Flame Ionization Detector Response Research Articles

TLC–FID (Iatroscan) analysis of heavy oil and tar sand samples

TLC–FID (Iatroscan) reproducibility of the fractionation [saturated hydrocarbons, aromatic hydrocarbons, resins, asphaltenes (SARA)] of heavy oil and tar sands samples has been optimized by avoiding overloading and channeling caused by very small sample spot sizes at the origin of the silica - coated rods (S-III). Doping the rods with copper (II) sulfate increased the signal response for the saturate and aromatic fractions and resulted in a decrease in the relative standard deviation of the measured peak areas for all four SARA fractions. Comparison of precipitated asphaltenes and column chromatographic separation of the maltene fraction with Iatroscan data is problematic because resins are typically occluded in the precipitated asphaltenes and polar fractions appear to have variable flame ionization detector (FID) response factors.

Effects of Spark Ignition Timing and Fuel Injection Strategy for Combustion Stability on HEV Powertrain during Engine Restart and Deceleration Driving

Stringent regulations of exhaust emission and fuel economy from vehicles have become major issues in the automotive industry. Hybrid Electric Vehicle (HEV) can be one of the crucial alternative plans over current conventional vehicle, but they have drawbacks such as the increase of engine out total hydrocarbon (THC) emission and the deterioration of combustion stability at frequent engine stop and restart. This study performs experimental investigation to obtain a better understanding of THC emission characteristic at engine restart and deceleration driving on a HEV powertrain of parallel motor/generator type using a Fast response Flame Ionization Detector (FFID) and specified tool for cycle by cycle, cylinder to cylinder combustion and engine control characteristic analysis during transient state of HEV powertrain. The experimental conditions cover variation of high voltage battery State of Charge (SoC), spark ignition timing and injected fuel mass. As an experimental result, the effect of the spark timing control is so little, but the reasonable injection duration for stable combustion is more than 7 (ms) at the first cycle shortly after engine start-up by motor although the injection rate is 2.7 ~ 3 (ms) at idle state. The reason why more fuel was injected was that the deposited fuel in the cylinder and intake port was reduced due to discharging and vaporization during deceleration step before idle stop.

Comparative Study of the Separation and Quantification of Lipid Classes Separated on Chromarods‐A and Chromarods‐SIII by Thin Layer Chromatography with Iatroscan (Mark‐III) Flame Ionization Detection (TLC‐FID)

Thin layer chromatography (TLC) on Chromarods‐A and –SIII were used for the separation of common lipid classes which were detected and quantified using Iatrosan Mark‐III with Flame Ionization Detection (FID). Two different lots from each type of Chromarods were used and half of each lot (5 rods) was considered as 1 analytical unit. Variability of the FID response for 11 different lipid classes (neutral and polar) among rods of each lot, among different analytical units as well as the variability between 2 different lots of the same type of Chromarods were compared statistically. Variability of the response for these lipid classes by an individual rod during repeated analysis was also investigated. Calibration curves of the FID response vs. sample loads were used to develop corresponding calibration models that can be used for quantification of lipid classes separated on these Chromarods. There was no significant difference (p>0.05) in the FID response for all lipid classes separated on Chromarods‐A or ‐SIII. However, the FID responses for all lipid classes separated on Chromarods‐A were significantly different from those on Chromarods‐SIII (p<0.01). There was no significant difference in the FID response among analytical units of the same type of Chromarods. Curvilinear relationship of the FID response against the sample load was common to all lipid classes for both Chromarods‐A and –SIII. Several calibration equations were derived and Power Law models (y=axb) appear to be the most convenient and appropriate for rapid quantitative analysis of lipid classes although an addition of a quadratic and/or cubic term further improved the statistical validity of the model.

