Ionization detector electron capture

Elimination of wet chemical sample preparation enables a complete analysis to be performed and data to be quickly analyzed. The detection limits are in the low part-per-million range using mass spectrometric detection. Alternatively, detection of compounds can be achieved by all common gas chromatography detectors (flame ionization detector, electron capture detector and flame photometric detector), and detection limits are determined by the method of detection employed. 

Match the detector with the items that follow thermal conductivity detector, flame ionization detector, electron capture detector, and mass spectrometer detector. 

The eluted components go to the detector of the gas chromatograph. The most commonly used detectors are thermal conductivity detector, flame ionization detector, electron capture detector, atomic emission detector, IR, ion trap detector, and MS. The detected components are processed by an integrator and appear on chart papers as a series of peaks on a time scale. The chart is called a gas chromatogram. 

There are different types of detectors, including thermal conductivity and electron capture types. The most common detector is flame ionization variety (FID). A hydrogen flame is utilized to combust the column effluents. Thermal conductivity detectors do not degrade the effluents and are not as sensitive as flame ionization detectors. Electron capture detection is especially sensitive to halogenated compounds. 

Pressures Helium—60 psig, Hydrogen—10 psig Quantitative determinations of purity were made at the Analytical Laboratory of Dow Chemical Co. by GLC using flame ionization and electron capture detectors. Unknown samples were compared with prepared standards containing the compounds in question. 

Of the thermal conductivity, flame ionization, and electron capture detectors, which... 

AOAC = Assocition of Official Analytical Chemists ASTM = American Society for Testing and Materials Cl = chemical ionization ECD = electron capture detection ELCD = electrolytic conductivity detector EPA = Environmental Protection Agency GC = gas chromatography GPC = gel permeation chromatography ... 

Instrumentation. Preliminary gas chromatographic analyses were carried out on a Perkin-Elmer 900 gas chromatograph equipped with a flame ionization detector and on a Hewlett-Packard 5730A gas chromatograph equipped with flame ionization and electron-capture detectors. The columns used were 180 cm x 2 mm ID glass columns packed with 3% SL-2100 (a methyl silicone fluid) on 80/100 mesh Supelcoport we also used 25 m X 0.25 mm ID glass capillary columns statically coated (7) with SE-52. 

A final point about factors. They need not be continuous random variables. A factor might be the detector used on a gas chromatograph, with values flame ionization or electron capture. The effect of changing the factor no longer has quite the same interpretation, but it can be optimized— in this case simply by choosing the best detector. 

MS, Mass spectrometry El, electron impact Cl, chemical ionization MID, multiple ion detection PICI, positive-ion chemical ionization NICI, negative-ion chemical ionization SIM, selected ion nmonitoring TSP, thermospray PPINICI, pulsed positive ion-negative ion chemical ionization ECD, electron-capture detector NPD, nitrogen/phosphorous detector NSTD, nitrogen-selective thermionic detector FT-IR, Fourier transform infrared spectrometry. 

The function of the detector is to sense and respond with an electrical signal when the composition of the gas emerging from the column changes. The type of detector used is dependent on the application. The most widely used detectors are the thermal conductivity, flame ionization, and electron capture. 

DISCUSSION. Figure 10.11 shows the separation of a group of gases from blood. The procedure described depends on complete equilibration between the gas and liquid in the syringe. The period to achieve equilibration depends on the gas, and can be as little as 1 min for acetone and as much as 30 min for sulfur hexafluoride. Linear calibration curves can be obtained when peak height is plotted against gas concentration for either the flame ionization or electron capture detector. The reproducibility (n = 10) for ethane gave a standard deviation of 23% of the mean concentration while it was 2.3% for halothane and 1.8% for ether. 

Gas chromatography is a technique utilized for separating volatile substances (or those that can be made volatile) between two phases, one of which is a gas. Purge-and-trap methods are frequently used for trace analysis. Various detectors have been employed in trace analysis, the most commonly used being flame ionization and electron capture detectors. 

