I spent the first half of the day today organizing and analyzing the results from yesterday's samples. The results I received for the predicted concentrations of my soultions were pretty consistently 5% away from the values that I expected. This may be a problem with my preparation of the solutions, or it could be an issue with the calibration or conditions of the machine. In particular, the axial readings for the Magnesium concentrations were consistently 30%+ away from the expected value. For the most part, these results should be ignored because they are oversampled. Also, I found that consistently the first sample I tried to run was not drawn from the test tube, which led to a lot of strange negative results for one of the samples.
To try an look further into these issues, I prepared and tested a large new set of samples. This new set has two magnesium series, a cobalt series, and a phosphorus series. This should help identify where some of the 5% error is coming from. If it is a problem with the machine or the range of concentrations we are running, more data will make this easier to see. If it is a problem with my preparation, this will also become obvious. I ran the tests at the end of the day yesterday, and will analyze the data tomorrow.
Also, we are looking at changing the calibration method for the tests, because of the strange magnesium readings we were getting for the axial view. It is possible to use a non-linear fit for the calibrations, and we will see if this helps tomorrow.