A comparison of septum degradation data obtained from a variety of standard GC septa, including the Thermogreen™ LB-2, AG3 (Green), Thermolite ®, BTO ® and the Merlin Microseal™ were evaluated. This study was conducted to determine analytical system lifetime between inlet maintenance based on chromatographic performance of reactive compounds as a function of septum aging through repeated injections. It is widely accepted that gas chromatographic septa degrade relative to the operating temperature of the injector and also based on the physical interaction with the syringe needle. This interaction may cause shedding of particles which then accumulate in the injection port liner, or possibly on the GC column in rare cases. This will likely lead to reactive compound breakdown in the injection port of flash-vaporizing inlets and thus reduce the amount of time that an instrument may be operated between inlet maintenance. Evaluations of the septa were based on the performance of the organochlorine compounds, endrin and 4,4'-DDT. These two compounds act as general indicators for the overall inertness of the GC injector, and their performance may be used to extrapolate to the performance of many other compounds. The average lifetime in terms of the number of injections for the studied septa was determined to range from 151 injections to nearly 2000 injections, depending on the septum. These values were found to be repeatable within the same septa material, or within class. The injection lifetime was found to be statistically different between different septa, however, indicating that not all septa are equivalent in terms of their durability to repeated injections. Additionally, some septa were found to predominately cause degradation of endrin, while others were found to cause reactivity of 4,4'-DDT, indicating that a difference in septa material may cause differences in what types of compounds become reactive in the GC inlet.
All Science Journal Classification (ASJC) codes
- Analytical Chemistry
- Organic Chemistry