Ionization Detection System Research Articles

Results from the development of ionization detection systems for the DRAGON facility

We discuss the implementation of an ionization detection system for the focal plane of the DRAGON recoil mass separator. We report recent tests performed with stable beams to test the feasibility of such a system for use in measurements of radiative capture reactions in inverse kinematics with radioactive beams.

Column switching–back flushing technique for the analysis of aromatic compounds in gasoline

A simple method, based on the technique of capillary column switching–back flushing, has been developed for the detailed analysis of aromatic compounds in gasoline. The sample was first separated on a 30-m long OV-2330 polar precolumn and then backflushed onto a nonpolar analytical column. The early eluting components from the precolumn and the components of interest (aromatic compounds plus heavier compounds) eluting from the analytical column are all directed to the same flame ionization detection system through a T piece, which permits the quantitative analysis of aromatic hydrocarbons in gasoline by a normalization method using correcting factors. The switching time window of the method is ±5 s, resulting in easier operation and higher reliability. The reproducibility of the quantitative analysis was ≤3% RSD for real gasoline samples.

Plant physiological influences on the fluxes of oxygenated volatile organic compounds from ponderosa pine trees

Fluxes of oxygenated volatile organic compounds were measured above a ponderosa pine plantation, adjacent to the Blodgett Forest Research Station (38°53′42.9″N, 120°37′57.9″W, 1315 m elevation), with a fully automated relaxed eddy accumulation system coupled to a dual gas chromatograph‐flame ionization detector (GC‐FID) system. These measurements were initially reported by Schade and Goldstein [2001]. Here we further analyze these data to explore the physiological controls on emissions of 2‐methyl‐3‐buten‐2‐ol (MBO), ethanol, and acetaldehyde. Measured MBO fluxes were compared to fluxes predicted by a detailed leaf‐level emission model. Although the match was very good in general, the model failed to predict a declined emission potential on cooler days following a very cold night. It also consistently overpredicted fluxes in the morning, while underpredicting fluxes in the afternoon, particularly on warm days. We conclude that the ponderosa pine MBO emission potential changes in response to recent environmental temperatures on diurnal and daily timescales, similar to changes reported for isoprene emissions. Though ambient temperature appeared to be the most important driver of ethanol and acetaldehyde fluxes, vapor pressure deficit strongly influenced ethanol emissions from ponderosa pine, suggesting that stomatal opening impacts emissions. Ethanol emissions were also found to increase after high ozone deposition fluxes, which supports the theory that ozone‐induced stress may trigger fermentation processes in the leaves.

C 2–C 8 Hydrocarbon measurement and quality control procedures at the Global Atmosphere Watch Observatory Hohenpeissenberg

A new automated on-line GC–flame ionization detection system for long-term stationary measurements of atmospheric C 2–C 8 hydrocarbons in the lower ppt range is described. The system is operated at the Global Atmosphere Watch Observatory Hohenpeissenberg (47°48′N, 11°01′E) in rural south Germany. Atmospheric mixing ratios of more than 40 different hydrocarbons can be continuously measured in 80 min time intervals. Corresponding detection limits are below 3 ppt, except for propene, butenes and benzene (about 10 ppt). Detailed quality assurance and quality control protocols are described which are applied to routine operation and data analysis. The various error contributions, overall precision, and accuracy for all measured compounds are discussed in detail. Typical ambient air mixing ratios are in the range of a few ppt to a few ppb, and corresponding measurement accuracies are below 10% or 10 ppt. For less than 20% of the analyzed compounds measurement accuracies are worse, mainly because of insufficient peak separation, blank values or reduced reproducibilities. The present system was tested in international intercomparison experiments (NOMHICE, AMOHA). For most of the C 2–C 8 hydrocarbons analyzed, our results agreed better than ±10% (20% NOMHICE phase 5) or ±10 ppt with the corresponding reference values.

Prediction of relative response factors for flame ionization and photoionization detection using self-training artificial neural networks

The relative response factors (RRFs) of a flame ionization detection (FID) system and two pulsed discharge photoionization detection (PID) systems with different discharge gases are predicted for a set of organic compounds containing various functional groups. As a first step, numerical descriptors were calculated based on the molecular structures of compounds. Then, multiple linear regression (MLR) was employed to find informative subsets of descriptors that can predict the RRFs of these compounds. The selected MLR model for the FID system includes seven descriptors and two selected MLR models for the PID systems with argon- and krypton-doped helium as the discharge gases, respectively, include six and five descriptors. The descriptors appearing in the MLR models were considered as inputs for the self-training artificial neural networks (STANNs). A 7-7-1 STANN was generated for prediction of RRFs of the FID system, and two STANNs with the topologies of 6-7-1 and 5-6-1 were generated for the two PID systems. Comparison of the results indicates the superiority of neural networks over that of the MLR method. This is due to the nonlinear behaviors of relative response factors for all type of detectors studied in this work.

