance. The informative value of the content of volatile fatty acids (VFA) in the fistulous drainage from pancreas not been studied in the diagnosis of pancreonecrosis (PN). The informative value of the indices of the content of VFA in the blood has not been studied sufficiently in the diagnosis of PN.&#x0D; Aim of the study is to compare the content of VFA in the blood and in the fistulous drainage from pancreas in patients with pancreatic necrosis.&#x0D; Materials and methods. Samples of blood and fistulous drainage from pancreas isolated from patients with a confirmed diagnosis of PN were studied (n = 18). There was analysis of the concentrations of VFA: acetic, propionic, butyric and isovaleric acids by gas-liquid chromatography on an automated gas chromatograph "Crystallux-4000" with a capillary column "HP-FFAP" Agilent Technologies and a flame ionization detector. The anaerobic index and sum of VFA were calculated.&#x0D; Results. Higher values of the content of acetic, propionic and butyric acids, the sum of VFA and lower values of the content of isovaleric acid and anaerobic index were found in patients with PN in comparison with those of practically healthy donors. Higher values of the content of acetic, propionic and isovaleric acid, the sum of VFA and anaerobic index were noted in the fistulous drainage from pancreas in comparison with the same parameters in blood in patients with PN. The correlation of pairwise conjugated parameters of the content of propionic and isovaleric acids, anaerobic index and the sum of VFA in fistulous drainage from pancreas and blood are discovered in patients with PN.&#x0D; Conclusions. The concentration of acetic, propionic and isovaleric acids, the sum of VFA were higher in the fistulous drainage from pancreas than in the blood in patients with PN. The analysis of the parameters of the VFA can be used as additional criteria for the early diagnosis of PN.

Continuous Measurement of Odorant Composition for Liquefied Petroleum Gas

In Chile, commercial liquefied petroleum gas (LPG) is customarily odorized with dimethyl sulfide (DMS) and tert-butyl mercaptan (TBM) at a rate of about 10 grams of odorant per 1 cubic meter of LPG. The current control of the odorization practice involves the human nose to detect the odor in some cases, and the determination of total sulfur concentration in others. None of those methods provide the speciation of the sulfur species in LPG.On the other hand, both DMS and TBM are higher boiling than propane or butane. Therefore, the odorant concentration emanating from the odorized liquid is not uniform in the vapors released. Furthermore, the gas will also be much leaner than the odorized liquid. For those reasons, the Chilean industry recommends analyzing the odorant directly from the liquid phase.To address the problem of odorant quantification at the industry this research aims to develop a reliable and objective measure for odorized LPG that allow not only verify the odorization itself but also quantify the species incorporated with the fuel, and other sulfur compounds present naturally in the LPG. In this regard, an Automated Gas Chromatograph (Auto-GC) with an electrochemical detector was coupled with an LPG valve, which continuously takes samples of 1 µL of liquid propane. The extracted sample is then vaporized and injected into the Auto-GC to be analyzed.The methodology is capable of distinguishing and quantifying distinct odorants near real-time (within 8 minutes), as well as other sulfur impurities present in the LPG such as tetrahydrothiophene (THT) and methyl mercaptan (MeSH). Typical retention times for TBM and DMS corresponded to 282 s and 418 s respectively. More importantly, the proposed method provides meaningful information to verify the optimum odorization, i.e., the minimum value to alert in case of leak and maximum level that assures efficient combustion.

Parallel online determination of ethylene release rate by Shaken Parsley cell cultures using a modified RAMOS device

