Day 15 - GC-ECD investigations

I arrived at CERES at 8AM and left at 3:30PM. Anna left around 11:30AM to defend her masters thesis; Woooohoooo Anna!!!!!

Anna and I investigated the portion of the instrument where the capillary columns connect to the make-up gas adapter today. Upon unscrewing the Swagelok nuts that fasten the make-up gas adapter/capillary columns to the detectors we found that both front and back detector 1/4" graphite vespel ferrules were in extremely poor condition; actually they crumbled apart inside the nut. Additionally, we found that both nuts were loose. However, both fused silica liners were in good working shape and were not replaced.

Columns were then re-installed, all other connections inside the GC oven were tightened, and then we purged the system with carrier and make-up gases for 15 minutes to remove oxygen. Anna and I then began to equilibrate the system with the GC-oven at 30C in case thier were air leaks. After 4 hours, the baselines stabilized (Front at 880 +/- 1Hz, Back at 2630 +/ 2.5 Hz), I loaded the GC-oven operating temperature for our analytical method, and that steady consistent baseline we had just obtained began to wander across the real-time display like the Mississippi river, similar to what was seen last Friday. At this point, I figured that the only variables still in my control that I had not tampered with were the columns. So I ramped up the GC oven to 310C and let is cook for 20 minutes. See below and notice the scale on the y-axis for the back detector, the front column was ~3-4 times lower than this:

Front Detector

 Back Detector

Once the big nasty stuff had abated, I dropped the GC-oven down to operating temperature - 110C and let it sit. This is what was found:

Front Detector

Back Detector

By 3:45 PM, detector background readings were continuing to plummet with no sign of stopping anytime in the near future. I concluded that it would take several hours for the system to re-equlibrate and decided to let it work towards this end until morning. I'll report back tomorrow.