Day 8 - Friday

We arrived at the CERES laboratory at 8AM and left at 4:30PM.

At the GC-ECD instrument - Single component pesticide solutions run last night were used to identify 17ms and XLB peaks today. Adama and Marie received training on how to use Chemstation to identify analytes. Each independently identified 4 compounds by comparing calibration standard to single component solution chromatograms. In all, ~ 35% of the project analyte list was run as singles. This information was used to update calibration table retention times for the 17ms; the XLB portion of the cal table will be updated on Monday. PRC compounds were identified through comparison of CERES chromatograms to OSU generated chromatograms. This is the best we can do because we do not have singles of these compounds at CERES. Interestingly, chromatograms of standards generated at CERES display many more peaks than the OSU generated chromatograms. In fact some of the “extra peaks” match the retention times of impurities in in Ted's 2011 single component solutions. Could these “extra peaks” in cal standards be related to the long transport time and high ambient temperature experienced during shipment from OSU to CERES? It’s plausible.

  

In the sample preparation lab – the CERES team continued with PSD extractions and completed a third batch. I worked with Marie to improve her sample preparation technique; specifically I demonstrated how to hold extraction jars when decanting extracts into round bottom flasks so as to minimize contamination and spills. Another batch of glassware has been prepared for bake out over the weekend. Anna and I plan on meeting on Sunday to initiate the extraction of a 4^th batch of PSDs so that come Monday, the lab can continue extracting. CERES staff continue to fill out benchsheets thoroughly and completely. When not working on our project, staff continued to work on validating a QuEChERS method for the analysis of pesticides in agricultural products.

I’m still working out how exactly to proceed with sample analysis considering the limitations of the back detector (i.e. how it slams the internal standard signal through the top of the detector).       

Day 7

Anna, Marie, Adama, and I were at the lab from 7:45AM to 6:30PM today.

I was on the GC-ECD instrument most of the day. I've concluded that the large peak that shows up in the chromatograms and maxes out the back detector is indeed the internal standard; it is present at the same magnitude in both calibration sets at all levels, it has the same Rt as the single component IS solution, and it's amplitude relative to the rest of the peaks present in the chromatograms is similar to what was seem when we ran these standards at OSU. Again, it appears to be a detector related issue where instrument response increases non-linearly with increasing instrument background.

Anna and the CERES staff completed the sample preparation of the second batch of PSDs. Included in this batch was a native over-spike that was introduced at the rotary evaporation step of the the sample preparation process. This will provide information on compounds specific losses that could be occurring at this step - a step that is conducted using lab apparatus that deviates from OSU's. The concentration of natives in the final extract should be ~100ppb. I will have them prepare one more of these today so that we have n = 2. I will also have them include extraction surrogates (TCMX and decachlorobiphenyl) with this replicate.

I racked up a sequence of singles to run on the GC-ECD through the evening; mainly compounds that have poor resolution with other compounds and key quality control residues. Additionally, the third batch of PSD dialysis was initiated and another batch of glassware is baking out.

Specific points:

1. CERES ran out of n-hexane today at the rotary evaporation step of sample processing. However, the vendor finally showed up ~1 hr later with the delivery of n-hexane. Supposedly Ann has been asking them for this shipment since before I arrived. We were also informed that this was the last batch of n-hexane in Senegal for unknown amount of time... they would not give me a straight answer. Is this the only vendor in Senegal? Anyways, doing a back of the envelope estimate, it appears that CERES has enough n-hexane to complete the preparation of PSDs.
2. Dakar power went out today for over an hour and the generator was turned off due to some undisclosed system failure. At this point, all instruments were cycled off and extractions were delayed until the power came back on and the generator had been evaluated by CERES' generator contractor. 
3. CERES staff are continuing to become more comfortable in the lab. I have instructed them to perform dialysis with 2 people so that 3rd person could take a rest (the average temperature of the prep lab during this part of the year is 30 C - 86 F and the fume hoods perform poorly).
4. CERES staff have continued filling out paperwork thoroughly by making it a top priority.        
5. Analysis of calibration standards revealed that there are more peaks in the chromatograms than expected; some are quite significant. Additionally, the peaks are present in both calibration sets and to the same degree. Running the singles will help with compound ID.