Effect of Hydrogen/Air Flow Rates and Scan Rate on the Flame Ionization Detection Response of Phospholipids, and their Qualitative and Quantitative Analysis by Iatroscan (Mark‐6s) TLC‐FID

The combined effect of scan speed, hydrogen and air flow rates on the flame ionization detection (FID) peak response of phospholipid classes has been studied to determine the optimum levels of these parameters. The phospholipid composition of different types of commercial lecithins, as well as lecithins combined with fish oils, has been analyzed by Iatroscan TLC‐FID Mark‐6s under optimized conditions. An air flow rate of 2 L/min, a hydrogen flow rate of 150–160 mL/min, and a scan speed of 30 s/rod seem to be the ideal conditions for scanning phospholipids with complete pyrolysis in the flame in the Mark‐6 model. Increasing the scan speed rapidly decreased the FID response. A hydrogen flow rate as high as 170 mL/min could be used at relatively low air flow rates (<2 L/min) and the response declined when both air flow rate and hydrogen flow rate increased simultaneously. Both linear and curvilinear relationships had highly significant correlations (p<0.01) with the sample load. Time course reactions, including the hydrolysis of phosphatidylserine using enzymes, can be successfully monitored by the Iatroscan TLC‐FID Chromarod system.

Factors Affecting Linearity and Response of Flame Ionization Detector

The application of gas chromatography to the analysis of both major and minor compounds in a sample requires a detector of high sensitivity and wide response range, such as a flame ionization detector. Response, linearity, and noise of the flame ionization detector are discussed and the effect of parameters, e.g., flow rates of the carrier, fuel gases, and sample capacity on the response of the detector are investigated. Also, it is necessary to know whether its response is strictly linear over the required range. This research aims to study the response characteristics of flame ionization detectors and their linear range. The optimum operating conditions have also been investigated in some detail.

A Novel Miniaturized Flame Ionization Detector for Portable Gas Chromatography

A novel miniaturized flame ionization detector (FID) operated by battery, which can be used as a detector in portable gas chromatography (GC) is devised and manufactured. It is characterized by the structure of building blocks, small volume, low energy consumption, and needing only two gases, which can be used for detection of hydrocarbons in portable GC. The miniaturized detector mainly includes a porous metallic diffuser plate, bugle-figuration collector, quartz capillary flame tip, and self-heated system. The miniaturized FID is easy to fabricate and assemble because of its structure of building blocks. The FID response is linear over six orders of magnitude and the detection limit of 0.518 ng for benzene, 0.430 ng for n-dodecane, 0.473 ng for naphthalene, and 0.509 ng for n-tetradecane.

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.

Effects of experimental conditions on the determination of the effective carbon number

The response of the flame ionization detector (FID) is proportional to the carbon number of hydrocarbon molecules; however, heteroatoms attached to the carbon chain can decrease the detector's response. Sternberg was the first who determined the effective carbon number increments (ECN inc), which show how different atoms contribute to the response of a molecule as a whole. If the extent of the contributions of different atoms or functional groups to the FID response of a molecule is known, one could calculate the relative response of analytes not available as a pure, authentic standards. An accurate and reliable quantitative analysis requires an accurate determination ofECN inc. The effects and parameters influencing theECN inc value have to be examined. Stemberg determined the effects of the detector geometry and of the parameters to the response. However, we assume that other experimental conditions can indirectly also affect theECN contributions. In this study, the effects of the temperature of the injector, detector and column and of the injection modes were investigated. We compared theECN values obtained at different concentrations and measured them with different hydrocarbons as the intermal standards.

Measurements of biogenic VOC emissions: sampling, analysis and calibration

We describe an experimental system and techniques for sampling and analyzing biogenic emissions of volatile organic compounds (VOC). The system uses a Teflon chamber to enclose a single branch of a tree. Temperature, photosynthetic active radiation (PAR), relative humidity and carbon dioxide concentration are continuously monitored with a time resolution of five minutes. VOCs are sampled on tubes containing solid adsorbents (Tenax TA and Carbotrap) with a time resolution of 1 h. Composition and concentration of VOC emissions are measured with a gas chromatographic system equipped with a flame ionization detector (FID) for quantitative and a mass spectrometer (MS) for qualitative analysis. To calibrate the system, a diffusion source was built to produce standard mixtures of up to 36 different compounds with mixing ratios at low concentrations and high accuracy. The diffusion rates were monitored over 17 months and showed variations between 0.2 and 7.6% for monoterpenes (expect for α-phellandrene, α-terpinene and γ-terpinene) and between 10.6 and 22.6% for sesquiterpenes. FID response factors calculated from calibration measurements were corrected using correction factors based on the effective carbon number concept. The individual response factors of 23 compounds were combined to a mean response factor (RF m) with a value of 23,100 μV s ng −1 and a standard deviation of 9%. The system described here was used to measure VOC emission rates of Scots pine ( Pinus sylvestris) in 1998 and 1999.

