Detectors sulfur chemiluminescence

Figure 14.2 Schematic diagram of the cliromatographic system used for the analysis of low concenti ations of sulfur compounds in ethene and propene VI, injection valve V2, column switcliing valve SL, sample loop R, restriction to replace the column SCD, sulfur chemiluminescence detector.

The System described in the previous section has been extended with a sulfur chemiluminescence detector (SCO) for the detection of Sulfur compounds (32). The separated fractions were thiols + sulfides + thiophenes (as one group), benzothio-phenes, dibenzothiophenes and benzonaphtho-thiophenes. These four groups have been subsequently injected on-line into and separated by the GC unit. Again, no overlap between these groups has been detected, as can be seen from Figure 14.20, in which the total sulfur compounds are shown and from Figure 14.21 in which the separated dibenzothiophenes fraction is presented. The lower limit of detection of this method proved to be 1 ppm (mg kg ) sulfur per compound. 

SCD Sulfur chemiluminescence detector (flame and flameless) Ozone-induced CL... 

Many sophisticated analytical techniques have been used to deal with these complex mixtures.5,45,46 A detailed description is not possible here, but it can be noted that GLC, often coupled with mass spectrometry (MS), is a major workhorse. Several other GLC detectors are available for use with sulfur compounds including flame photometer detector (FPD), sulfur chemiluminescence detector (SCD), and atomic emission detector (AED).47 Multidimensional GLC (MDGC) with SCD detection has been used48 as has HPLC.49 In some cases, sniffer ports are provided for the human nose on GLC equipment. 

The chemiluminescent reaction of SO with ozone is the basis of the sulfur chemiluminescence detector (SCD) [23] discussed later in this chapter,... 

Elemental composition C 15.77%, S 84.23% carbon disulfide. It may be analyzed by GC using a sulfur chemiluminescence detector or by GC/MS. A concentration of 1 ppm in the air may be measured by mass spectrometry. The primary characteristic ionic mass for identification of this compound by mass spectrometry is 76. Many GC columns are available commercially. 

Elemental composition H 5.92%, S 94.08. Hydrogen sulfide may be distinguished by its characteristic odor. The gas turns a paper soaked in lead acetate solution black. Many infrared sensors are commercially available for in-situ measurements of H2S. It may be monitored semiquantitatively by Draeger tubes. It also may be analyzed by GC following trapping over molecular sieves and thermal desorption. Either a flame photometric detector or a sulfur chemiluminescence detector may be used for GC analysis. It may be separated on a capillary column such as Carboxen 1006 PLOT or SPB-1 SULFUR (Supelco Catalog 1999 Supelco Inc., BeUefonte, PA). 

Figure 24-20 Gas chromatograms showing sulfur compounds in natural gas (o) flame ionization detector response and (b) sulfur chemiluminescence detector response. The organosulfur compounds are too dilute to be seen in flame ionization, and the sulfur chemiluminescence is insensitive to hydrocarbons. [From N. G. Johansen and J. W. Birks, Determination of Sulfur Compounds in Difficult Matrices." Am. Lob. February 1991.112.]...

An alternative to FPD in the sulfur mode is the sulfur chemiluminescence detector (SCD) (48). This detector works by forming sulfur monoxide in a reducing flame. Sulfur monoxide is detected by its chemiluminescent reaction with ozone. The SCD is at least one order of magnitude more sensitive than most FPDs. It provides a linear response with high selectivity and does not suffer considerably from quenching. 

Burmeister, M.S., Drummond, C.J., Pfisterer, E.A. and Hysert, D.W. (1992) Measurement of volatile sulfur compounds in beer using gas chromatography with a sulfur chemiluminescence detector,/. Am. Soc. Brew. Chem., 50(2), 53-58. 

Sulfur-containing components exist in gasoline-range hydrocarbons and can be identified with a gas chromatographic capillary colunm coupled with either a sulfur chemiluminescence detector or an atomic emission detector (AED) (ASTM D-5623). The most widely specified method for total sulfur content uses X-ray spectrometry (ASTM D-2622), and other methods that use ultraviolet fluorescence spectroscopy (ASTM D-5453) and/or hydrogenolysis and colorimetry (ASTM D-4045) are also apphcable, particularly when the sulfur level is low. 

Tang, H. M., Heaton, P., and Brassard, B., Analysis of trace COS in samples with high concentrations of H2S hy gas chromatography and a sulfur chemiluminescence detector. Field Anal. Chem. Technol., 1, 171-174, 1997. 

Chen, Y. C. and Lo, J. G., Gas chromatography with flame ionization and flameless sulfur chemiluminescence detectors in series for dual channel detection of sulfur compounds, Chromatographia, 43, 522-526, 1996. 

Several other types of GC detectors are useful for specific applications. The sulfur chemiluminescence detector is based on the reaction between certain sulfur compounds and o/.one. 1 he resulting luminescence... 

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