Flame Ionization Detection System Research Articles

Identification of three novel compounds in wine by means of a laboratory-constructed multidimensional gas chromatographic system

A laboratory-made off-line multidimensional GC–GC system has been optimized and applied to the isolation and identification of three novel aroma compounds in wine. The system comprises two independent chromatographs equipped with four-port manually actuated valves and fast capillary connectors that make it possible to quickly transfer a capillary trapping loop from the first to the second system. The first system includes a split/splitless injector, a thick phase semi-capillary column, the valve and both a flame ionization detection (FID) system and a sniffing port. The trapping loop lies outside the chromatograph and it is immersed in a Dewar with liquid nitrogen. The second system includes a programmable temperature vaporization (PTV) injector, the valve, the analytical column and two parallel detectors (a MS system and a sniffing port). The injection of large sample volumes (90 μl) in the first GC system and the general operation of the system have been optimized. The extract was obtained by purging the wine at 37 °C with a stream of nitrogen and trapping the volatiles in a bed containing 1 g LiChrolut EN. Fatty acids and alcohols were removed by washing the resins with a water/methanol solution containing 1% NaHCO 3, and volatiles were recovered with dichloromethane. The GC–MS analysis of the cuts obtained in the first GC system made it possible to identify by first time in wine the strong smelling compounds ethyl 2-, 3- and 4-methylpentanoate.

Determination of the carbon deficiency in the flame ionization detector response of long-chain fatty acid methyl esters and dicarboxylic acid dimethyl esters

Carbon deficiencies (CDs) of long-chain fatty acid methyl esters (FAMEs) and dicarboxylic acid dimethyl esters (DDMEs), which lead to decreased response in a flame ionization detection (FID) system, were determined by using full responding hydrocarbons (heptadecane, eicosane and alpha-cholestane) as references. For saturated FAMEs ranging from C 12 to C 22 and for DDMEs ranging from C 4 to C 10, CDs between 1.3 ± 0.12 and 1.7 ± 0.36 per ester group were recorded. All values were significantly ( P < 0.05) greater than 1. Generally, response factors for gas-chromatographic analysis using FID have been calculated on the theory that the CD of FAMEs is 1 per ester group. However, this theory could not be confirmed experimentally for short-chain FAMEs of less than 8 carbons as CDs of around 1.5 were reported for C 4 and C 6 FAMEs. The study presented here contributes an approach to this problem by confirming the validity of response factors calculated from a CD of 1.5 per ester group as well as for long-chain FAMEs and DDMEs.

The role of volatile organic compounds in the polluted urban atmosphere of Bristol, England

Abstract. The results of a field campaign carried out from early spring through to the late summer of 2000, in Bristol, England, are presented. Continuous measurements of over 40 hydrocarbons have been made at an urban background site, located at Bristol University, for approximately nine months using a Gas Chromatography - Flame Ionisation Detection (GC-FID) system and for a selection of halocarbons for approximately one month using a Gas Chromatography - Electron Capture Detection (GC-ECD) system. In this paper we present the time-series of the nine halocarbons and selected hydrocarbons. Daytime and night-time hydroxyl radical concentrations have been estimated based on the diurnal variations of a selection of the measured hydrocarbons. The average summer daytime concentration of OH was found to be 2.5x106 molecules cm-3 and the night-time concentration to be in the range 104 to 105 molecules cm-3. In addition, the role played by certain VOCs in the formation of ozone is assessed using the POCP (Photochemical Ozone Creation Potential) concept.

Thermal decomposition of surface compounds for the generation of small quantities of acetaldehyde: Calibration of a thermal desorption–gas chromatography–flame ionization detection

The paper presents a new method for the generation of acetaldehyde in the amounts that allow to calibrate the measuring system. The method is based on thermal decomposition of surface compounds at the range 130–190 °C, in which an acetaldehyde as the decomposition product is released. The synthetic pathway leading to the desired surface compounds is described. Investigations demonstrated that the synthesis of the compounds on the surface of the support material (silica gel) was carried out homogeneously. The technique proposed was used for the generation of gaseous standard mixtures containing acetaldehyde for the calibration of a thermal desorber–gas chromatograph–flame ionization detector system.

