We face the following problem:
1) It's a general problem faced. During the standard calibration (irrespective of metal), the std. calibration was successful the previous time, but the next time the calibration fails in the same wavelength. Why does this happen?
2) There is the provision to find the concentration of samples from the saved std. calibration. But this is not accurate most of the time. Hence, we are left option less when std. calibration fails at the desired wavelength.
Could someone who has an expertise in running ICP-OES or concepts help us?
Do you use the same standards and it fails or do you prepare fresh standards? You can provide more details for example, is the calibration curve failure or a wavelength calibration failure? First of all read the manual and find the error code and its possible reasons. a) The nebulizer is clogged and the spray does not reach the plasma.
b) One common reason for calibration failure is when the instrument cannot fit a calibration curve i.e. it cannot find an equation which fits your counts i.e. the counts are random as a function of standard concentration.
Never use a stored calibration curves from previous days. Those numbers have no meaning.
please read Instruction manual of the instrument ( ICP-OES) and follow accordingly. Standard and Calibration process play important role in chemical analysis.
You may want to check the flow of the solution into the nebulizer and wait for the reading to stabilize. On the calibration, you may want to plot a calibration curve manually using Excel this is to crosscheck with the calibration curve given by the instrument.
Mr M. Farooq Wahab, Sir, thank you for the clarifications.
The standards used are stored as we were suggested the possibility of doing so. In addition, nebulizer and spray chamber were checked to be working fine.
The failure in the calibration happens at a particular wavelegth. For example, if 'Be' stds, 5, 10, 15, 20 and 25ppm got calibrated at wavelengths 313.107, 313.042 and 234.861nm on one day. the next time the calibrations fail at all/ few of the above mentioned wavelengths. Why does this happen?
Make fresh standards and plot the intensity and concentration in Excel and check the outlier points. Did you check the manual for error code?
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