Hello community,
Customer is experiencing problem with calibration of gold standards extracted with the solution of toluol and oil sulfide.
They have next standards: 0.05 ppm, 0.1 ppm, 0.5 ppm, 1 ppm and 5 ppm.
Steps they follow:
1. Optimize the signal using 1 ppm to get about 0.032-0.033 abs. And then check for 5 ppm that gives about 0.155-0.165 abs.
2. Start calibration and two scenarios happen:
a) Signals for standards give lower values than it was while optimization. For example 1 ppm gives 0.028-0.029 abs and 5 ppm can drop to 0.125-0.135 abs. In this situation calibration curve is not obtained. So signals drop down after the optimization and trying to get calibration.
b) Calibration can be done successfully, but measuring the standards used for calibration give the bad values. For example 0.5 ppm can give the value as 0.54 ppm concentration, 1 ppm gives 0.95 ppm (with signal of 0.029-0.030 and 5 ppm can give 4.7 ppm (signal is about 0.140-0.145 or even less). So signal values also drop down during the measurement after calibration.
At this moment they can not use the instrument because of this unstable signal issue.
What can be the reason for such a signal decrease?
You can find some attached worksheets to get a better understanding.
Thank you in advance.
