Subraction of a blank CF

Hi ,

Custom field required : Area_subr = Area-(BL(Area)) taken blank area from blank injection labelled BL then use this in Y-value for quantification (replace Area with Area_Subtr

Works fine in calibration curve but also subtracts blank area from sample - unknowns

If CF type standards only then does not work (assuming since Blank injection is an unknown)

Only want to subtract blank from standards for quantification purposes

Any ideas ?

Answers

  • Can you call the blank a control? Then set the cf to work for only standards and controls?
  • I tried this but didn't seem to work (no area subtr CF performed)

    Summarise CF with a label for standard 'S' perhaps with blank unknown and types just leave as 'All' in CF , would that work?

    I am not prepared to process again until confident this will work !

  • edited February 6
    You don't need a custom field to do this. Derive a channel that uses blank subtraction. 

    edit: hmmmm... just read past "blank subtraction" and realized you only want this on standards. That's not going to work. You will also be intentionally biasing all of your results if you only correct for standards, which isn't a recommended practice...
  • I require blank area for quantitation

    I was under the impression this was to remove baseline drifts ?!

  • I think I must be over complicating this , surely correction can be made only on standards for calibration curve (Area_Subtr= y value ) and not for unknowns ? 
  • If your Y value is set to Area_Subtract then all of the unknowns will be calculated using this calibration curve too, similar to normal area of unknowns using the calibration curve of area in standards.
  • Hi ,

    Think I have it now

    Do not include AREA_Subtract as part of calibration curve therefore does quantify and subtract blank twice from unknown using CF 

  • Assuming you have no means to improve your chromatography and you have guest peaks adding to your analyte areas, I think the only reasonable strategy is to tick your blank injections, establish the contribution from your matrix/system and subtract it from EVERYTHING. Doing so requires no CFs. 
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