Mark Wainwright Analytical Centre Unsw

MARK WAINWRIGHT ANALYTICAL CENTRE UNSW

XRF FACILITY

METHODOLOGY:

Sulphur Analysis:

Approximately 0.1000 grams of powdered sample material is weighed into a ceramic boat, and the weight recorded. The appropriate calibration program is selected and the boat placed onto the loading assembly. Weights can be varied depending on the program and the amount of sulphur within the sample. The analysis is performed as described below.

Theory of Operation:

“ Sulfur determination with the TruSpec Add-On Module is completely independent of the carbon, hydrogen and nitrogen determination. Analysis begins by weighing out a sample…into a combustion boat. The sample is placed in the combustion system, which is typically regulated at 1350 oC with a pure oxygen environment. The combination of furnace temperature and analyze flow cause the sample to combust.

All sample materials contained in the combustion boat go through an oxidative reduction process that causes sulfur-bearing compounds to break down and free the sulfur. The sulfur then oxidizes to form

SO2. The design of the combustion system prevents atmosphere from entering the sample combustion zone. After a preset time, oxygen begins to flow through the lance to accelerate the combustion of hard- to-combust materials, and the sulfur (as SO2) is released into the carrier flow as sample gases. Sample gases are first swept through the boat stop to the back of the inner combustion tube, then forward between the inner and outer combustion tubes, allowing the sample gases to remain in the high temperature zone for a longer period for more efficient oxidation.

From the combustion system, the gases flow through the Anhydrone tube to remove moisture, through a flow controller, which sets the flow of sample gases to 2.5 lpm, then through the infrared detection cell... The cell measures the concentration of sulfur dioxide gas present. The instrument converts that value using an equation preset in the software, which takes into account the sample weight, calibration, and known moisture value. Answers are reported as percentage/ppm or grams.” (LECO 2007: 7-3)

Instrumentation:

LECO TruSpec Add-on Sulfur Module

Reference:

LECO, 2007, TruSpec Add-On Module: Instruction Manual. St. Joseph, Michigan: LECO Corporation.