Measurements of cycle resolved air-fuel ratio near the spark plug in a spark ignition engine

Mixture preparation is a key contributor to both the combustion and emissions of the automotive gasoline engine. The air-fuel ratio near the spark plug may have an effect on combustion characteristics, especially at low load, since it is related to flame development. Therefore, measurements of the cycle-resolved equivalence ratio near the spark plug are particularly important for a better understanding of their contribution to combustion and emissions. This paper describes how the in-cylinder equivalence ratio was determined from the measured hydrocarbon concentrations near the spark plug using a fast response flame ionization detector (FRFID). The procedures established were then applied to a limited range of engine operating conditions, and the cycle-resolved equivalence ratio near the spark plug was determined from the measured hydrocarbon concentration. The results showed that with premixed propane fuel the cyclic variation in equivalence ratio near the spark plug was quite small and corresponded to the overall equivalence ratio from the universal exhaust gas oxygen (UEGO) sensor signal. However, with gasoline fuel the equivalence ratio near the spark plug varied by up to 10 per cent and did not coincide with the UEGO sensor signal on a cyclic basis. The variation in equivalence ratio near the spark plug affected the heat release rate, which in turn affected the indicated mean effective pressure (i.m.e.p.). The equivalence ratio excursions and its effects during acceleration and deceleration are strongly related to the exhaust emissions, fuel economy and so on. With this in mind, the quantitative measurement method using the measured hydrocarbon concentrations was studied for detailed analysis during transient conditions. It was also observed that cyclic variation in the equivalence ratio near the spark plug might be one cause of cycle-by-cycle variation.

Quantitative analysis of triterpenes friedelan-3-?-ol and friedelin in Maytenus aquifolium by high-resolution gas chromatography and high- temperature capillary gas chromatography

The quantitative analysis of the pentacyclic triterpenes friedelan-3-β-ol and friedelin by high-temperature capillary gas chromatography (HT-CGC) and high-resolution gas chromatography (HRGC) is described. These compounds are markers of Maytenus aquifolium and M. ilicifolium (Celastraceae), plants which show anti-ulcer activity and which are used medicinally in Brazil under the name “espinheira santa”. HT-CGC was more efficient than conventional HRGC for the quantitative evaluation of triterpenes in the hexane extracts of leaves of M. aquifolium owing to the reduced retention times attainable without loss of resolution. The flame ionisation detector response and detection limits for both triterpenes using HRGC and HT-CGC were also established. Copyright © 2000 John Wiley & Sons, Ltd.

Flame‐ionization detector response to methyl, ethyl, propyl, and butyl esters of fatty acids

AbstractThe concept of theoretical response factors is not directly applicable to methyl esters of short‐chain fatty acids (FA), since their carbon deficiency is larger than expected from theory. Substituting the methyl group by an ethyl, propyl, or butyl group improved the flame‐ionization efficiency of fatty acid esters gradually, up to the point where the empirical response factors of the butyl esters were identical within experimental error to the theoretical values. Butyl esters of FA have a uniform flame‐ionization detection (FID) response irrespective of the number of carbon atoms contained in the FA. They exhibit a carbon deficiency of 1.0, i.e. the carbonyl carbon atom does not respond, as expected from theory. Compared to methyl esters, which have a carbon deficiency of 1.4–1.5 for short‐chain FA, use of butyl esters has the advantage that a precalculation of the FID response enables the analyst to judge whether the analytical system employed works properly and the data produced are accurate and reliable. Both acid (BF3 or H2SO4)‐and alkali (butoxide)‐catalyzed butyl ester preparation were equally effective, giving the analyst a choice of methods so that different analytical needs can be addressed efficiently. Computing response factors and comparing the theoretically expected values with those obtained experimentally gives the experimenter an indication whether the analytical system employed for FA profiling (transesterification plus the subsequent gasliquid chromatographic separation and quantitation by FID) works properly. This setup is particularly useful for an accurate analysis of the FA profile of milk fat.

