Flame Photometric Detector The flame photometric detector was invented by Grant in the late 1950s for measuring the aromatic hydrocarbon content of benzole. In the manufacture of coal gas (either as a primary product from a town-gas works, or as a byproduct from a coke oven) the gas is scrubbed with oil and the benzole recovered from the oil by distillation. Benzole is a complex mixture of hydrocarbons, mostly aromatic, the majority of which is benzene. The product was a very valuable anti-knock agent when added to gasoline. Grant used hydrogen as the carrier gas and burnt the hydrogen from the chromatography column at a small jet similar to the flame thermocouple detector or the flame ionization detector. The light from the flame was focused on a photoelectric cell, the output from which was electronically modified and fed to a recorder. Any aromatic burning in the flame rendered it strongly luminous and, thus, the aromatic compounds could be selectively identified. The response of the detector was largely qualitative but by suitable calibration could be made quantitative.
Author: RPW Scott
Book:Gas Chromatography Detectors
Section:GC-Detectors Emissivity-or-Photometric-Detector
nbsp; Virtually all the basic drugs contain nitrogen and thus can be specifically detected among a large number of other unresolved compounds not containing nitrogen. The Emissivity or Photometric Detector The emissivity detector or, the Flame Photometric detector (FPD), was described by Grant (10) in 1958 but as it could not compete in sensitivity with the ionization detectors, did not raise any commercial interest. The emissivity detector, however, has some unique properties that could make its response quite specific and giving it certain unique areas of application. It was originally used to differentiate aromatic from paraffinic hydrocarbons by measuring the luminosity that the aromatic nucleus imparted to the flame. Contemporary photometric detectors do not usually monitor the total light emitted only light emitted at specific wavelengths. For example, phosphorus and sulfur containing hydrocarbons generate chemi-
Author: RPW Scott
Book:Gas Chromatography Detectors
Section:GC-Detectors Emissivity-or-Photometric-Detector
, the emission from the background hydrocarbons is very small (albeit around a minor transmission maximum). Similarly, the light emit by phosphorus compounds lies between 480 nm and 580 nm. Thus, a filter having a transmission window between 520 nm and 560 nm, phosphorus compounds can be selectively sensed, and the emission from the background hydrocarbons will, again, be almost negligible. Thus, sulfur and phosphorus compounds can be selectively detected. A diagram of the Hewlett-Packard flame photometric detector is shown in figure 26. Courtesy of the Hewlett–Packard Corporation Figure 26 The Hewlett–PackardFlame Photometric Detector