Effect of the carbon dioxide modifier on the lipid composition of wool wax extracted from raw wool

Wool wax or lanolin is a unique substance secreted by sheep and forms a natural protective coating on wool fibres. It is widely used in pharmaceutical and cosmetic formulations. However, different systems of wool wax recovery from scouring liquour provide a dark impurified greasy product. This product has a lipid composition that differs from the wool wax present on wool fibres. The wool wax extraction method from raw wool with pressurised CO 2 and different modifiers at constant pressure and temperature was studied. Thin-layer chromatography coupled to an automated flame ionisation detection system (TLC/FID) was used to analyse the different lipid classes present in the collected extracts. Moreover, a detailed structural comparison of the cholesteryl esters and hydroxycholesteryl esters was carried out by means of sub-ambient pressure chromatography mass spectrometry in the electron impact and in the ammonia positive chemical ionisation modes. For comparison, qualitative and quantitative analyses of the lanolin extracted in Soxhlet with dichloromethane and commercial cosmetic lanolin were carried out. Differences in the quantity of wool wax extraction and in the lipid composition of different wool wax extracts were detected by changing the modifier polarity.

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.

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.

Flame ionization detection after splitting the water effluent in subcritical water chromatography

The coupling of subcritical water separation with flame ionization detection (FID) in the split mode has been investigated in this study. In order to keep the FID system stable during subcritical water separation, a Tee union was connected between the separation column and the FID system to split the water flow. The ratio of the water flow to the FID system over the flow-rate to a waste bottle varied depending on the dimension of capillary tubings and the total water flow-rate used. Separations of several carbohydrates, carboxylic acids, and amino acids were performed on commercially available columns using a laboratory-made subcritical water chromatography–FID system. The FID system was very stable in this split mode even at total flow-rate as high as 1.24 ml/min. The linear dynamic range was up to three orders of magnitude and the limit of detection (LOD) ranged from 38 to 111 ng (306–925 ng/μl injected) with split ratios of ∼1:10 to ∼1:17 (FID/waste bottle) for several analytes studied. However, the LOD can be significantly lowered by adjusting the dimensions of the restrictors to allow a higher percentage of the total flow to the FID system.

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%.

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.

Hydrocarbon source apportionment in Mexico City using the chemical mass balance receptor model

A field study was conducted in Mexico City during May–November 1997 to determine non-methane hydrocarbons (NMHC) species emitted from different sources: application of slow curing asphalt pavement, liquefied petroleum gas (vapour phase), dry cleaning, graphic arts, landfill, emissions of motor vehicle exhaust inside a tunnel, hot soak, whole gasoline, painting operations and degreasing. Forty-five ambient air samples of NMHC were simultaneously collected from 6:00 to 9:00 a.m. at three different sites, Xalostoc, Pedregal and La Merced, denominated receptors, during the spring and fall of 1996. In both cases samples were collected in stainless-steel canisters and analysed by gas chromatography with flame ionisation detection system. Based on these measurements the chemical mass receptor model (CMB) was applied to estimate the contribution of the different NMHC source to ambient pollution. The average results for the two sampling periods showed that the major sources of NMHC for the three sites were: motor vehicle exhaust with an average contribution of 54.9, 57.4 and 63.8% for Xalostoc, Pedregal and La Merced, respectively, followed by handling and distribution of liquefied petroleum gas with 28.5% in Xalostoc, 20.0% in Pedregal and 24.0% in La Merced.

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.

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.

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.