Simultaneous Determination by Capillary Gas Chromatography of Organic Acids, Sugars, and Sugar Alcohols in Plant Tissue Extracts as Their Trimethylsilyl Derivatives

A capillary gas chromatographic (GC) method for the simultaneous determination of organic acids, sugars, and sugar alcohols extracted from plant tissues is described. Plant leaves were extracted in 5% (w/v) perchloric acid and neutralized extracts were purified using C18cartridges. Organic acids, sugars, and sugar alcohols in purified extracts were converted to their trimethylsilyl (TMS)/TMS-oxime derivatives prior to separation and detection by capillary GC with flame ionization detection (FID). Derivatization procedures were investigated in detail and the compounds of interest were readily converted to their TMS/TMS-oxime derivatives using hexamethyldisiazane reagent in acetonitrile solvent (1:6 v/v) at 100°C for 60 min. The derivatives were sufficiently volatile and stable. The FID response to derivatized compounds was generally linear in the concentration range 30–300 μg ml−1, with detection limits in the order of 3–76 ng. The proposed method was demonstrated for the determination of organic acids, sugars, and sugar alcohols in leaf extracts of two native Australian plants.

Prediction of flame ionization detector response factors using an artificial neural network

An artificial neural network (ANN) was successfully developed for the modeling of flame ionization detector response factors. The generated ANN was evaluated and applied for the prediction of response factors of several varieties of organic compounds. The results obtained using neural network were compared with different sets of experimental values as well as with those obtained using multiple linear regression technique. Comparison of neural network standard error of prediction values with those obtained using regression equations shows the superiority of ANNs over that of regression models. Calculations of Dietz response factor for two different prediction sets show that an ANN has a good predictive power.

Scaling of Infrared Remote Sensor Hydrocarbon Measurements for Motor Vehicle Emission Inventory Calculations

Infrared (IR) remote sensors calibrated with propane understate volatile organic compound (VOC) concentrations in vehicle exhaust by 30−70% when compared to flame ionization detectors (FID). The difference depends on VOC composition and arises because many organic compounds in vehicle exhaust absorb less IR radiation than propane on a per-carbon basis. This study demonstrates an approach for scaling infrared measurements to reflect more accurately total exhaust VOC emissions from on-road motor vehicle fleets. Infrared versus flame ionization detector response to individual VOC was measured in the laboratory for methyl tert-butyl ether and a range of alkanes, alkenes, and aromatics that are prominent in vehicle exhaust. Overall IR/FID response to real exhaust mixtures was calculated by summing the response contributions of all individual VOC constituents. Average IR/FID response factors were calculated for typical on-road vehicle fleets based on VOC speciation profiles measured in several U.S. roadway tunnels. Results indicate that hydrocarbon concentrations measured by remote sensors with 3.4 μm filters should be multiplied by a factor of 2.0 ± 0.1 for light-duty vehicles using either California or federal reformulated gasoline blends and by 2.2 ± 0.1 when conventional gasoline is used.

Identification limits for volatile organic compounds in the blood by purge-and-trap GC-FTIR.

An analysis method for volatile organic compounds in blood based on purge-and-trap extraction coupled with gas chromatography-Fourier transform infrared spectroscopy (GC-FTIR) was developed. The sample volume was 5 mL, and the internal standard was diethyl ketone. The chromatographic separation was carried out on a PoraPLOT Q capillary column, and the effluent was first directed to the FTIR and then to a flame ionization detector (FID). FTIR identification limits were measured for 27 volatile organic compounds; the criteria for the limit were that the first hit-list position should be obtained against the Sadtler library, which contains 3240 spectra, and that the correlation value should exceed 0.5. It was required that the peak be seen by FID but not necessarily by a Gram-Schmidt chromatogram. The FTIR identification limits, ranging from 0.01 mg/L for ethyl acetate, methylethyl ketone, and sevoflurane to 24 mg/L for methanol, generally allowed the detection of volatile-substance exposure at a lower level than is acutely toxic. Quantitative calibration data were presented for selected substances, based on the FID response, which shows that the method is also amenable to quantitative analysis. The throughput of the method without additional automation is five samples per day, the purge-and-trap stage being the limiting factor.

Estimation of Flame-Ionization Detector Relative Response Factors for Oligomers of Alkyl and Aryl Ether Polyethoxylates using the Effective Carbon Number Concept

The decreasing molar flame ionization detector response with the increasing length of the polyethylene oxide chain of three series of alkyl- and aryl-polyoxyethylene-trimethylsilyl ethers and a series of bis-trimethylsilylpolyoxyethylene ethers is described in terms of the effective carbon number (ECN) of each oligomer. When the ECN contribution of the -CH 2 -O-Si(CH 3 )3 group is assumed to be equivalent to 3.69 carbon atoms, the presence of each oxygen atom in the ethylene oxide chain is found to be equivalent to -0.41 ± 0.05 carbon atoms.