Day 6 - A wave of visitors

Anna and I arrived at CERES at 7:50AM and left at 5:30PM.

CERES picked up on the second dialysis of the first batch of PSDs today. They started off a little bit shaky, but then fell into a groove by the 3rd sample; better oral communication helped. True to their word, CERES was able to complete the rotary evaporation of 8 samples in about 2.5 hours. As of this evening, sample preparation of the first batch of PSDs has been completed, extraction of the second batch was initiated, and all glassware needed for tomorrow is baking overnight.

Around 10 AM, CERES received an unexpected visit from their GC-ECD maintenance contractor that lasted for roughly 2 hours. They performed an experiment where they reversed the columns, made a couple of observations, and confirmed that the back detector is in need of  some heavy maintenance or replacement. However, I did not receive any indication of what they would do next or at what time they would be back. I then re-installed the columns as per our SOP (~45 min), equilibrated the instrument (~1hr), shot an instrument blank (~ 1hr) and the 100ppb cal standard (~ 1 hr). I will inject single component solutions of the internal standard  and other pesticides that need to be Rt verified tomorrow. 

Specific Points:

1. As observed by other OSU staff, CERES fume hoods are not very effective at clearing solvent vapor from the lab. Additionally, they only have two positions... opened and closed.
2. CERES stored post-deployment cleaned PSDs in what appears to be 200 mL amber glass jars; a level that nearly overflows with 200 mL of extract. I instructed them to extract PSDs into 180 uL of solvent. PSDs are fully submerged at this level.
3. CERES does not have a large wide funnel, only a medium sized one. CERES would minimize small spills and increase their processing speed through the purchase and use of a larger glass funnel.
4. CERES has been filling out benchsheets with much more rigor, attention to detail, and care. 
5. Hama and Makhfousse stopped by the lab and talked with CERES staff at length about the importance of filling out benchsheets completely and accurately, describing sampling locations using cardinal directions, and sample traceability. This lasted roughly 1 hr.   
6. Several other non-project affiliated people stopped by the lab to talk with CERES staff. Anna was mainly in charge of speaking with these folks.

     

Day 5 - And we're off!

I arrived at 9 AM and left at 5:30 PM; it was a full day in the CERES lab for Anna, Adama, and me.

Major points of the day:

1. Air Liquide finally got back to Anna. Helium and nitrogen purities are both 99.995%.
2. Laboratory reagent blanks analyzed over the weekend displayed a few small peaks that will likely fall below our calibration curve and a few larger peaks that would probably quantitate, but don't line up with standard Rts or are absent on the second column.  
3. A leak was found in the nitrogen line prior to the in-line O2, Air... filter. It took some time, mainly due to locating tools, but the leak is no more. However, I cannot attest to the state of the filter and CERES does not have a spare on hand.
4. It was found that the 1/4'' Swagelock nut on the makeup gas adapter was loose on both the front and back detectors. Both were tightened, but I'm not sure how long they have been this way. After bringing the system back up and allowing time to equilibrate, I observed the lowest instrument background yet; the front detector came down by 35% while back detector came down by just over 20%. Instrument blanks are running over night.
5.  CERES staff insisted that one of their small pumps could not be hooked up to two roto-vaps. However, they felt confident they could do batches of 8/day using only two roto-vaps; a rate comparable to OSU. We will see how tomorrow goes.
6. CERES staff reviewed necessary SOPs and were instructed to watch OSU's LFT extraction training video this evening. 
7. Dialysis on the first batch of field deployed PSDs was started. The batch includes trip, field and an extraction blank.Surrogates were added to all samples. CERES staff are filling out benchsheets thoroughly.
8. All materials needed to complete the first extraction batch are in the oven tonight at 325 C and will be ready by morning.

The plan for tomorrow is to oversee the remainder of the first PSD extraction batch, evaluate instrument blanks, inject a call standard, shoot a handful of singles, set-up for the next batch of PSD dialysis, potentially set the calibration to run through the evening.   

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.