BackgroundEthylene is an important plant hormone that controls many physiological processes in plants. Conventional methods for detecting ethylene include gas chromatographs or optical mid-infrared sensors, which are expensive and, in the case of gas chromatographs, are hardly suitable for automated parallelized online measurement. Electrochemical ethylene sensors are cheap but often suffer from poor resolution, baseline drifting, and target gas oxidation. Thus, measuring ethylene at extremely low levels is challenging.ResultsThis report demonstrates the integration of electrochemical ethylene sensors into a respiration activity monitoring system (RAMOS) that measures, in addition to the oxygen transfer rate, the ethylene transfer rate in eight parallel shake flasks. A calibration method is presented that is not prone to baseline drifting and considers target gas oxidation at the sensor. In this way, changes in ethylene transfer rate as low as 4 nmol/L/h can be resolved. In confirmatory experiments, the overall accuracy of the method was similar to that of gas chromatography-mass spectrometry (GC/MS) measurements. The RAMOS-based ethylene determination method was exemplified with parsley suspension-cultured cells that were primed for enhanced defense by pretreatment with salicylic acid, methyl jasmonate or 4-chlorosalicylic acid and challenged with the microbial pattern Pep13. Ethylene release into the headspace of the shake flask was observed upon treatment with salicylic acid and methyl jasmonate was further enhanced, in case of salicylic acid and 4-chlorosalicylic acid, upon Pep13 challenge.ConclusionA conventional RAMOS device was modified for simultaneous measurement of the ethylene transfer rate in eight parallel shake flasks at nmol/L/h resolution. For the first time electrochemical sensors are used to provide a medium-throughput method for monitoring ethylene release by plants. Currently, this can only be achieved by costly laser-based detection systems and automated gas chromatographs. The new method is particularly suitable for plant cell suspension cultures. However, the method may also be applicable to intact plants, detached leaves or other plant tissues. In addition, the general principle of the technology is likely extendable to other volatiles or gases as well, such as nitric oxide or hydrogen peroxide.

Understanding unusually high levels of peroxyacetyl nitrate (PAN) in winter in Urban Jinan, China

Peroxyacetyl nitrate (PAN), as a major secondary pollutant, has gained increasing worldwide attentions, but relevant studies in China are still quite limited. During winter of 2015 to summer of 2016, the ambient levels of PAN were measured continuously by an automatic gas chromatograph equipped with an electron capture detector (GC–ECD) analyzer at an urban site in Jinan (China), with related parameters including concentrations of O3, NO, NO2, PM2.5, HONO, the photolysis rate constant of NO2 and meteorological factors observed concurrently. The mean and maximum values of PAN concentration were (1.89 ± 1.42) and 9.61 ppbv respectively in winter, and (2.54 ± 1.44) and 13.47 ppbv respectively in summer. Unusually high levels of PAN were observed during severe haze episodes in winter, and the formation mechanisms of them were emphatically discussed. Study showed that high levels of PAN in winter were mainly caused by local accumulation and strong photochemical reactions during haze episodes, while mass transport played only a minor role. Accelerated photochemical reactions (compared to winter days without haze) during haze episodes were deduced by the higher concentrations but shorter lifetimes of PAN, which was further supported by the sufficient solar radiation in the photolysis band along with the high concentrations of precursors (NO2, VOCs) and HONO during haze episodes. In addition, significant PAN accumulation during calm weather of haze episodes was verified by meteorological data.

Comparison of optical-feedback cavity-enhanced absorption spectroscopy and gas chromatography for ground-based and airborne measurements of atmospheric CO concentration

Abstract. We present the first comparison of carbon monoxide (CO) measurements performed with a portable laser spectrometer that exploits the optical-feedback cavity-enhanced absorption spectroscopy (OF-CEAS) technique, against a high-performance automated gas chromatograph (GC) with a mercuric oxide reduction gas detector (RGD). First, measurements of atmospheric CO mole fraction were continuously collected in a Paris (France) suburb over 1 week. Both instruments showed an excellent agreement within typically 2 ppb (part per billion in volume), fulfilling the World Meteorological Organization (WMO) recommendation for CO inter-laboratory comparison. The compact size and robustness of the OF-CEAS instrument allowed its operation aboard a small aircraft employed for routine tropospheric air analysis over the French Orléans forest area. Direct OF-CEAS real-time CO measurements in tropospheric air were then compared with later analysis of flask samples by the gas chromatograph. Again, a very good agreement was observed. This work establishes that the OF-CEAS laser spectrometer can run unattended at a very high level of sensitivity ( &lt; 1 ppb) and stability without any periodic calibration.