Chromatography Forum

Good Day all.

I need to quantity some analyte in my sample. The doubt raised here. If the concentration of few peaks are below than LOD, how should I write this result for precision part,(mean and RSD) in validation report? The distribution of analyte in sample is not equilvalent where increase of dilution factor reduce the visible peaks while reduction in dilution factor make the area of few peaks exceed the range of calibration range. Should I put "below quantification limit"?


**I can increase the peak size in chromatogram either by reducing dilution factor (currently using 1ml to dilute the analyte after evaporation of extraction solvent) or by increase sample amount before extraction.

Your guide noted with thanks.
Thanks all

If you are below LOQ ("Limit of Quantitation") then you are justified in stating just that: "below limit of quantitation". If you are below LOD ("Limit of Detection") then the appropriate phrase is "not detected". You should, of course, run standards at the LOD to justify that level.

Thanks Sir

... and to be prepared for the inevitable "How far below LOQ is the result?", I suggest you report those in-between values as "<X" where X=LOQ - at least this way, they know what the LOQ is.

If you have a decent approximation of your LOD, you could also report as "<LOQ, >LOD", substituting the numbers...

Report any value below the LOQ as Below limit of quantification 'BLQ'
Report any value below the LOD as Below limit of detection 'BLD'

By default, anthing reported as BLQ will have a concentration value between the LOD and LOQ