Last night Anna and I ran the I.S. and mix of PRC and 14 analytes so that we could update the calibration table retention times in Chemstation. At first glance the chromatograms looked great, but we are starting to lose a little resolution between some compounds...yet gaining some with others. The elution order and peak identification were hard to place a finger on with a few compounds near the middle of the run (Chlorpyrifos, Fipronil, PCB 100, Fenitrothion). The peak height ratios didn't really help much either. We found some standards in the freezer that had been previously used for other projects and did some dilutions and ran them for retention time. We are still sorting out two compounds. The back column was straight forward from the beginning. Also I am not seeing the breakdown in the inlet of compounds like I was before.
At the end of the day we realized that we were going to have a problem with pipeting 1 ml into or out of GC auto-sampler vials due to the pipet tip being too wide. After several email exchanges with Glenn and a Skype conversation with Paul we decided that we could just use the 1 and 2 ml graduations on the centrifuge tubes as volumes. This would simplify everything.
Overnight Anna and I ran on the GC 2 samples each of 1 mL of hexanes transferred using a 1 mL automated pipet and 1 mL hexanes transferred using graduations on a centrifuge tube and spiked all samples with the internal standard at 100 PPB. I wanted to know how accurate the centrifuge tube method was compared to the automated pipet method.
Adama, Marie, and Vieux arrived from St. Louis and performed the solvent cleaning of the 2nd retrieval samples. We will do the dialysis of these samples tomorrow. We will run the calibration standards on the GC tomorrow as well.
No comments:
Post a Comment