SULFUR DETERMINATION BY OXIDATIVE MICROCOULOMETRY: D3246
(Equivalent Test Methods: IP 373 and AFNOR M07-052)
This test method is valid in the sulfur concentration range of 1.5 to 100 ppm in hydrocarbon products that are gaseous at normal room temperature and pressure. This test method is applicable in the presence of total halide concentration of up to 10 times the sulfur level and total nitrogen content of up to 1.0 %. Free nitrogen does not interfere. This test method is not applicable in the presence of total heavy metal concentration (for example, nickel, vandium, iron, lead, etc.) in excess of 500 ppm. Stringent techniques should be employed and all possible sources of sulfur contamination must be eliminated to achieve the quantitative detectability that this test method is capable of.
TEST SUMMARY
A liquid sample is injected into a combustion tube maintained at about 800° C in a flowing stream of gas mixture of 80 % oxygen and 20 % inert gas such as nitrogen or argon, etc. Oxidative pyrolysis converts the sulfur to sulfur dioxide, which then flows into a tiration cell where it reacts with triiodide ion present in the electrolyte. The triiodide thus consumed is coulometrically replaced and the total current required to replace it is a measure of the sulfur present in the injected sample.
TEST PRECISION
In the 0 to 10 mg/kg level of sulfur, the test repeatability is 0.4 and reproducibility is 5 mg/kg.
The bias of this test method has not been determined.