Both packed and capillary columns are used with the SFE-GC tandem. The detector is usually of the mass spectrometry, flame ionization or electron capture type. The most suitable interface for each application will be that allowing the extractant to be removed prior to the column — and hence to the detector. 

The key sample set selection for analytical method development has been discussed at length in Chapter 7. There are a great variety of methods used for monitoring impurities.1,2 The primary requirement for such techniques is the capacity to differentiate between the compounds of interest. This requirement frequently necessitates utilization of separation methods (covered in Section V. C) in combination with a variety of detectors (Section V. B). For gas chromatography, flame ionization and electron capture detectors are commonly used. However, these detectors are not suitable for isolation and characterization of impurities, which require... 

Apparatus Barber-Colman Model 5000 fitted with both flame ionization and electron-capture detectors. 

For the GC method, 0-(2,3,4,5,6-pentafluorobenzyl)hydroxylamine can be detected by flame ionization detector, MS/SIM detector, electron-capture detector, or flame photometric detector. 1,2-Diaminobenzene derivatives of MG can be analyzed using a flame ionization detector, MS/SlM, or a specific nitrogen/phosphorus... 

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. 

Describe the principles of the following gas chromatography detectors (a) thermal conductivity, (b) flame ionization, (c) electron capture. 

Information for acertain parameter not available, if not given, na, not available DI, deionized water Cl, chemical ionization BCD, electron capture detector El, electron impact ionization FID, flame ionization detector MS, mass spectrometer MtBE, methyl tert-butylether MTBSTE, n-(tert-butyldimethylsilyl)-Wmethylfluoracetamide PDAM, 1-pyrenyldiazomethane PFBBr, pentafluorobenzyl bromide PEBOH, pentafluorobenzyl alcohol SPME, solid-phase microextraction TOPO, tri-n-octylphoshine oxide UASB, upflow anaerobic sludge blanket reactor. 

The three most common detectors in gas chromatography are those using thermal conductivity, flame ionization, and electron capture. The first is also the oldest it measures heat conductivity, which is different for different gases. The second and third types respond to changes in electron currents the electrons are produced in a flame by burning the sample, or by exposing the sample to a radioactive source. 

APCI = negative ion atmospheric pressure chemical ionization ECD = electron capture detector GC = gas chromatography HPLC = high performance liquid chromatography HRGC = high resolution gas chromatography MS = mass spectrometry... 

Laboratory air is routinely monitored quarterly by the NIOSH charcoal tube sampling procedure. Laboratory air is drawn through the tube for an 8 hour period and the charcoal adsorbant is extracted with carbon disulfide or other suitable solvents. The extract is analyzed by gas chromatography using both flame ionization and electron capture detectors. Chromatograms from each sample are compared to those of blank samples collected prior to initiation of Hazardous Materials Laboratory operations. Standard analytical techniques (HPLC, GC/MS, etc.) are used, as required, for identification, confirmation and quantitation. 

For GC the mycotoxins need to be sufficiently thermostable and volatile to be converted into volatile derivatives. The most widely used detectors in mycotoxin GC analysis are flame ionization (FID), electron capture (BCD), and mass spectrometry (MS). These do not require that a compound show any fluorescence or UV absorption and the groups of mycotoxins for which GC is the most suited are the trichothecenes and the fumonisins. 

A wide variety of HPLC detectors have been developed to try to fill both the high-sensitivity and universal-detection requirements. Some of these are adaptations of well-known GC detectors such as flame ionization and electron capture. This discussion will focus primarily on the design and appropriate applications of the seven most common and commercially available HPLC detectors. A listing of these detectors is shown in Table II. The HPLC detectors can generally be classified as either responsive to a change in the property of the mobile phase when a solute (sample component) is present or to a property of the actual solute itself. 

The chromatogram can finally be used as the series of bands or zones of components or the components can be eluted successively and then detected by various means (e.g. thermal conductivity, flame ionization, electron capture detectors, or the bands can be examined chemically). If the detection is non-destructive, preparative scale chromatography can separate measurable and useful quantities of components. The final detection stage can be coupled to a mass spectrometer (GCMS) and to a computer for final identification. 

---