Oxidative microcoulometry

Oxidative microcoulometry has become a widely accepted technique for the determination of low concentrations of sulfur in petroleum and petroleum products (ASTM D3120). The method involves combustion of the sample in an oxygen-rich atmosphere followed by microcoulometric generation of a triiodide ion to consume the resulting sulfur dioxide. It is intended to distinguish the technique from reductive microcoulometry, which converts sulfur in the sample to hydrogen sulflde that is titrated with coulometrically generated silver ion. 

Trace Quantities of Sulfur in Light Liquid Petroleum Hydrocarbons by Oxidative Microcoulometry... 

SULFUR (by Oxidative Microcoulometry) (Based on ASTM D3120)... 

Raney Nickel Reduction Apparatus in Appendix IIIC under Sulfur by Oxidative Microcoulometry). On top of the boiling flask, fit a water-jacketed distillation column with hooks. To the distillation column, fit a piece of glass tubing with ground ST inner joints with hooks, and connect the distillation column and a gas dispersion tube with ST outer joints with hooks. 

Hydrocarbon impurities in propylene can be determined by gas chromatographic methods (ASTM D-2712, ASTM D-2163), and another test is available for determination of traces of methanol in propylene (ASTM Test Method D4864). A gas chromatographic method (ASTM D-5303) is available for the determination of trace amounts of carbonyl sulfide in propylene with a flame photometric detector. Also, sulfur in petroleum gas can be determined by oxidative microcoulometry (ASTM D-3246). 

There are about 20 laboratory based ASTM standard test methods available for the determination of sulfur in various petroleum products and lubricant samples [6]. These utilize diverse analytical techniques and have applicability range sparming from m% to low mg/kg levels. However, at the very low end of sulfur analysis there are only three or four test methods which can adequately determine sulfur in such fuels. These lab-based standard test methods include ASTM D 2622 - wavelength dispersive X-ray fluorescence, D 3120 - oxidative microcoulometry, D 5453 - combustion UV-fluorescence, and D 6920 - oxidative combustion electrochemical detection methods. Without a doubt, the most widely used two methods out of these in oil industry laboratories are D 2622 and D 5453. Studies have shown that at truly ultra-low levels of sulfur only D 5453 can deliver accurate and precise results. This conclusion has... 

Oxidative microcoulometry is used to determine trace quantities of sulphur in aromatic hydrocarbons. An oxidative pyrolysis converts sulfur to sulfur dioxide which is titrated in titration cell with the triiodide ion present in the electrolyte. 

ASTM D 3961-98. Standard test method for trace quantities of suUur in hquid aromatic hydrocarbons by oxidative microcoulometry. 

D3605, Trace metals in fuels by AAS D3961, Sulfur in aromatics by oxidative microcoulometry X X X ... 

ASTM D 2031-97. Standard test method for reducing substances in refined pyridine. Withdrawn 2003. ASTM D 3961-98. Standard test method for trace quantities of sulfur in liquid aromatic hydrocarbons by oxidative microcoulometry. Withdrawn 2004. 

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