Flame thermionic detector

SPME has been utilized for deterrnination of pollutants in aqueous solution by the adsorption of analyte onto stationary-phase coated fused-siUca fibers, followed by thermal desorption in the injection system of a capillary gas chromatograph (34). EuU automation can be achieved using an autosampler. Eiber coated with 7- and 100-p.m film thickness and a nitrogen—phosphoms flame thermionic detector were used to evaluate the adsorption and desorption of four j -triazines. The gc peaks resulting from desorption of fibers were shown to be comparable to those obtained using manual injection. 

Hewlett-Packard Model 6890 gas chromatograph with capillary split/splitless inlet with HP5973 mass-selective detector equipped with an autosampler Shimadzu GC17A gas chromatograph with capillary split/splitless inlet with flame thermionic detector equipped with an AOC-17 autoinjector... 

Shimadzu GC-7A gas chromatograph with flame thermionic detector Pyrex spiral column packed with 3% OV-1 on Gas Chrom Q (80-100 mesh), 1 m X 3-mm i.d. 

Gas chromatograph equipped with a flame thermionic detector High-performance liquid chromatograph... 

Shinohara et al. [299] have described a procedure based on gas chromatography for the determination of traces of two, three, and five-ring azarenes in seawater. The procedure is based on the concentration of the compounds on Amberlite XAD-2 resin, separation by solvent partition [300], and determination by gas chromatography-mass spectrometry with a selective ion monitor. Detection limits by the flame thermionic detector were 0.5-3.0 ng and those by gas chromatography-mass spectrometry were in the range 0.02-0.5 ng. The preferred solvent for elution from the resin was dichloromethane and the recoveries were mainly in the range 89-94%. 

Figure 14. Chromatograms of organophosphorus pesticides obtained from a small-bore fused silica column (0.2 mm i.d., 1 m long) packed with 5-pm Spherisorb ODS. A, UV detection at 254 nm and B, dual-flame thermionic detector. Peaks correspond to 1, solvent containing phosphorus impurities 2, guthion, 89 ng of phosphorus 3, zolone, 71 ng of phosphorus and 4y ethion, 144 ng of phosphorus. Mobile-phase conditions 15% water and 85% methanol (v/v) at a flow rate of 1.6 pL/min. (Reproduced from reference 58. Copyright 1983 American Chemical Society.)...

Fourier transform flame thermionic detector Fourier transform infrared full width at half maximum... 

The conventional sensitive and specific GC detection such as electron-capture detector (BCD) (see Fig. 2), flame thermionic detector (FTD), and flame photometric detector (FPD) are still widely used in pesticide residue analysis. In recent years, mass spectrometric detection is becoming more and more important. Although other types of mass analyzers are commercially available, the equipment used in modern residue laboratories is based on two major types the classical quadrupole mass analyzers and those based on the ion trap (also called tridimensional quadrupole). 

Detectors are either concentration sensitive or mass flow sensitive. The signal from a concentration-sensitive detector is related to the concentration of the solute in the detector and is decreased by dilution with a makeup gas. The sample is usually not destroyed. Thermal conductivity, argon-ionization, and electron capture detectors are concentration sensitive. In mass-flow-sensitive detectors, the signal is related to the rate at which solute molecules enter the detector and is not affected by the makeup gas. These detectors usually destroy the sample, such as flame ionization and flame thermionic detectors. Sometimes two-column GC is used to increase resolution, by taking cuts of eluents from an initial column and directing them to a second column for secondary separation. The first detector must be nondestructive or else the eludnt split prior to detection, with a portion going to the second column. 

Risner, C. H. and Corner, J. M., A quantification of 4- to 6- ring polynuclear hydrocarbons in indoor air samples by high-performance liquid chromatography, Environ. Toxicol. Chem., 10, 1417-1423, 1991. Yamamoto, N., Nishiura, H., Honjo, T., and Inoue, H., Determination of ammonia in the atmosphere by gas chromatography with a flame thermionic detector. Anal. Sci., 7, 1041-1044, 1991. 

When this detector was invented by Karmen and Giuffrida in 1964 [26] it was known as the alkali flame ionization detector (AFID) because it consisted of an FID to which was added a bead of an alkali metal salt. As it has continued to evolve, its name has also changed and it has been known as a thermionic ionization detector (TID), a flame thermionic detector (FTD), a thermionic specific detector (TSD), etc. 

Other Detectors Two additional detectors are similar in design to a flame ionization detector. In the flame photometric detector optical emission from phosphorus and sulfur provides a detector selective for compounds containing these elements. The thermionic detector responds to compounds containing nitrogen or phosphorus. 