Chromium determination by supercritical fluid chromatography with inductively coupled plasma mass spectrometric and flame ionization detection

Supercritical fluid chromatography (SFC) has been investigated for the separation of a pair of β-ketonate chromium compounds and a thermally labile organochromium dimer. A limited comparison between flame ionization detection (FID) and inductively coupled plasma mass spectrometric (ICP-MS) detection of these compounds is presented. The β-ketonate complexes were observed with both detectors, while the thermally labile dimer was not observed with ICP-MS detection. Detection limits for these compounds with ICP-MS were in the range of 0.9 to 3 pg with FID giving values between 10 and 250 pg. Reproducibility of the method is between 1 and 4% relative standard deviation (R.S.D.). The technique provided a linear response over approximately three orders of magnitude. The effect of two mobile phases (nitrous oxide and carbon dioxide) on the detection by each of the detectors are presented in a qualitative manner. Finally, the SFC-ICP interface heating method and the manner in which the restrictor is heated in the FID system are compared and there effect on the chromatography discussed.

Sensory Gas Chromatography for Evaluation of Taste and Odor Events in Drinking Water

A sensory gas chromatography (sensory GC) procedure with appropriate quality assurance steps was developed to evaluate ng/l concentrations of odorous chemicals in drinking water. Closed loop stripping analysis was used to concentrate the chemicals in the water samples. Sensory GC analysis was completed by smelling the effluent at the exit port of an on-column injector capillary GC system. An identical and parallel GC flame ionization detector system was used to monitor the sensory gas chromatograms. The sensory GC analysis is important because it can detect some of the individual components of the odor that a sensory panel determines on a water sample. The relationship between sensory panel response and the sensory GC procedure were investigated near threshold odor concentration levels and the data shows that sensory GC does not always correlate with sensory panel evaluations. This can be caused by the concentrations differences of the chemicals in the mixture and synergistic and antagonistic effects. Two taste and odor events reported at the Baxter Water Treatment Plant of the city of Philadelphia on the Delaware river were investigated. The events were first a metallic aftertaste accompanied by a burnt rubber odor and second a cucumber odor in the drinking water. The cases studied illustrate the use of FPA, sensory GC and GC/MS to understand the chemical nature of the odors present in the samples.

Development of Analytical Methodology and a Report on Collaborative Study on the Determination of Morpholine, Cyclohexylamine, and Diethylaminoethanol in Aqueous Samples by Direct Aqueous Injection Gas Chromatography

A direct aqueous injection gas chromatographic procedure for the determination of morpholine, cyclohexylamine, and diethylaminoethanol has been developed. The method employs graphitized carbon B (60 to 80 mesh) coated with 4.8% polyethylene glycol 20 M + 0.4% potassium hydroxide and a flame ionization detection system. The detection limits (3 × signal-to-noise ratio) for morpholine, cyclohexylamine, and diethylaminoethanol were 55 ng, 52 ng, and 53 ng, respectively. Five spiked samples containing the three amines in concentrations ranging from 0.5 to 3.0 mg/mL after appropriate dilution have been analyzed by six laboratories. A duplicate of one concentration level has been separately spiked with 50 ppm of iron salts to study the influence of iron salts on the analytical technique. Statistical treatment complementary to that outlined in ASTM D 2777-86 was applied. Significant biases were observed at some spike levels for morpholine and cyclohexylamine; bias changes were not consistent with increasing concentration. No significant biases were noted for diethylaminoethanol. There was no evidence of interlaboratory variations for any concentrations of morpholine. Significant interlaboratory variability was observed for some concentrations of cyclohexylamine and diethylaminoethanol. Further, the presence of iron salts shows negligible influence on the analytical technique for the three amines.

A Simplified Procedure for the Isolation, Characterization, and Identification of Weak Acid and Neutral Drugs from Whole Blood

The presented method utilizes commercially available Chem Elut columns for the extraction of weak acid and neutral drugs. The residue from this extraction is purified by partitioning between hexane and acetonitrile. The drugs are analyzed using a gas chromatograph equipped with a 0.53-mm i.d. dimethyl silicone capillary column, a packed column inlet adapter, and a flame ionization detector. The drugs are characterized by their retention index. The procedure is rapid, and clean chromatograms are the rule with essentially no lipid interference for flame ionization or mass spectrometer detection systems. The retention index has proven to be a very reliable parameter for describing chromatographic behavior. For probarbital, the internal standard, the calculated retention index averaged 1529.70 with a standard deviation of 1.27 index units (n = 115).