Monitoring of fluorine in urine samples of patients involved in the Tokyo sarin disaster, in connection with the detection of other decomposition products of sarin and the by-products generated during sarin synthesis

We developed a new assay method for fluoride anion (F −) a specific metabolite of sarin. Trimethyifluorosilane (TMFS) was derivatized from F − with trimethylsilanol, and TMFS was detected with a GC–flame ionization detector (FID) and capillary column system. The linear range, detection limit and recovery rate were 0.02–10 ppm, 0.01 ppm and 97.3–103.0%, respectively. The patients were reported to be exposed only once to the toxic substance (a bolus exposure). F − excretion in urine of the hospitalized patients demonstrated three or four peaks. Other common metabolites of sarin and by-products such as methylphosphonic acid (MPA) and isopropyl alcohol (IPA) also showed two or three peaks. These results suggested that the patients were exposed to not only sarin but also fluoride and isopropyl alcohol containing by-products. The sum of MPA excreted was 0.3–90 mM, far exceeding the human lethal dose of sarin. The residual acetyicholine esterase activity of erythrocytes on admission (4.7–57.2% of the individual reference value) of the patients showed statistically significant relationships only with the initial values of F − and the isopropyl methylphosphonate. This evidence also suggested the exposure to fluoride and isopropyl alcohol-containing by-products.

High-resolution gas-chromatographic analysis of the secondary metabolites obtained by subcritical-fluid extraction from Colombian rue ( Ruta graveolens L.)

Subcritical (CO 2) extraction, carried out in a J&W Scientific High Pressure Soxhlet Extractor, was used to isolate secondary metabolites from leaves, flowers, stems and roots of Colombian rue ( Ruta graveolens L.). The various extracts were analyzed by capillary chromatography, on an HP-5 (30 m) column, using nitrogen-phosphorus, flame ionization, and mass selective detection systems. Kováts indexes and mass spectra (electron impact, 70 eV) were employed for compound identification. The extracts from the various parts of rue studied had different compositions. The number of compounds detected at concentrations above 0.01% (w/w) in the extracts from leaves, flowers, stems and roots, was 78, 45, 25 and 24, respectively. 2-Nonanone (8.9%), 2-undecanone (13.4%), chalepensin (13.0%), and geijerene (19.3%) were the main constituents found in the extracts from rue leaves, flowers, stems and roots, respectively. Furanocoumarins, furoquinolines, hydrocarbons and benzodioxol derivatives were the main compound families found in all extracts, at total concentrations between 3.7 and 33.9%, depending on the part of the plant. The extraction method used has low environmental impact and produced solvent-free extracts in good yield with no pigments, waxes, resins, or high-molecular weight compounds which may interfere with the isolation and analysis of the alkaloids responsible for rue’s biological activity, which were extracted in relatively high yield.

Characterization of a commercial gas chromatography–flame ionization detection system for the in situ determination of C 5–C 10 hydrocarbons in ambient air

A commercial automated gas chromatograph with preconcentration on solid adsorbents (AirmoVoc HC1010) was coupled with a mass spectrometer in parallel with the flame ionization detection (FID) system and characterized for its suitability for quasi continuous measurements of atmospheric hydrocarbons (HCs) with a time resolution of 20 min. Of the 50 identified HCs in the range C 5–C 10, 15 elute in isolated peaks and 20 in groups of two or more HCs. The remaining 15 HCs suffer from coelution by oxygenated and halogenated compounds. Procedures to minimize and quantify the blanks and the memory from the adsorbents are described. Calibration was based on a custom-made diffusion source. The accuracy of this calibration (±10%, 2 σ) was verified by analysis of a certified 70-component standard (average deviation: −4.3±2%). During a field experiment in Summer 1998, the HC1010 system was compared with a custom-made GC system with cryogenic preconcentration and much better separation properties but lower time resolution. In ambient air, good agreement (2 σ deviation <14% or 10 ppt) was found for HCs and groups of HCs that are free from coelution with oxygenated compounds, whereas large discrepancies (in some cases more than a factor of three) were found for those HCs that coelute with oxygenated compounds, as identified by MS. Analysis of the mass spectra from those peaks via specific target ions showed much better agreement with the FID system of the reference GC within 25%.

