Author: Jack Cochran
Published By: LCGC Chromatography Online
Issue: Volume 12, Issue 16
Year of Publication: 2016
Hopefully, by now at least, readers who are following this Practical GC series on split injection gas chromatography (GC) (1–3) have been able to take advantage of its benefits in their own laboratories. Chemists analyzing environmental samples, especially those that produce dirty extracts, could have the most to gain from split injection GC given the wide variety of semivolatile organic compounds that are typically determined. Analyte lists include compounds that can react with GC inlet liner surfaces during splitless injection, leading to degradation of those compounds, which prohibits their accurate quantification. In fact, an example was given in my first Practical GC article in The Column (1) for the pesticides endrin and DDT. Sample extracts containing high concentrations of involatile material exacerbate the situation because the nonvolatiles are deposited on the inlet liner wool and bottom seal where they catalyze degradation of sensitive compounds. Buildup of nonvolatile material in the inlet during repeated splitless injections leads to even higher breakdown. Split injection mitigates the degradation potential because the typical inlet flow is 10 times (or more) higher than for splitless injection. The time for unwanted reactions on liner surfaces, including those that have been modified by nonvolatile coextractives, is reduced in split injection.