Mechanism of the flame ionization detector II. Isotope effects and heteroatom effects

The relative molar flame ionization detection (FID) response (RMR) for a hydrocarbon does not change when deuterium is substituted for hydrogen. The exception is methane for which an inverse deuterium isotope effect of 3.5% is observed for tetradeuteromethane. [ 13C]Methane shows an inverse isotope effect of 2%. The reason for the small or non-existent isotope effects is that H/ 2H exchange takes place in the pre-combustion hydrogenolysis in the flame. This was shown by taking samples from the lower part of the flame by means of a fused-silica capillary probe. By the same technique the hydrogenolytic reactions in the hydrogen flame of compounds added to the hydrogen gas in low concentrations were followed. Alcohols, ethers, ketones, and esters all produced methane and carbon monoxide, while amines produced methane and hydrogen cyanide, halogen compounds methane and hydrogen halide, etc. The FID response of an organic compound is the sum of the responses from the products formed in the hydrogenolysis.

Qualitative and Quantitative Determination of Methyl Esters, Free Fatty Acids, Mono-, Di-, and Triacylglycerols Via HPLC Coupled with a Flame Ionization Detector

High performance liquid chromatography (HPLC) with a cyanopropyl phase column coupled directly to a commercial HPLC flame ionization detector (FID) and a gradient mobile phase of tert-butyl ether and hexane proved successful to separate and quantitate mono-, di-, and triacylglycerols, free fatty acids and methyl esters. These components can occur together during glycerolysis, lipolysis, randomization, and interesterification reactions of vegetable oils like soybean. Gravimetric standards were evaluated by HPLC-FID in which each contained mono-, di, and triacylglyceols, free fatty acids and methyl esters of palmitic. stearic, oleic, linoleic, and linolenic acids respectively. The FID response with solute weight decreased in this order: triacylglycerols, free fatty acids, diacylglycerols, methyl esters, and monoacylglycerols, respectively. The FID thus required response factors to quantitate the components of mixtures of diverse lipid species. However, for homogenous compounds the FID response was linear and response factors were not required, for example, for a series of free fatty acids like palmitic through linolenic. The commercial HPLC-FID proved satisfactory for facile quantitation of diverse lipid species in vegetable oil reaction mixtures. Good accuracy was obtained by HPLC with FID for soybean glycerolysis products, which contained mono, di and triacylglycerols.

Environmental tobacco smoke (ETS): A market cigarette study

The environmental tobacco smoke (ETS) yield of selected analytes was determined for the 50 top-selling U.S. cigarette brand styles (1991) and the University of Kentucky Research cigarette, K1R4F. ETS was generated by smokers in an environmental test chamber. Analytes determined included real-time measurements of nicotine, 3-ethenylpyridine, respirable suspended particles (RSP), carbon monoxide, and total hydrocarbons by flame ionization detector response (FID). Real-time RSP values were determined independently by a piezoelectric balance and real-time aerosol monitor (RAM). Additional analytes determined on a time-integrated basis included: nicotine, 3-ethenylpyridine, myosmine, RSP, ultraviolet particulate matter (VUPM), fluorescent particulate matter (FPM), solanesol, scopoletin, formaldehyde, acetaldehyde, acetone, catechol, ammonia, 34 volatile organic compounds (VOCs), and total VOCs (estimated by GC/mass spectrometric response). In general, lowering mainstream tar resulted in lower ETS emissions. The current study showed that ETS-RSP and nicotine were not predictive of each other. In fact, this ETS market brand style comparison showed a poor relationship between ETS nicotine and ETS-RSP. ETS analyte yields are summarized by mainstream tar categories, and overall sales-weighted average yields are calculated. Sales-weighted average ETS-RSP yields for full flavor (FF), full flavor low tar (FFLT), and ultra low tar (ULT) were 14.86, 12.30, and 10.51 mg/cig, respectively. The average RSP yield for all cigarettes evaluated was 13.67 mg/cig. These results, based on 65.3% of the U.S. cigarette market, should enable better estimations of the contribution of ETS to indoor air.