Product studies of the OH‐ and ozone‐initiated oxidation of some monoterpenes

The OH‐ and O3‐initiated oxidation of five monoterpenes (myrcene, terpinolene, Δ3‐carene, α‐pinene, and β‐pinene) has been studied in environmental chambers equipped with either a Fourier transform infrared spectrometer or a gas chromatography/flame ionization detector system. The OH‐oxidation of myrcene and terpinolene is shown to lead to substantial yields of acetone (36 and 39%, respectively), while the acetone yield from the pinene compounds is quite small (4% and ∼2%, for α‐ and β‐pinene, respectively). Formaldehyde has been identified as a major product (yields of 20–40%) in the OH‐initiated oxidation of all five species. Formic acid was also observed in the OH‐initiated oxidation of all five monoterpenes, with yields of 2% from β‐pinene and 5–9% from the other species studied. The production of acetone from the reaction of monoterpenes with ozone in the presence of an OH scavenger was measured. The yields of acetone for the O3 reactions were α‐pinene, 0.03±0.01; β‐pinene, 0.009±0.009; Δ3‐carene, 0.10±0.015; myrcene, 0.25±0.06; and terpinolene, 0.50±0.06. The mechanism leading to the production of these compounds is discussed, as is the atmospheric relevance of the results. In particular, an estimate of the contribution of monoterpene oxidation to observed atmospheric levels of acetone and formic acid is made.

Automated capillary gas chromatographic system to monitor ethylene emitted from biological materials

An automated capillary gas chromatographic system to measure ethylene emitted from biological materials is presented. The system consists of an on-line sampling device, a thermodesorption preconcentration apparatus and a capillary gas chromatograph with a flame ionization detection system. The limit of detection achievable on the GC system alone is 5 pg ethylene. The use of the strong Carboxen 1000 adsorbent at a sampling temperature as low as −50°C allows sampling of volumes up to a few liters. Ethylene concentrations at low ppt levels can be accurately and reproducibly determined.

Analysis of methyl tert.-butyl ether and its degradation products by direct aqueous injection onto gas chromatography with mass spectrometry or flame ionization detection systems

A method was developed to analyze methyl tert.-butyl ether (MTBE) and its degradation products by gas chromatography with mass spectrometry (GC–MS) or flame ionization detection (FID) with direct aqueous injection. The column had dimensions of 30 m×0.25 mm with film thickness 0.25 μm and a stationary phase of FFAP (nitroterephthalic acid-modified polyethylene glycol). The optimized GC conditions for non-acid components were as follows: carrier gas flow-rate,1 mL/min; oven temperature, 35°C for 5.5 min, ramped to 90°C at 25°C/min, then ramped to 200°C at 40°C/min and held at 200°C for 8 min. The conditions for the acid components were: carrier gas flow-rate, 1 mL/min; oven temperature, 110°C for 2 min, ramped to 150°C at 10°C/min, then ramped to 200°C at 40°C/min. The injection port contained a silanized-glass reverse-cup liner filled with Carbofrit. The minimum concentrations for the linear range for the selective ion monitoring mode were 30 to 100 μg/L, depending on the analytes. The minimum detection limit was 1 mg/L for MTBE and tert.-butanol when using FID. More components could be analyzed with the FFAP-type column than with the cyanopropylphenyl–dimethyl polysiloxane-type column.

In situ measurements of C2‐C10 volatile organic compounds above a Sierra Nevada ponderosa pine plantation

A fully automated gas chromatograph‐flame ionization detector system was designed and built to measure ambient concentrations of C2‐C10 volatile organic compounds, including many oxygenated compounds, without using liquid cryogen. It was deployed at Blodgett Forest Research Station in Georgetown, California, 38°53′42.9″N, 120°37′57.9″W, 1315 m elevation. More than 900 in situ measurements were made above a ponderosa pine canopy at 40‐min intervals, continuously from July 2 through August 1, 1997. Factor analysis and observed temporal patterns were used to categorize sources for measured compounds as biogenic or anthropogenic or both. Compounds that were clearly biogenic included methylbutenol, isoprene and its oxidation products (methacrolein and methyl vinyl ketone), and terpenes (α‐pinene, 3‐carene, d‐limonene). Other compounds were partially biogenic, including acetone, ethene, propene, hexanal, acetaldehyde, and methanol. Hydroxyl radical (OH) loss rates were dominated by the clearly biogenic compounds, accounting for 70% of the loss under mean midday conditions. The most important single compounds were isoprene (33%) and methylbutenol (21%). These two compounds were dominant under all conditions, including the coldest and most polluted days. Under the most polluted conditions, acetaldehyde became very important, accounting for 13% of the total. Total OH loss rates were highly correlated with temperature because emissions of biogenic compounds, which dominate OH loss, are strongly temperature dependent. Much of the research on biogenic volatile organic compounds has focused on isoprene and terpenes. Our results suggest that quantifying and understanding factors controlling biogenic emissions of other compounds such as methylbutenol, acetone, hexanal, methanol, and acetaldehyde are critical for improving our understanding of regional photochemistry.

