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- Posts: 24
- Joined: Thu Jun 06, 2013 8:05 am
Hello,
I was wondering whether there is an option to get the average noise from the selected chromatogram area in Varian MS Data Review. There is nothing in the manual so it's probably not possible...? The option for calculating noise (ctrl N) gives RMS noise. It would be useful to have the average noise value for the determination of LOD. I could average some noise readings on the both sides of the peak or estimate the ratios by peak-to-peak technique I suppose, however I would prefer to use software if there is such an option.
Could I possibly use the options 'Calculate 5 point RMS Signal/noise' or 'calculate bracketed 10 point RMS Signal/noise' for LOD and LOQ calculations? The obtained ratios are higher than ratios obtained from "visual determination of S/N ratio". So is there any way to convert RMS S/N to manual estimations of S/N?
There are many ways for determination of LOD and LOQ values. The use of calibration curve gave me much higher or lower (depending on which standard deviation I was using, standard error of estimate or standard deviation of blanks, respectively), in comparison to visual determination. Therefore, the visual determination of LOD and LOQ seems to be like a better solution in the case of my analysis (trace levels of VOCs) I think. I know that estimated LOD and LOQ values need validation later but I have to start somewhere.
Thank you for any comments, recommendations, advice.
Kamila
I was wondering whether there is an option to get the average noise from the selected chromatogram area in Varian MS Data Review. There is nothing in the manual so it's probably not possible...? The option for calculating noise (ctrl N) gives RMS noise. It would be useful to have the average noise value for the determination of LOD. I could average some noise readings on the both sides of the peak or estimate the ratios by peak-to-peak technique I suppose, however I would prefer to use software if there is such an option.
Could I possibly use the options 'Calculate 5 point RMS Signal/noise' or 'calculate bracketed 10 point RMS Signal/noise' for LOD and LOQ calculations? The obtained ratios are higher than ratios obtained from "visual determination of S/N ratio". So is there any way to convert RMS S/N to manual estimations of S/N?
There are many ways for determination of LOD and LOQ values. The use of calibration curve gave me much higher or lower (depending on which standard deviation I was using, standard error of estimate or standard deviation of blanks, respectively), in comparison to visual determination. Therefore, the visual determination of LOD and LOQ seems to be like a better solution in the case of my analysis (trace levels of VOCs) I think. I know that estimated LOD and LOQ values need validation later but I have to start somewhere.
Thank you for any comments, recommendations, advice.
Kamila
