More GC Inlet Observations for Endrin and DDT Degradation

OK, by now you’ve probably noticed that I’m obsessing on Endrin and DDT degradation for splitless injection when doing EPA Method 8081b for organochlorine pesticide analysis.  As noted in the previous blog titled "A Fast Autosampler Injection Can Promote DDT Degradation", a fast autosampler injection into a GC inlet liner that does not have glass wool packing can exacerbate DDT degradation by throwing the liquid sample directly to the hot metal bottom seal.  For the experiment in this blog, I used a stainless steel inlet seal in my Agilent 6890 GC splitless inlet, something you’d never do on purpose unless you’re daft (I’ve always wanted to use that Old English word...), instead relying on gold dual vespel ring inlet seals or Siltek dual vespel ring inlet seals for their inertness and ease-of-use.  But I wanted to prove unequivocally that DDT on a hot piece of metal is a bad, bad thing, so I coupled the stainless steel seal deal with a 4mm open liner (no bottom taper) and the fast autosampler injection.  Check it out: the figure shows DDT degradation (to DDE and DDD) for that open liner at almost 30%, dropping by about half when a slow injection was used.  Employing a single taper liner with no wool, while not ideal, got the DDT degradation down even further, especially when a slow injection was used.  Endrin is relatively unflappable under these conditions, illustrating that its breakdown mechanism is different.