Flame-photometric detector FPD

This type of detector is frequently used in pesticide-residue analysis because of its high specificity and selectivity and its high sensitivity to sulphur and phosphorus compounds. In the arrangement devised by Brody and Cheney the radiation from a hydrogen-air flame is directed to a photomultiplier through an interference filter. Measurements are taken 

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The flame-photometric detector (FPD) is selective for organic compounds containing phosphoms and sulfur, detecting chemiluminescent species formed ia a flame from these materials. The chemiluminescence is detected through a filter by a photomultipher. The photometric response is linear ia concentration for phosphoms, but it is second order ia concentration for sulfur. The minimum detectable level for phosphoms is about 10 g/s for sulfur it is about 5 x 10 g/s. 

Flame Photometric Detector3 With the flame photometric detector (FPD), as with the FID, the sample effluent is burned in a hydrogen/air flame. By using optical filters to select wavelengths specific to sulfur and phosphorus and a photomultiplier tube, sulfur or phosphorus compounds can be selectively detected. 

GC nitrogen-phosphorus detector (NPD), flame photometric detector (FPD), electron capture detector (BCD), flame ionization detector (FID), mass-spectrometric detector (MS)... 

The chemiluminescent reaction with chlorine dioxide provides a highly sensitive and highly selective method for only two sulfur compounds, hydrogen sulfide and methane thiol [81]. As in the flame photometric detector (FPD), discussed below, atomic sulfur emission, S2(B3S -> ) is monitored in the wave-... 

Schematic cross-section of a flame photometric detector (FPD).

Brody and Chaney in 1966, were the first and foremost to describe the flame photometric detector (FPD) which unfortunately could not get enough recognition in the field of gas chromatographic analysis due to the following reasons, namely ... 

Sulfur Dioxide. Both flame photometric and pulsed fluorescence methods have been applied to the continuous measurement of S02 from aircraft. In the flame photometric detector (FPD), sulfur compounds are reduced in a hydrogen-rich flame to the S2 dimer. The emission resulting from the transition of the thermally excited dimer to its ground state at 394 nm is measured by using a narrow band-pass filter and a photomultiplier tube. 

The impact of the flame photometric detector (FPD) resides in its simultaneous sensitivity and specificity for the determination of sulfur and phosphorus. It is inherently compatible with the FID and as such affords the analytical chemist a discriminating ability beneficial to many analyses. In 1966, Brody and Chaney published data on their design of an FPD (26)(Figure 5.18). 

Organochlorine pesticides and OPPs have been determined mainly using GC, because of the stability and volatility that most of them show under chromatographic conditions and, particularly, the availability of element-selective detectors that display high selectivity for OCPs (electron-capture detector, ECD), and OPPs (flame photometric detector, FPD, and nitrogen phosphorus detector, NPD). Mass spectrometry-based detection is also more popular in GC than in HPLC (1,2,12,16). 

Instrument and column conditions. A Tracor 222 gas chromatograph equipped with a flame photometric detector (FPD) operating in the phosphorus mode (526 mu) filter was used. The operating conditions of the flame photometric gas chromatographic analyses were as follows ... 

Extracted coals from eastern Oklahoma were analyzed using pyrolysis-gas chromatography and a flame photometric detector (FPD) to characterize the organosulfur compounds produced by pyrolysis of coals. All coals from the Croweburg seam with calorific values below 13,000 BTU (Table I) were shown to produce similar distributions of organosulfur compounds. The ratio of dibenzothiophenes to thiophenes produced by pyrolysis was shown to be proportional to the calorific value of the coal. 

Furthermore, GC samples were separated on a Carlo Erba type 4200 gas chromatograph fitted with a normal FID and with a flame photometric detector (FPD) operating in the sulfur-mode at 394 nm. Again, the dead-volume free "glass-cap-cross" was used in order to split the carrier gas flow. By means of these sulfur chromatograms mass spectral evaluation could be focussed on certain compounds in very complex mixtures. 

Most OP insecticides may be determined directly by GC using the phosphorus-selective flame photometric detector (FPD) which helps to minimize clean-up. However, it must be emphasised that the FPD is only a "selective" detector for phosphorus (at 540 nm) or sulphur (at 394 nm) and not an "element specific detector". 

The non-polar chlorinated hydrocarbon pesticides are routinely quantified using gas chromatography (GC) and electron capture(EC) detection. Alternate detectors include electrolytic conductivity and microcoulometric systems. Organophosphate pesticides which are amenable to GC are responsive to either the flame photometric detector (FPD) or the alkali flame detector (AFD). Sulfur containing compounds respond in the electrolytic conductivity or flame photometric detectors. Nitrogen containing pesticides or metabolites are generally detected with alkali flame or electrolytic conductivity detectors. 

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