Sulfur compounds analysis methods

Table 4 summarises the p>arameters obtained from the calibration graphs for all of the reductive sulfur analytes, along with the method detection and quantification limits for each compoimd. Linear regression analysis revealed that very good linearities (R > 0.992) were obtained in the calibration graphs for all of the reductive sulfur compounds. The method provided very good detection limits, which were well below the sensory thresholds (See Table 1) of the analysed sulfur compounds. 

Analytical Methods. A method has been described for gas chromatographic analysis of trichloromethanesulfenyl chloride as well as of other volatile sulfur compounds (62). A method has been recommended for determining small amounts of trichloromethanesulfenyl chloride in air or water on the basis of a color-forming reaction with resorcinol (63). 

Puacz et al. (1995) developed a catalytic method, based on the iodine-azide reaction, for the determination of hydrogen sulfide in human whole blood. The method involves the generation of hydrogen sulfide in an evolution-absorption apparatus. In addition, the method allows for the determination of sulfide in blood without interference from other sulfur compounds in blood. A detection limit of 4 g/dm3 and a percent recovery of 98-102% were achieved. Although the accuracy and precision of the catalytic method are comparable to those of the ion-selective electrode method, the catalytic method is simpler, faster, and would be advantageous in serial analysis. 

In addition to chemical correlations discussed above, several physical methods are now available for the determination of the relative and absolute configurations of chiral sulfur compounds. Among these, NMR, infrared (IR), optical rotatory dispersion (ORD), circular dichroism (CD), and X-ray analysis are the most important. Sections III-B-1 to III-B-5 outline applications of these techniques for establishing the chirality around the sulfur atom. 

The oxidative conversion of the (-)-(5 )-A-tosyl methyl-p-tolyl-sulfimide 91 to the corresponding (-)-(/ )-sulfoximide 151 is of considerable interest because the absolute configurations of the substrate and product were established by the quasi-racemate method and by X-ray analysis (98), respectively. Therefore, the stereochemical result of this experiment indicates unequivocally that oxidation of chiral tricoordinate sulfur compounds proceeds with retention of configuration. 

Chemical preparation of the various sulfur compounds for isotopic analysis have been discussed by Rafter (1957), Robinson and Kusakabe (1975) among others. The gas generally used for mass-spectrometric measurement is SO2, although Puchelt et al. (1971) and Rees (1978) describe a method using SFs which has some distinct advantages it has no mass spectrometer memory effect and because fluorine is monoisotopic, no corrections of the raw data of measured isotope ratios are necessary. Comparison of 5 " S-values obtained using the conventional SO2 and the laser SFe technique has raised serious questions about the reliability of the SO2... 

The polarographic and potentiometric methods are not HPLC-run. The polarographic method relies upon the measurement of half-wave potentials of various sulfur compounds reacting with a mercury electrode. It is sensitive to submicromolar concentrations (Luther, pers. com.). While sulfide, thiosulfate, polysulfide and polythionates can be measured, the initial sample must be subdivided and pretreated in different ways. The disadvantages are that sample preparation ana analysis are time-consuming and there is no way to preserve samples for later analysis nor to study organic thiols with precision., ... 

The OPA method is based on the formation of a highly fluorescent isoindole derivative by reaction with o-phthalaldehyde and 2-aminoethanol in mildly basic aqueous solution (331. The advantage of this technique is that a large variety of thiols and other reduced sulfur compounds can be detected at subnanomolar to nanomolar concentrations. Its disadvantage is that the fluorescent derivative, which preserves the thiol in its reduced stage, is unstable and must be formed just prior to injection. These characteristics preclude the delayed analysis (e.g., in the laboratoiy) of large numbers of samples collected in the field. 

GLC-FID/FPD and GC-MS Analysis of Oxidation Products. To obtain information regarding the molecular structure of the organic sulfur compounds present in samples, each of the soluble oxidation products were methylated using the diazomethane method and then analysed, initially by both dual FID/FPD gas chromatography, and by GC-MS. Representative FID and FPD traces obtained from the Herrin No. 6 samples are shown in Figures 2 and 3 respectively, while those for the Indiana No.5 samples are shown in Figures 4 and 5 respectively. 

The determination of sulfur compounds in the range of concentrations, which occur in edible oils, is difficult. The literature on concentrations found in rapeseed and canola oils can be confusing. Considering relevance to hydrogenation effects and speed of analysis, ICP spectroscopy for determining sulfur in canola oil is presently the most appropriate method. 

Jordan,J. Stahl, J. Yakupkovic, J. E. "Instrumental methods of analysis of sulfur compounds in synfuel process streams". DOE/PC/40783-T9 and DOE/PC/40783-T10, NTIS, U.S. Department of Energy, 1983. 

Identified in roasted coffee by Sullivan et al. (1959), Heins et al. (1966), and Stoffelsma et al. (1968). Merritt et al. (1970) characterized it in roasted but not in green coffee. It is present in the headspace of roasted coffee (Cros et al., 1980 Wang et al., 1983 ), in the headspace of a brew (Shimoda and Shibamoto, 1990a) where it represents 0.67% (GC). Silwar et al. (1986) found concentrations of 0.01 ppm in arabicas and 0.10-0.12 in robustas after simultaneous distillation/extraction, capillary GC using simultaneously flame ionization or flame photometric (for sulfur-selective analysis) detectors (FID/ FPD). With a similar detection method in the GC analysis of the headspace compounds, Guyot and Vincent (1990) found 0.04-0.05 ppm in a roasted healthy arabica and 0.3-0.4 in the stinking quality (see Q.4). Procida et al. (1997) identified dimethyl disulfide in a roasted arabica but in none of the green coffees examined, contrary to their result for dimethyl sulfide (Q.ll). 

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