Accurate Analysis of Low-Level Sulfur Compounds Using Gas Chromatography Coupled with a Sulfur Chemiluminescence Detector

Ken Brady, Agilent Technologies (NL)

Being able to measure sulfur compounds reliably and routinely is of utmost importance to the petrochemical industry.  For liquid petroleum analysis, sulfur-containing compounds are present in petroleum feed stocks and are monitored during the refinement process in order to effectively maintain downstream processing.  In natural and petroleum gases, sulfur may be naturally occurring or added for safety purposes.
A gas chromatograph equipped with a sulfur chemiluminescence detector (SCD) provides rapid and efficient means for quantifying sulfur compounds from various processes.  SCDs provides linear responses to sulfur-containing compounds with improved detector stability and minimal hydrocarbon interference.
For this experiment the detector was combined with an Agilent 9000 Intuvo gas chromatograph (GC) which provides a smaller footprint, inert flow path, direct heating technology, and click-and-run connections.  The inert flow path allowed for repeatable and quantitative transfer for 22 sulfur containing compounds from ranging from 100ppm to 0.1ppm.  For light petroleum liquids, the average area repeatability was found to be 4.1% for the 0.1ppm standard (0.01 ppm on-column due to a 10:1 split) and improved to 3.2% or better for the higher concentrations.  The coefficient of determination was found to be 0.999 for >80% of the analytes evaluated.
The practical limit of detection for this application was determined by injecting a 20ppb standard split 10:1. A majority of the 22 analytes were differentiated from baseline noise at this level indicating a practical limit of detection of 2ppb.  Analysis of natural gas samples on an Intuvo GC equipped with a gas sampling valve will also be presented.  The click-and-run connections on the GC improves the user experience and simplifies method development by enabling quick column changes.  This highly stable system with an innovative inert flow path that greatly simplifies and improves the analysis of sulfur-containing compounds.


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