Chromatography Forum

Hello everyone

My brain is on a go-slow regarding LOD/LOQ calculation. This is the scenario:
I have a linear calibration curve, measure 6 or more blanks in the same solvent and calculate the LOD from the blank values. Easy.
Now I have a sample preparation, including 10fold enrichment: I extract my samples for recovery (Let's say it is 100 % compared to the calibration in solvent) and also extract the blank matrix in the same way. I measure 6 blank extracts and apply the same formula as above. Do I then have to include the 10fold enrichtment to the LOD value I obtained from calculation or not?

Thanks in advance
Jörg

Yes, you need take the enrichment factor into account, say if you get a 10-ppb LOD from the 6 sample blank extracts, then your LOD in the sample would be 1 ppb.

Hello everyone

My brain is on a go-slow regarding LOD/LOQ calculation. This is the scenario:
I have a linear calibration curve, measure 6 or more blanks in the same solvent and calculate the LOD from the blank values. Easy.
Now I have a sample preparation, including 10fold enrichment: I extract my samples for recovery (Let's say it is 100 % compared to the calibration in solvent) and also extract the blank matrix in the same way. I measure 6 blank extracts and apply the same formula as above. Do I then have to include the 10fold enrichtment to the LOD value I obtained from calculation or not?

Thanks in advance
Jörg

Hello everyone

My brain is on a go-slow regarding LOD/LOQ calculation. This is the scenario:
I have a linear calibration curve, measure 6 or more blanks in the same solvent and calculate the LOD from the blank values. Easy.
Now I have a sample preparation, including 10fold enrichment: I extract my samples for recovery (Let's say it is 100 % compared to the calibration in solvent) and also extract the blank matrix in the same way. I measure 6 blank extracts and apply the same formula as above. Do I then have to include the 10fold enrichtment to the LOD value I obtained from calculation or not?

Thanks in advance
Jörg

You should spike std on blank sample and measure the blank as well as spiked stds. LOD can be calculated from these data.

thohry

The blank determination (7) is applied when the blank analysis gives results with a non-zero
standard deviation. LOD is expressed as the analyte concentration corresponding to the
sample blank value plus three standard deviation and LOQ is the analyte concentration
corresponding to the sample blank value plus ten standard deviations as shown in the
following equations:
LOD ≅ x + 3s
i i b b LOQ ≅ x +10s
where i b x is the mean concentration of the blank and is the standard deviation of the blank.

find below mention link...regarding different approach regarding LOD and LOQ

http://eprints.utm.my/5670/2/MarsinSana ... ession.pdf