Suitability of Thin-Layer Chromatography-Flame Ionization Detection with Regard to Quantitative Characterization of Different Fossil Fuel Products. II. Calibration Methods Concerning Quantitative Hydrocarbon-Group Type Analysis

Time-consuming external standard-based calibration methods are usually performed for hydrocarbon group type analysis (HGTA) of fossil fuels, regardless of the instrumental chromatographic technique. In this work, HGTA of a broad variety of coal and petroleum products is performed using a modern thin-layer chromatography-flame ionization detection (TLC-FID) system and a rapid method based on internal normalization. Repeatability, linear intervals, and sample load ranges for quantitative application of this method are detailed for different products that cover a broad range of boiling points and chemical functionalities in the field of fossil fuels: a heavy oil and its derived hydrocracked products, raw and chemically-modified petroleum asphaltenes, a coal-tar pitch, several coal extracts, and coal hydroliquefaction products. Results from external standard calibration and a normalization method (both obtained by TLC-FID) are in agreement, and they are validated using TLC-ultraviolet scanning. The use of the latter demonstrates that TLC-FID can also be applied to products such as coal extracts and hydroliquefaction products, despite these products being more volatile than petroleum asphaltenes or heavy oils. For preparative purposes when external calibration is necessary, preparative TLC and SPE are less time-consuming alternatives to MPLC fractionation, providing similar results.

Internal Lipid Wool Structure Modification Due to a Nonionic Auxiliary Used in Dyeing at Low Temperatures

An analytical and microscopical study of wool fibers differently treated with a non-ionic dye auxiliary product such as Baylan NT elucidates the action mechanism of this compound in low temperature dyeing of wool. Lipids are extracted from wool samples previously treated with Baylan NT, and the compounds are analyzed quantitatively with thin layer chromatography coupled to a flame ionization detection system. Previous solubilization of free fatty acids by the Baylan treatment is considered to be the main cause of some changes in the lipid morphological structure, resulting in the release of ceramides in subsequent solvent extraction. These are found in a significantly higher amount in the extract of the wool treated with the auxiliary compound. Furthermore, the microscopical study shows higher penetration of the fluorescent dye in wool fibers treated with the auxiliary compound, thereby confirming the importance of cell membrane complex modification in the improving the dyeing characteristics of wool and permitting dyeing at low temperatures.

Measurement of methane and carbon dioxide fluxes from peatland ecosystems by the conditional-sampling technique

The conditional sampling method was used to measure methane (CH4) and carbon dioxide (CO2) fluxes from peatlands in northern Scotland. Preliminary data were obtained using a simple system. Subsequent automation made continuous flux-measurements possible. Observed CH4 fluxes were in the range −70 to +110 μmol m−2 h−1 with a mean flux of 23 μmol m−2 h−1. Peak photosynthetic CO2 fluxes were in the range −10 to −30 mmol m−2 h−1. Nocturnal respiration ranged from 0 to +10 mmol m−2 h−1. The conditional sampling observations showed reasonable agreement with measurements of flux by eddy-covariance, gradient and aircraft methods. Error analyses and laboratory tests were conducted to determine the precision of the flux-measurement system. The dominant error was associated with the determination of the mixing-ratio difference in conditionally-sampled updraught and downdraught air. The standard error of the difference for CH4 was typically 0.15 ng g−1 (0.3 parts in 109 (p.p.b.)) using a careful high-repetition sampling strategy with a modified gas chromatographic/flame ionization detector system. Under typical daytime atmospheric conditions this corresponded to a standard error in the flux measurement of 10 μmol m−2 h−1, which is consistent with field observations. The empirical beta factor in the conditional sampling equation was found to be insensitive to changes in turbulence intensity and atmospheric stability. Simple upscaling models were used to estimate annual carbon-fluxes to Great Britain's peatlands of −0.5 Mt of carbon in the form of CO2 and 18 kt in the form of methane.

