FID Characteristics

Nearly universal (all carbon compounds except CO, CO2, and HCN, bnt not many inorganic gases) destructive mass-flow detector needs H2 and air or O2 aux. gas sensitive with wide dynamic range. 

Capillary colunm carrying mobile phase (helium) 

---

Galacturonic acid, characterized, 739 Gas chromatography (GC) flame ionization detection (FID) characteristics of, 449 cholesterol, 461... 

An alternative procedure rescales the coordinates of each atom at each time step [24]. The atomic coordinate x and the characteristic distance for repeating boundary conditions, d, are rescaled to values uc and fid, respectively, where... 

Sotolon (4,5-dimethyl-3-hydroxy-2(5H)-furanone) and solerone (4-acetyl- y-butirrolactone) were claimed to be responsible for some aroma characteristic of flor sherries wines. These compounds are present only as traces, and are chemically unstable. A system of two gas chromatographs coupled with a four-port switching valve was used to quantitate these components without previous fractionation. The first chromatograph was equipped with an on-column injector, in order to avoid thermal degradation of sotolon in the heated injector, a DB-5 column and an FID. The second chromatograph was equipped with an on-column injector, a DB-1701 column and an FID. The method allowed quantification of solerone and sotolon at concentrations as low as a few ppb (29). 

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. 

Table 4.23 shows the main characteristics of advanced GC. The use of FID coupled to a high-efficiency capillary column is sufficient to perform routine additive analysis in the 20 ppm concentration range in solution. With adjustment of injection volume in an on-column injector the detection levels surpass... 

The zincblende (ZB), or sphalerite, structure is named after the mineral (Zn,Fe) S, and is related to the diamond structure in consisting entirely of tetrahedrally-bonded atoms. The sole difference is that, unlike diamond, the atoms each bond to four unlike atoms, with the result that the structure lacks an inversion center. This lack of an inversion center, also characteristic of the wurtzite structure (see below), means that the material may be piezoelectric, which can lead to spurious ringing in the free-induction decay (FID) when the electric fields from the rf coil excite mechanical resonances in the sample. (Such false signals can be identified by their strong temperature dependence due to thermal expansion effects, and by their lack of dependence on magnetic field strength). 

A stream-splitter may be used at the end of the column to allow the simultaneous detection of eluted components by destructive GC detectors such as an FID. An alternative approach is to monitor the total ion current (TIC) in the mass spectrometer which will vary in the same manner as the response of an FID. The total ion current is the sum of the currents generated by all the fragment ions of a particular compound and is proportional to the instantaneous concentration of that compound in the ionizing chamber of the mass spectrometer. By monitoring the ion current for a selected mass fragment (m/z) value characteristic of a particular compound or group of compounds, detection can be made very selective and often specific. Selected ion monitoring (SIM) is more sensitive than TIC and is therefore particularly useful in trace analysis. 

No other detector till date has surpassed the flame ionization detector (FID) as a universal gas chromatographic detector. It hardly meets, all the characteristic features of TCD in terms of simplicity, stability, and versatility besides having two distinctly positive plus points ... 

In many of these descriptions of lineshapes, chemical exchange line-shapes are treated as a unique phenomenon, rather than simply another example of relaxation effects on lineshapes. This is especially true for line-shapes in the intermediate time scale, where severe broadening or overlapping of lines may occur. The complete picture of exchange lineshapes can be somewhat simplified, following Reeves and Shaw [13], who showed that for two sites, the lineshape at coalescence can always be described by two NMR lines. This fact can be exploited to produce a clarified picture of exchange effects on lineshapes and to formulate a new method for the calculation of exchange lineshapes [16, 23]. This method makes use of the fact that lineshapes, even near coalescence, retain Lorentzian characteristics [13] (fig. 3). These lines, or coherences, are each defined by an intensity, phase, position, and linewidth, and for each line in the spectrum, the contribution of that particular line to the overall free induction decay (FID) or spectrum can be calculated. 

