Good and bad news...today we re-looked at the chromatograms and realized there was a switch that must have happened between the reagent blank and a real sample during a transfer step during processing. This was confirmed through our duplicate analysis. The reagent blank looks exactly like the sample "field site #3 duplicate". We can never know for sure but the chromatograms are fairly undeniable. We still don't know where the other contamination came from in the other QC samples (which is the bad news). Tomorrow when we run our 2nd retrieval samples we will have a better idea. If I don't find out what caused it by the time I leave the staff here are very motivated in finding where it came from....they want to succeed. Anna has picked up fairly fast on the GC training I'm happy to say. I will post if and when we find out what might have happened...or any other interesting revelations.
Here are the internal dimensions of the oven shown as actual(usable): DxWxH 55cm(53), 33cm(29, shelf braces), 31cm(31). We can fit a maximum of 7 cages inside (more practically 6). I do not think it is possible to put an exhaust fan or a port on it, it is the wrong type of oven for that. If there are any more questions about the oven feel free to ask.
Today we re-updated the calibration table for the front and back detector (Anna and I, Marie, Adama, and Vieux were present too). We keep running into problems with some compounds continually shifting retention times (propanil, dimethoate, fipronil). We ran in to some other problems with the back column. I think we may need to invest in some backup and/or new columns. I don't think the back column is in all that good of shape as near as I can tell. We vialed up some new standards and are running those tonight.
Tomorrow we will run the 2nd retrieval samples on the GC and start working on the calculation spreadsheet.
We did a dialysis on the blank LFT we put out into the lab. I'm not sure if we can run these on the GC before I leave though. If I don't I am confident the staff can.
Tuesday, March 3, 2009
Week 6 - Monday
The 1st retrieval samples ran over the weekend on the GC.
GC training was done with Anna mostly (Adama, Marie, and Vieux were watching, but were also in and out). We processed the front column chromatograms and looked at the standards we ran with the samples. While viewing and processing the QC samples it was obvious that there was a cross contamination (of most of the analytes in our method) issue happening, which is unfortunate. The worst sample was probably the reagent blank, which during the dialysis was the last sample to be transferred and processed to see if we had cross contamination.
Part of the day was spent trying to track down where this contamination occurred. There was a centrifuge tube that had hexanes in it that was in the blow down module that had been exposed to the air in the lab for ~1 week and we ran that and found no peaks that were identifiable, so the contamination is probably not coming from the ambient air. I had previously not seen any contamination with solvent blown down on the rotovap, so that is likely not the source.
We made 4 blank LFT and set them up in the hood, bench top, freezer, and LFT construction rig to see a worse case scenario. If we see nothing in these samples then I don't really know where the contamination came from. If you have any ideas please post them as a comment to this post.
Tuesday I hope to prepare and run samples from the 2nd retrieval. We will also finish updating the the calibration curve for the back column and hopefully finish analyzing chromatograms so we can start looking at the calculation spreadsheet.
GC training was done with Anna mostly (Adama, Marie, and Vieux were watching, but were also in and out). We processed the front column chromatograms and looked at the standards we ran with the samples. While viewing and processing the QC samples it was obvious that there was a cross contamination (of most of the analytes in our method) issue happening, which is unfortunate. The worst sample was probably the reagent blank, which during the dialysis was the last sample to be transferred and processed to see if we had cross contamination.
Part of the day was spent trying to track down where this contamination occurred. There was a centrifuge tube that had hexanes in it that was in the blow down module that had been exposed to the air in the lab for ~1 week and we ran that and found no peaks that were identifiable, so the contamination is probably not coming from the ambient air. I had previously not seen any contamination with solvent blown down on the rotovap, so that is likely not the source.
We made 4 blank LFT and set them up in the hood, bench top, freezer, and LFT construction rig to see a worse case scenario. If we see nothing in these samples then I don't really know where the contamination came from. If you have any ideas please post them as a comment to this post.
Tuesday I hope to prepare and run samples from the 2nd retrieval. We will also finish updating the the calibration curve for the back column and hopefully finish analyzing chromatograms so we can start looking at the calculation spreadsheet.
Week 5 - Saturday
We have a lot of work to do still, especially on the GC and thus we Anna, Adama, and I came in to work from 9 to 3:30.
Anna, Adama, and I spent most of the day updating the calibration table and doing training on the GC. We also now have all compound retention times in the calibration table correctly. While updating, it was clear that a few compounds don't show up on the GC here as well as they do at OSU, especially fipronil, dimethoate, and propanil. These compounds may need to be dropped from the method. A lot of time was lost today because of a software glitch with Chemstation. The calibration table would not communicate correctly with it's own software and had to be rebuilt a few times. It was good practice for the staff, but a set back nonetheless.
We prepared the 1st retrieval samples to be run on the GC over Saturday night and Sunday. Adama brought the samples up to volume, I transferred them to the GC vials at 1 mL, and Anna administered the I.S. spike. One sample was compromised as a result of a bad spike, but the samples were analyzed in duplicate.
Anna, Adama, and I spent most of the day updating the calibration table and doing training on the GC. We also now have all compound retention times in the calibration table correctly. While updating, it was clear that a few compounds don't show up on the GC here as well as they do at OSU, especially fipronil, dimethoate, and propanil. These compounds may need to be dropped from the method. A lot of time was lost today because of a software glitch with Chemstation. The calibration table would not communicate correctly with it's own software and had to be rebuilt a few times. It was good practice for the staff, but a set back nonetheless.
We prepared the 1st retrieval samples to be run on the GC over Saturday night and Sunday. Adama brought the samples up to volume, I transferred them to the GC vials at 1 mL, and Anna administered the I.S. spike. One sample was compromised as a result of a bad spike, but the samples were analyzed in duplicate.
Week 5 - Friday
The results from the GC run overnight shows that there is little difference between using centrifuge tubes marked at 1 and 2 ml and using an automated pipet for 1 mL. The key is being accurate with the marks on the centrifuge tubes. Given this information we prepared standards for the calibration table with internal standards (Adama pipeting each composite standard dilution and me introducing the internal standard). These ran over night.
We also performed a dialysis of the 2nd retrieval samples and some of the QC. I will be taking some QC samples (1 trip blank, 1 field exposure blank, 1 lab cleaning blank) back with me to OSU. I observed the dialysis and corrected technique where needed but for the most part did not physically help. The staff's technique had improved since the 1st retrieval's samples were processed. (Adama, Anna, Vieux, and Marie were present)
We also performed a dialysis of the 2nd retrieval samples and some of the QC. I will be taking some QC samples (1 trip blank, 1 field exposure blank, 1 lab cleaning blank) back with me to OSU. I observed the dialysis and corrected technique where needed but for the most part did not physically help. The staff's technique had improved since the 1st retrieval's samples were processed. (Adama, Anna, Vieux, and Marie were present)