Flame thermionic ionization detector

Flame-Ionization Detector or Flame-Thermionic Ionization Detector... 

Since the introduction of the Mark V latroscan model, there have been no further technical improvements to the TLC-FID system. However, the development of vapour phase detectors (such as the flame thermionic ionization detector for compounds containing nitrogen and halogens, and the flame emission photometric detector which detects compounds containing sulphur and phosphorus) should extend the range of applications of the TLC-FID system. 

Some recent developments involving the use of novel vapor phase detectors, such as the flame thermionic ionization detector (FTID), which responds to compounds containing nitrogen and halogen atoms, and the flame emission photometric detector (33), which detects substances containing sulfur and/or phosphorus as well as chemiluminescent nitrogen detector, coupled on-line with FID (33a), should be able to widen the range of possible applications of the coated rod TLC-FID systems. 

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], ... 

ECD = electron capture detection FID = flame ionization detector GC = gas chromatography MS = mass spectroscopy NSD = nitrogen specific detector TID = thermionic ionization detector... 

At the temperatures and pressures generally used in gas chromatography the common carrier gases employed behave as perfect insulators. In the absence of conduction by the gas molecules themselves, the increased conductivity due to the presence of very few charged species is easily measured, providing the low sample detection limits characteristic of ionization based detectors [259]. Examples of ionization detectors in current use include the flame ionization detector (FID), thermionic ionization detector (TID), photoionization detector (PID), the electron-capture detector (ECD), and the helium ionization detector (HID). Each detector employs a different method of ion production, but in all cases the quantitative basis of detector operation corresponds to the fluctuations of an ion current in the presence of organic vapors. 

Modem thermionic ionization detectors evolved out of earlier studies of alkali-metal-doped flame ionization detectors [253]. Adding an alkali metal salt to a flame enhanced the response of the detector to compounds containing certain elements, such as N, P, S, B, as well as some metals (e.g. Sb, As, Sn, Pb). In its early versions, however, the detector response was unreliable and critically dependent on experimental parameters. Recent studies involving the continuous introduction of alkali metal salt solutions or aerosols into the flame demonstrated more reliable performance but have not been taken up [268,269]. 

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. 

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. 

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,... 

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

The alkali flame ionization detector (AFID) or thermionic detector (TID) is a specific detector used primarily in the trace analysis of pesticides particularly those containing phosphorus. 

Nitrogen-phosphorus detector (NPD), thermionic detector, alkali flame ionization detector... 

The thermionic or alkali flame ionization detector (FID) is a variant of the FID that has enhanced sensitivity to nitrogen (N) and phosphorous (P) containing compounds. It is essentially a hydrogen flame around a pellet of an alkali metal salt with an electric potential across the flame. Organic compounds in the air are drawn into the flame and ionized. The alkali metal enhances the response to N and P-containing compounds and, since many chemical agents contain N and P, it is selective for their detection. This detector is rarely used without prior separation by GC. 

The NPD is similar in design to the FID (flame ionization detector), except that the hydrogen flow rate is reduced to about 3 mL/min, and an electrically heated thermionic bead (NPD bead) is positioned near the column orifice. Nitrogen or phosphorus containing molecules exiting the column collide with the hot bead and undergo a catalytic surface chemistry reaction. The resulting ions are attracted to a collector electrode, amplified, and output to the data system. The NPD is 10-100 times more sensitive than FID. 

The alkali flame-ionization detector, sometimes called an NP or nitrogen-phosphorus detector, contains a thermionic source, such as an alkali-metal salt or a glass element containing rubidium or other metal, that results in the efficient ionization of organic nitrogen and phosphorus compounds. It is a selective detector that shows little response to hydrocarbons. 

Ives and Guiflfrida ° investigated the applicability of the potassium chloride thermionic detector and the flame ionization detector to the determination of organoarsenic compounds in the presence of organophosphorus and nitrogen-containing compounds. 

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