detection limit study on 7900

Hi Everyone,

I was wondering if everyone uses the detection limit of instrument or do you do separate detection limit study? 

If so could you please tell me about the detection limit study you do? Do you use typical methods? 

Thank you so much! 

  • What industry are you in? 

    I come from EPA where we were required to run both IDL (Instrument detection limit) and MDL (method detection limit). 

    IDL was running 10 blank solutions, calculating Standard deviation of the 10 and multiplying by students t (3) for the IDL. 

    The MDL was run by multiplying the IDL by 3 to 5 and rounding to a whole number for a concentration to spike into solution.  i.e. IDL =0.07ug/L we would spike at 0.3 ug/L.  This solution is then split into 7 vessels and taken through the digestion process.  Again, standard deviation of the 7 samples was multiplied by students t (3.143) to get the MDL.  

    You can improve these by using longer integration time for a mass.  Rule of thumb, to cut SD (which is proportionate to DL) in half you need to integrate 4 times longer.  So if you currently have the time set to 0.3 seconds, increasing to 1 will improve your DL.

    I don't know the regulations for ASTM (oils) methods, or USP (pharmaceutical) methods.  If you are in these industries check the methods for determining detection limit, sometimes called LOD (limit of detection).

  • Please refer to.. 

    Reference: ICH Q2 Validation of analytical procedures

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