Sulfuric trace analysis

Iron, thickness measurement, 150-152 trace analysis by x-ray emission spectrography, 163, 225-232 Iron-55, as x-ray source for sulfur determination, 130, 133-135 Iron oxides, analysis, 182, 184 Irradiance, definition, 6 Irradiation, equipment for, 177 of polymers, 177... 

A disadvantage of supercritical fluids for extraction is that most common fluids used for extraction (carbon dioxide, nitrous oxide, sulfur hexafluoride, etc.) are weak solvents, limiting the polarity and molecular weight range of analytes that can be efficiently extracted. Also, for trace analysis the availability of fluids of adeguate ptirity may be a problem. 

Rauhut, D. (1990). Trace analysis of sulfurous off-flavours in wine caused by extremely volatile S-containing metabolites of pesticides e.g. Orthene. In Actualites Oenologiques 89, Comptes... 

Oostdijk, J.P., Degenhardt, C.E., Trap, H.C., Langenberg, J.P. (2007). Selective and sensitive trace analysis of sulfur mustard with thermal desorption and two-dimensional gas chromatography-mass spectrometry. J. Chromatogr. A. 1150(1-2) 62-9. 

In trace analysis of contaminant substances, one can use specific detectors for certain compounds, such as a nitrogen-phosphorus detector (NPD), thus gaining detection ability for nitrogenated and phosphorylated compounds the electron-capture detector (ECD) shows excellent performance for chlorinated substances and the flame photometric detector (FPD) is the most widely used for sulfur-containing compounds. 

Hall electrolytic conductivity detector An element-selective GC detector primarily intended for trace analysis of organic compounds containing chlorine, nitrogen, or sulfur. In operation, this detector pyrolyzes the column effluent gas into soluble electrolytes that are dissolved in a stream of deionized liquid. The observed change in electrical conductivity, proportional to the amount of material present, is measured. 

Finally, the typical anion chromatogram in Figure 10.153 exemplifies the trace analysis of sulfur dioxide it was obtained under standard conditions on lonPac AS4A after preconcentration of 5mL absorber solution. The sulfate peak... 

Figure 10.153 Trace analysis of sulfur dioxide, conductivity preconcentrated volume 5mL Separator column lonPac AS4A eluent concentrator column TAC-LP1 peaks 10 nL/L...

Fig. 9-92. Trace analysis of sulfur dioxide. - Separator column lonPac AS4A eluant 1.8 mmol/L NajCOj + 1.7 mmol/L NaHCOj flow rate 1 mL/min detection suppressed conductivity preconcentrated volume 5 mL concentrator column TAC-LPl peaks 10 nL/L sulfur dioxide (1) as sulfate.

The determination of molecular formulas via accurate mass measurements relies on isotopic masses accurate to at least 1 in 10 [10]. Elemental trace analysis is required for the detection of radioactive nuclides in the environment, of transition metals such as Pt in exhaust fumes from automobiles [11], and in the quality control of low-sulfur fuels for the same. All electronic devices demand for high-purity semiconductors and the properties of alloys are critically influenced by trace elements [12]. Age determinations from isotope ratios are applied in archeology, paleontology, and geology [4,13,14]. More recently, elemental MS and biomedical MS are jointly employed to unveil the presence and preferably location of metals in proteins or DNA as well as their lateral distribution in tissues [15-18], a field of research basically going back to seminal work by Houk in 1980... 

Limitations Adjustment of the combustion gases important for reproducibility and selectivity. In sulfur mode, quenching effect is possible because of too high hydrocarbon matrix (double flame necessary). Sensitivity in sulfur mode is not always sufficient for trace analysis. 

Development of test methods for process (on-line) analysis and validation of these analyses are continuing under the direction of ASTM Committee D02.0D, Section 1 and D02.25. A proposed gas chromatographic/selective detection method is under development for the trace analysis of sulfur com-pKnmds in ethene and propene. 

It is noteworthy, however, that traces of sulfur can have beneficial effects on the anti-wear resistance of fuel injection pumps. It is thus undesirable to reduce the sulfur content to extremely low values unless additives having lubricating qualities are added. Independently from total sulfur content, the presence of mercaptans that are particularly aggressive towards certain metal or synthetic parts is strictly controlled. The mercaptan content is thereby limited to 0.002% (20 ppm) maximum. The analysis is performed chemically in accordance to the NF M 07-022 or ASTM D 3227 procedures. 

Reference methods for criteria (19) and hazardous (20) poUutants estabHshed by the US EPA include sulfur dioxide [7446-09-5] by the West-Gaeke method carbon monoxide [630-08-0] by nondispersive infrared analysis ozone [10028-15-6] and nitrogen dioxide [10102-44-0] by chemiluminescence (qv) and hydrocarbons by gas chromatography coupled with flame-ionization detection. Gas chromatography coupled with a suitable detector can also be used to measure ambient concentrations of vinyl chloride monomer [75-01-4], halogenated hydrocarbons and aromatics, and polyacrylonitrile [25014-41-9] (21-22) (see Chromatography Trace and residue analysis). 

The analytical chemistry of titanium has been reviewed (179—181). Titanium ores can be dissolved by fusion with potassium pyrosulfate, followed by dissolution of the cooled melt in dilute sulfuric acid. For some ores, even if all of the titanium is dissolved, a small amount of residue may still remain. If a hiU analysis is required, the residue may be treated by moistening with sulfuric and hydrofluoric acids and evaporating, to remove siUca, and then fused in a sodium carbonate—borate mixture. Alternatively, fusion in sodium carbonate—borate mixture can be used for ores and a boiling mixture of concentrated sulfuric acid and ammonium sulfate for titanium dioxide pigments. For trace-element deterrninations, the preferred method is dissolution in a mixture of hydrofluoric and hydrochloric acids. 

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