Today I injected the 500ppb calibration standard used during Ted's visit to Dakar inorder to get a sense of the state of CERES' GC-ECD. Chromatography on the DB-17 was tailing more than I'd like and several compounds were unresolved, mainly: chloroneb/trifluralin/INST/TCMX (Rt~19min), b-BHC/dimethoate/heptachlor (Rt~25-26min), and captafol/methoxychlor and mirex/endrin ketone (Rt~42min). This is likely due to column history and a lack of routine instrument maintenance. However, I was unable to evaluate DB-XLB chromatography because the majority of peaks in the 500ppb calibration standard maxed out the detector (i.e. >800,000 at 500ppb!). Unfortunately, this was not a major surprise due to the raised resting instrument baselines observed on Monday and Tuesday. But I was surprised that both detectors didn't max out, only the back detector. Hmmmm.
Regardless, laboratory reagent blanks, which were run on Tuesday, looked pretty good; two major peaks on the DB-17 which did not line up with peaks in the 500ppb cal chromotogram (good), and a few small rolling peaks on the DB-XLB which integrated to areas far smaller than our lowest cal standard.
At this point, I decided to inject Ted's100 ppb cal standard. All but one peak was within the DB-XLB detector's working range. This suggests that we could potentially get by using a 4 point linear calibration curve on the back column (5,10,50,100ppb), especially since OSU's analysis of the spilt samples revealed that just about all compounds were present at < 50 ppb. It also helps that the back column is used for confirmation and not quantitation.
Anna was finally able locate and put her hands on the OSU shipped care package; it only took 13 days! All materials were accounted for, however the standards were at ambient temperature and appeared to have been in this state for quite some time. Standards were immediately placed in the CERES refrigerator freezer.
I had Anna install the OSU shipped *DB-17ms* and DB-XLB. The newly installed columns were left to purge overnight and will be conditioned tomorrow morning.
My plan is to run the OSU shipped 100ppb calibration standard on the new columns tomorrow and make an evaluation for a way forward with the rest of the project. Anna and the rest of CERES staff have proposed beginning PSD extractions next Monday, after the culmination of Ramadan.
Anna has still not not heard back from Air Liquide on the purity of the N2 gas tanks which are to be employed in sample preparation and instrumental analysis.
