Sulfur and halogens (fluorine, bromine, and chlorine) are not only commonly analyzed in petrochemical products, they are often measured in polymers, coal-based chemicals, construction materials, and pharmaceutical intermediates as well. Contamination of these trace elements can either cause corrosion (halogens), decrease the catalyst’s lifetime (sulfur), or pollute the environment (sulfur). Therefore, analysis of these trace elements must be performed for different oil and gas products at different stages of production to guarantee their high quality.
Because of the organic sample matrix, sulfur and halogen analysis in oil and gas is difficult to perform using conventional ion chromatography (IC). However, combustion ion chromatography provides efficient and reliable results.
In combustion IC, samples undergo combustion digestion (pyrolysis) in an oxidizing atmosphere, and the resultant vapors are trapped in a solution. The liquid samples are directly loaded on an ion chromatography system for analysis. Under oxidizing conditions at high temperature, the halogens are converted to volatile HX and X2 and the sulfur to SOx. Further in the absorbing solution, HX and X2 are converted to X- and SOx to SO42- for direct analysis on the IC system.
Sample preparation (combustion) can be conducted manually, but the process is tedious, and hazardous for the operator to transfer samples. The best solution is to use an automated combustion system where no manual sample transfer is needed. Automated combustion ion chromatography provides an easy, convenient solution for reproducible and accurate results.
Combustion ion chromatography introduces a much smaller amount of sample gases into a relatively larger volume of water, resulting in low concentrations of analytes at injection. In addition, for sulfate analysis, addition of hydrogen peroxide is necessary to oxidize different sulfur species to sulfate. However, peroxide may interfere with the fluoride peak.
Several solutions are available to overcome these problems:
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