LCGC The Peak - April 2008 - (Page 19)

APRIL 2008 THE PEAK 19 the injection port liner, splatters, and then vaporizes. This nonhomogenous volatilization causes the less-volatile components to be swept out the split vent increasing discrimination. Better response was achieved in Figure 1b because of the deactivated glass wool near the top of the liner. Aside from forming a barrier to stop any solid particulates from getting onto the column, the glass wool has another important function: it provides additional surface area for volatilization. This feature improves vaporization for the lessvolatile compounds, giving a more consistent response for all analytes. Both of the liners used in the experiment had a single-taper gooseneck at the bottom of the liner. One reason for the taper was to help focus the sample onto the column and reduce interaction with the base of the injection port. This extends the life of the gold seal and decreases inlet activity. However, the taper does not stop inlet discrimination, as volatilization of the high-boiling compounds remains in close proximity to the split vent. Consequently, peak area and the signal-to-noise ratio are affected. The chromatogram in Figure 1b shows an overall increase in response with the liner containing glass wool for all retention times. However, as expected, the response of the latereluted compounds improved even more considerably. This is because later eluted compounds are less volatile and they are more impacted by inlet discrimination. The earlier-eluted compounds also showed an increase in response, but the increase in response was not as dramatic. This is because earlier-eluted compounds are low-boiling and do not require glass wool to volatilize. Therefore, it can be concluded that using a liner containing glass wool yields better results for samples containing a wide range of boiling points. Conclusion Injecting semivolatile compounds with a split flow leads to inlet discrimination. As demonstrated, the negative effects from inlet discrimination can be reduced greatly by switching from a standard gooseneck liner to a gooseneck liner containing glass wool. The liner containing glass wool stops solid particulates from entering the column and forces all semivolatile compounds to volatilize early in the inlet. Thus, the gooseneck liner with glass wool is a more reliable choice for analysis of semivolatile compounds.

Table of Contents Feed for the Digital Edition of LCGC The Peak - April 2008

LCGC The Peak - April 2008 Contents LC3LC: Comprehensive Two-Dimensional Liquid Chromatography Split Injections in Gas Chromatography: How to Reduce Inlet Discrimination A Simple and Solvent-Free Method for Determining Tetracyclines in Prawns Industry News Events Education

LCGC The Peak - April 2008

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