Day 4 - Friday

Today was a short day in the lab ~ 5.5hrs as a result of the Ramadan holiday.

The DB-17ms and DB-XLB capillary columns installed yesterday were conditioned this morning until a flat baseline was achieved. This took roughly 3 hours. The front detector (17ms) baseline stabilized at 860Hz, back detector (XLB) was at 1580Hz. For reference, instrument baseline was < 50Hz in 2007, ~ 200Hz in 2009, and in 2011 it was reported by Ted Haigh that, "The detectors seem to be running right on the upper limit of being useful and no additional baking seems to make any difference. The ECD cells are probably getting toward the end of their lifespan in this environment. I would expect that they will perform adequately for at least another year or two before needing to be replaced." It appears to me that this trend has continued, which suggest routine instrument maintenance issues.   

While the columns were conditioning, Anna, Marie, Adama, and I discussed PSD extraction logistics. I informed them that OSU had recently demonstrated that the first PSD extraction could be set up over night, showed them the benchsheets where this was documented (thank you OSU staff), and they agreed that this was a good strategy to proceed with.

Once columns were conditioned, the new 100ppb calibration standard sent from OSU was injected. Chromatographic resolution and peak shape on the theDB-17ms were greatly improved compared to the DB-17, the same is true of the newly installed DB-XLB column. However, the internal standard peak exceeds the instruments capabilities on the back column. This makes calibrating the XLB/back detector really difficult. Considering the state of the instrument, I think that we can calibrate from 5 - 500ppb on the 17ms/front detector and use the back column strictly for Rt confirmation. This will be confirmed with Kim Anderson of OSU and communicated to CERES staff, along with the rationale, before proceeding. I have been doing this work mainly.

Before leaving for the day, a GC-ECD sequence was prepared to analyze laboratory reagent blanks over the weekend. I was also informed that CERES planned to use two rotoray evaporators for samples extraction. However, they have several of these apparatus. I will recommend that they set up two additional roto vaps in order to maintain an efficient sample prep workflow. I still have not heard back on the purity of our nitrogen tanks. Sample extraction is set to begin Tuesday as Monday is a holiday.

Specific points:

1. CERES staff are rusing while entering information into Chemstation, which has led to ~ 3 runs being restarted or fixed on the fly. CERES staff need to slow down and pay attention to details when using the Chemstation software.
2. CERES staff have had a little bit of trouble completing a few specific tasks, namely confirming compressed gas purities and ordering replacement nitrogen tanks. Could this be related to our higher than usual detector baseline? Whose to say, but it seems easy enough to rule out via a call to the vendor.
3. CERES staff did not seem to be aware that GC columns need to be installed with the appropriate sized ferrule. They were going to use 0.5 mm ferrules with a column that takes a 0.4mm. I made sure that the correct ferrule was used.