Flame photometric detector, volatile compounds

The analysis of organosulphur compounds has been greatly facilitated by the flame photometric detector [2], Volatile compounds can be separated by a glass capillary chromatographic column and the effluent split to a flame ionization detector and a flame photometric detector. The flame photometric detector response is proportional to [S2] [3-6]. The selectivity and enhanced sensitivity of the flame photometric detector for sulphur permits quantitation of organosulphur compounds at relatively low concentrations in complex organic mixtures. The flame ionization detector trace allows the organosulphur compounds to be referenced to the more abundant aliphatic and/or polynuclear aromatic hydrocarbons. 

Lamkin et al. [276] studied in detail the GC analysis of silylated methylthiohydantoins of all protein amino acids. They effected the silylation with BSA-acetonitrile (1 3) at 100°C for 10 min. They separated the products in a simple column packed with 2% of OV-17 on Gas-Chrom Q at 145—230°C, and Fig. 5.20 illustrates the results. The authors used a flame photometric detector, sensitive to sulphur-containing compounds, in order to ensure sensitive and selective detection. Minor incidental peaks that were often noticed during the analysis of the samples obtained by the Edman degradation of proteins with the use of an FID did not appear and the peak of the solvent was not detected. The baseline stability was good and the response was linear over a range of two orders of magnitude of concentration. Asn and Phe were the only unresolved pair Arg, as in previous instances, did not form a volatile derivative. 

Jiemin, L., Ning, L., Meijuan, W., Guibin, J. Determination of volatile sulfur compounds in beverage and coffee samples by purge-and-trap on-line coupling with a gas chromatography-flame photometric detector. Microchim. Acta 148, 43 7 (2004)... 

Stevens, R.K., O Keefe, A.E. and Oilman, G.C., 1969. Absolute calibration of a flame photometric detector to volatile sulphur compounds at sub-parts per million levels. Env. Sci. Tech., 3 652-655. 

The use of the flame photometric detector in the sulfur-sensitive mode (attributed to the emission of S2 spectral species at 394 nm) is exemplified in measuring the sulfur-containing volatiles in physiological fluids [110], or breath of liver-disease patients [111]. A word of caution concerns the fact that co-eluting non-sulfur compounds may result in a diminished or quenched response of the measured species [112]. Hence, the need for maximum solute separation. The detector is responsive to nanogram amounts of sulfur-containing compounds, but the response increases with the square of sulfur content [112]. Merits of the flame photometric detector in the detection of phosphorus compounds is somewhat overshadowed by a similar capability of the thermionic detector. 

The analysis of volatile sulphur compounds is difficult as additional compounds may be formed if the sample is heated or exposed to light or oxygen. Headspace analysis by gas-liquid chromatography using a flame photometric detector is the most satisfactory technique although solvent extraction may be necessary for the less volatile compounds. The sulphur compounds which have been identified in beer are listed in Table 22.19. 

Sulfur compounds play a major role in determining the flavor and odor characteristics of many food substances. Often sulfur compounds are present in trace levels in foods making their isolation and quantification very difficult for chromatographers. This study compares three gas chromatographic detectors the flame photometric detector, sulfur chemiluminescence detector and the atomic emission detector, for the analysis of volatile sulfur compounds in foods. The atomic emission detector showed the most linearity in its response to sulfur the upper limit of the linear dynamic range for the atomic emission detector was 6 to 8 times greater than the other two detectors. The atomic emission detector had the greatest sensitivity to the sulfur compounds with minimum detectable levels as low as 1 pg. 

Aroma of muskmelon, sulfur volatile sensory evaluation by GC-olfactometry, 36-47 Aroma threshold, determination, 81 Aroma volatiles in meat, sulfur-containing, See Sulfur-containing aroma volatiles in meat Artifacts, sulfur compounds in foods, 3 Atomic emission detector comparison to flame photometric and sulfur chemiluminescence detectors, 17,21... 

Figure 128 shows the apparatus used by Braman and Tomkins which consists of a sample reaction chamber, U-trap, the flame emission type detector, and conventional type photometric readout and recording system. Inorganic and methyltin compounds in aqueous solution in the reaction chamber are reduced to stannane or the corresponding methylstannanes by treatment with sodium borohydride solution buffered at pH 6.5. Helium carrier gas scrubs the volatile stannanes out of solution and into the liquid nitrogen-cooled U-trap where they are frozen out. Upon removal of the liquid nitrogen and warming, the stannanes are separated and carried into the detector. 

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