The alkah flame-ionisation detector (AFID), sometimes called a thermionic (TID) or nitrogen—phosphoms detector (NPD), has as its basis the fact that a phosphoms- or nitrogen-containing organic material, when placed ia contact with an alkaU salt above a flame, forms ions ia excess of thermal ionic formation, which can then be detected as a current. Such a detector at the end of a column then reports on the elution of these compounds. The mechanism of the process is not clearly understood, but the enhanced current makes this type of detector popular for trace analysis of materials such as phosphoms-containing pesticides. 

Ionisation detectors. An important characteristic of the common carrier gases is that they behave as perfect insulators at normal temperatures and pressures. The increased conductivity due to the presence of a few charged molecules in the effluent from the column thus provides the high sensitivity which is a feature of the ionisation based detectors. Ionisation detectors in current use include the flame ionisation detector (FID), thermionic ionisation detector (TID), photoionisation detector (PID) and electron capture detector (ECD) each, of course, employing a different method to generate an ion current. The two most widely used ionisation detectors are, however, the FID and ECD and these are described below. 

The most common selective detectors in use generally respond to the presence of a characteristic element or group in the eluted compound. This is well illustrated by the thermionic ionisation detector (TID) which is essentially a flame ionisation detector giving a selective response to phosphorus- and/or nitrogen-containing compounds. Typically the TID contains an electrically heated rubidium silicate bead situated a few millimetres above the detector jet tip and below the collector electrode. The temperature of the bead is maintained... 

One great advantage of GC is the variety of detectors that are available. These include universal detectors, such as flame ionization detectors and selective detectors, such as flame photometric and thermionic detectors. The most generally useful detectors, excluding the mass spectrometer are described in the following sections. 

EC = electrical conductivity detector ECD = electron capture detector FPD = flame photometric detector GC = gas chromatography HPLC = high performance liquid chromatography NPD = nitrogen phosphorus detector TID = thermionic detector UV = ultraviolet spectroscopy... 

The flame ionization detector Is the most popular of the flame-based detectors. Apart from a reduction in sensitivity compared to expectations based on gas chromatographic response factors [138] and incompatibility with the high flow rates of conventional bore columns (4-5 mm I. 0.), the flame ionization detector is every bit as easy to use in SFC as it is in gas chromatography [148,149]. It shows virtually no response to carbon dioxide, nitrous oxide and sulfur hexafluoride mobile phases but is generally incompatible with other mobile phases and mixed mobile phases containing organic modifiers except for water and formic acid, other gas chromatographic detectors that have been used in SFC include the thermionic ionization detector (148,150], ... 

To improve the detectability of silyl ethers, silylation reagents containing an electron-capturing group [443,449-451,468] or cyano group for thermionic detection [469] have been prepared, the 2-cyanoethyldimethylsilyl derivatives are only marginally aore sensitive (ca. 5 fold) to the thermionic detector than to the flame ionization det ftpr which Units their usefulness. The... 

GC is coupled with many detectors for the analysis of pesticides in wastewater. At the present time the most popular is GC-MS, which will be discussed in more detail later in this section. The flame ionization detector (FID) is another nonselective detector that identifies compounds containing carbon but does not give specific information on chemical structure (but is often used for quantification because of the linear response and sensitivity). Other detectors are specific and only detect certain species or groups of pesticides. They include electron capture,nitrogen-phosphorus, thermionic specific, and flame photometric detectors. The electron capture detector (ECD) is very sensitive to chlorinated organic pesticides, such as the organochlorine compounds (OCs, DDT, dieldrin, etc.). It has a long history of use in many environmental methods,... 

In both systems the flow of helium carrier gas through the columns was 0.7-0.8 ml min-1, with a septum purge of 0.5 ml min-1 and a split valve flow of 4-4.5 ml min-1. The injection ports were maintained at 260°C and the detector ovens at 240° C. The detector employed was either a flame ionisation or a nitrogen-specific NPD-40 thermionic detector (Erba Science (UK) Ltd) and the output was recorded on a HP 3390 integrator (Hewlett Packard Ltd, Wokingham, UK). 

Pesticides and Fungicides. Modern pure food regulations require that the food processor be responsible for their finished products. Since so many pesticides and fungicides are used in agriculture, their detection and quantitative analysis are difficult (5, 22). Organophosphorus and chlorinated hydrocarbons are the most common pesticides. When GLC is used for halogens, electron capture or microcoulometric detectors are used for phosphorus, a thermionic flame photometric detector is required. 

ALKALI FLAME IONIZATION DETECTOR (AFID)/THERMIONIC.. . 269... 

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