Carbon dioxide may be readily analyzed by various instrumental techniques, such as IR, GC, and GC/MS. Many portable infrared analyzers are available commercially for rapid, on site monitoring of CO2. Also, it can be analyzed by GC using a TCD or an FID. It readily may be identified by mass spectrometry from its characteristic ionic mass 44. Dissolved CO2 in water... 

Elemental composition C 42.88%, O 57.12%. Carbon monoxide may be identified and determined quantitatively at low ppm level by infrared sensors. Such CO detectors are commercially available. Also, it can be analyzed by GC using TCD or FID or by GC/MS. The characteristic ion mass for CO identification is 28 (same as N2 or ethylene, both of which can interfere). 

Elemental composition C 7.81%, Cl 92.19%. Carhon tetrachloride may be analyzed by GC or GC/MS. For GC determination, an FID or a halogen-specific detector such as ECD or HECD may he used. Trace concentrations in aqueous matrix or soil, sediments or sohd wastes may he determined by purge and trap or thermal desorption techniques followed hy GC or GC/MS measurements. The characteristic masses for identification of CCI4 by GC/MS are 117, 119 and 121. 

Elemental composition C 18.19%, F 57.57%, O 24.24%. Carbonyl fluoride may be analyzed by FTIR, GC or GC/MS. For the GC analysis, it may be transported with the carrier gas helium from the reaction vessel into a cryo-genically cooled injector port, then thermally desorbed and analysed by FID. The system should be free of moisture. The characteristic ions for mass spectroscopic identification are 66, 26, and 40. 

Elemental composition H 3.73%, C 44.44%, N 51.83%. HCN may be analyzed by GC or GC/MS. The aqueous solution may be directly injected onto the GC column and determined by an FID. For GC/MS determination, an alcoholic solution may be injected into the column. The characteristic mass ions are 27 and 26. The cyanide ion in aqueous solution also may be measured by cyanide ion-selective electrode, titrimetry, and by colorimetric methods (APHA, AWWA, WEF. 1999. Standard Methods for the Examination of Water and Wastewater, 20th ed. Washington, DC American Public Health Association). For colorimetric analysis, the aqueous solution may be treated with a dilute caustic soda solution, followed by treatment with chloramine-T, and then with pyridine-barbituric acid reagent. A red-blue color develops, the absorbance of which is measured by spectrophotometer at 578 nm. The concentration of CN is determined from a standard cahbration curve using KCN standards. 

The gas is adsorbed over activated characoal by sampling air. It is then desorbed out from charcoal with hexane or toluene and analyzed by GC-FID or GC/MS. Characteristic masses are 98, 100, 102, 63, 65. 

Attention With spectra measured on spectrometers equipped with digital filters (DMX, DRX spectrometers), the automatically performed phase correction (DMX Phase Corr.) will be applied twice when the newly created FID is Fourier transformed again. This will introduce the baseline roll characteristic for the data of these type of spectrometers. A first order phase correction must then be performed manually by setting the PHCl value close to -22000 for the data available in the NMR data base. 

Resampling with the Same Resin. Resin cleaning was performed to produce the minimum number of GC-FID responses from the cleaning solvent. One cycle of exposure to a sample of water followed by elution of the columns caused the reappearance of the characteristic contaminants, which have been tentatively identified by GC-MS as methyl benzoate, C2-benzaldehyde, C2-acetophenone, and the unknown listed in Table II and shown in Figures 4 and 5. A similar phenomenon also has been reported by Bean et al. (16) and Care et al. (22). 

The characteristics, advantages, and disadvantages of the Iatroscan TLC-FID system are fully discussed in this reference. It also contains rich information on the applications of the Iatroscan TLC-FID system in the area of lipids. 

FD. see Field desorption Fermentation, beer, 95 Ferrous oxidation/xylenol orange (FOX) method, lipid peroxide value (PV) basic protocol, 520-522, 526 characteristics of, 515, 526 modified, 527-528 FID. see Flame ionization detection Filtration, starch isolation, 676 Fish muscle, water retention examples, 320-323 (figs.) methods, 315-323... 

---