Measurement of methane and carbon dioxide fluxes from peatland ecosystems by the conditional‐sampling technique

AbstractThe conditional sampling method was used to measure methane (CH4) and carbon dioxide (CO2) fluxes from peatlands in northern Scotland. Preliminary data were obtained using a simple system. Subsequent automation made continuous flux‐measurements possible. Observed CH4 fluxes were in the range −70 to +110 μmol m−2 h−1 with a mean flux of 23 μmol m−2 h−1. Peak photosynthetic CO2 fluxes were in the range −10 to −30 mmol m−2 h−1. Nocturnal respiration ranged from 0 to +10 mmol m−2 h−1. The conditional sampling observations showed reasonable agreement with measurements of flux by eddy‐covariance, gradient and aircraft methods. Error analyses and laboratory tests were conducted to determine the precision of the flux‐measurement system. The dominant error was associated with the determination of the mixing‐ratio difference in conditionally‐sampled updraught and downdraught air. The standard error of the difference for CH4 was typically 0.15 ng g−1 (0.3 parts in 109 (p.p.b.)) using a careful high‐repetition sampling strategy with a modified gas chromatographic/flame ionization detector system. Under typical daytime atmospheric conditions this corresponded to a standard error in the flux measurement of 10 μmol m−2 h−1, which is consistent with field observations. The empirical beta factor in the conditional sampling equation was found to be insensitive to changes in turbulence intensity and atmospheric stability. Simple upscaling models were used to estimate annual carbon‐fluxes to Great Britain's peatlands of −0.5 Mt of carbon in the form of CO2 and 18 kt in the form of methane.

Particulate lipid class composition of three marine phytoplankters Chaetoceros gracilis, Isochrysis galbana (Tahiti) and Dunaliella tertiolecta grown in batch culture

The green algae D. tertiolecta, the flagellate I. galbana and the diatom C. gracilis were grown in batch cultures. The organisms were analysed for lipid class composition at the logarithmic and stationary growth phases using the Chromarod-Iatroscan thin layer chromatography with flame ionization detection (TLC-FID) system. There were major differences in lipid class production among the organisms investigated, but few differences in lipid class distribution between log phase and stationary phase cultures of D. tertiolecta and I. galbana. C. gracilis displayed the general trend exhibited in diatom metabolism, which can be characterized by an increase in triacylglycerol synthesis in situations of stress.

Fully automated gas chromatograph-flame ionization detector system for the in situ determination of atmospheric nonmethane hydrocarbons at low parts per trillion concentration

A completely automated gas chromatography-flame ionization detector system with cryogenic sample freeze-out for measuring atmospheric non-methane hydrocarbons was deployed at the Mauna Loa Observatory, Hawaii during the MLOPEX II experiment, September 1991 through August 1992. The system was designed to (1) rapidly trap air samples of up to 4 litres volume to allow for sub-parts per trillion detection limits, (2) eliminate interferences from ambient ozone, water vapor carbon dioxide, (3) reduce to negligible levels any contamination in the analytical systems, and (4) allow for continuous, unattended operation. The instrumentation consisted of two parallel analytical systems, employing packed capillary chromatographic columns, which allowed quantification of C 2–C 10, non-methane hydrocarbons from sub-parts per trillion to parts per million concentrations. A dynamic dilution system was used to calibrate the analytical system over the range of concentrations measured (low parts per trillion to parts per billion) at this site.

The PRIME Lab gas ionization detector

A gas ionization detection system was built for optimal identification of AMS radionuclides, in particular 10Be and 36Cl. For 36Cl, a combination of 1) the difference in arrival times for electrons at two anode plates and 2) a novel split anode plate has led to a reduction in misidentified 36S. A peak-stabilizing routine incorporated in the data acquisition system has allowed us to run at higher counting rates. Changing to propane gas has reduced random signal amplitude shifts.

Evaluation of susceptibility to oxidation of linoleyl derivatives by thin-layer chromatography with flame ionization detection

A simple and rapid method for the evaluation of susceptibility to oxidation in microsamples was developed using a thin-layer chromatographic-flame ionization detection (TLC-FID) system. The procedure was applied to linoleic acid, methyl linoleate, trilinolein and sucrose octalinoleate. Samples of 15 μg were spotted on Chromarods, subjected to different temperatures for various times and analysed by TLC-FID. Oxidized products from linoleyl derivatives were determined from the amounts of unoxidized samples, determined in turn by two approaches, i.e., using calibration graphs or adding squalane an an internal standard.