Enhanced Pesticide Activity When Using Hydrogen as a Carrier Gas

During recent work using the Rtx-CLPesticides and Rtx-CLPesticides2 columns, I was exploring the use of both hydrogen and nitrogen as a carrier gas for analysis of EPA Method 8081 organochlorine pesticides and ran into a bit of a problem when I switched my system over to hydrogen from helium. Several components experienced a dramatic reduction in response, the worst of which were methoxychlor and 4,4’-DDT. Since the injector had not been maintenance in a while, and I had previously analyzed particularly dirty extracts, there was no surprise at the potential for activity, but it was shocking just how much became evident simply with the conversion to hydrogen. A simple liner replacement did not solve the problem, nor did a fresh inlet septum and gold inlet seal and although, the peak response improved with the installation of an additional liner, within a few injections the peak response was on the decline. I followed this with replacement of the injection syringe new guard and analytical columns and at Jack's suggestion, a Merlin Microseal (Using a Merlin MicroSeal Septum to Reduce Endrin and DDT Breakdown for EPA Method 8081b – Organochlorine Pesticides by Gas Chromatography) with the suspicion that metal debris deposited in the liner from the injection process was catalyzing a reaction of the more active pesticides with the hydrogen. The Merlin Microseal was instrumental in eliminating the deposit of both metal and septa particles into the liner and indeed, this seemed to fix the problem.