Dakar, Senegal experienced another heavy storm last night that continued through to this evening. I video recorded some thunder and lightning and saw many cars driving through water deep enough to slosh over car hoods. I was also feeling a bit fatigued today for some reason. I arrived at the lab at 7:45 AM and left at 5:30PM.
Anna and I worked on updating the GC-ECD calibration table for the majority of the day. This process was slowed by my unfamiliarity with this version of Chemstation - the instrument software. Additionally, I was frustrated to learn that manual integrations, a tool that I rely heavily on to ensure data quality, can not be saved in away that links them to calibration tables... they are literally snapshots in time. So Anna and I would go through a chromatogram, correct mis-integrations, immediately update the cal table with this information, save the updated method, and save "chromatographic windows" incapable of being re-processed. But at the very least they provide traceability for the analysis. On the bright side, creating the calibration table in this fashion did force Anna and I to do the best job we could integrating chromatograms the 1st time; the cost is too great to go back through that process.
Regardless of these challenges, we were able to successfully input all necessary data into the calibration table.We found that almost all compounds run on the FRONT column/detector met project data quality objectives producing r^2s greater than or equal to 0.99 and were composed of 4 or more levels. The only exception was captifol. The low sensitivity of this compound resulted in a 3 point cal curve from 100-1000ppb. All other pesticides generally calibrated in a range from 5 - 500ppb with a couple from 5-1000ppb.
For the BACK column/detector, I integrated the flat-topped internal standard peak, averaged it over all cal levels, and used this value to produce average response ratios for the purposes of a semi-quant analysis. All pesticides run on the back column produced r^2s greater than or equal to 0.99 and were composed generally of 4 levels ranging from 5-100ppb.
While Anna and I worked on the GC-ECD, Adama and Marie continued to chip away at PSD extractions. All said, they completed another BIG batch, washed and began baking all necessary glassware for tomorrow, and initiated the extraction of a 5th batch of PSDs. Tomorrow CERES will continue with PSD extractions, while Anna and I begin running samples.
No comments:
Post a Comment