"Nearly zero" can be a small positive value. What methodology was used to determine the LOD ?

regards

G

You should list your LOD and LOQ at the top of the report form. For the sample you should report

DEar Joseph Kazery

If anybody evaluate Method Detection Limit (MDL), Limit of quantification (LOQ) or Detection Limit (DL) in correct manner, it should be a positive value and above the zero. Otherwise something is wrong in the determination process.

In addition, you have to use those date very carefully because those sets of data has higher uncertainty

If you do not have proper idea about the MDL/LOQ/DL, you can’t say that it is nearly zero, but you can say that the level is below the lowest reported of their data set.

However, for such occasion, you have to separately motioned those data as “Data with higher uncertainty”.

Piyal Aravinna

Applying mathematical methods, like the determination of LOD and LOQ using the calibration function, negative values can be calculated. They are meaningless in describing the analytical performance of the method/instrument. It is right to be most suspicious regarding such values, as negative values are good indicators for something being "strange" with the analytical method. In several cases it indicates loss of analyte, large uncertainty, or in chromatography the use of inadequate integration parameters (e.g., loosing peak area due to too late integration start or too early integration end)

My suggestion: Revaluate the analytical conditions, or chose a different model on how to determine LOD and LOQ. I would refuse a statement of "nearly zero", as this is guessing, not analytical chemistry - an escape route would be reporting is as "below xxx ng/L" where"xxx ng/L" would be concentration of the lowest calibration standard.

Reality might kick in, and one might be forced by the upper echelon to report such values as they are. In that situation make sure that everybody understands that this is not your work, and any questions need to be directed to the originators.

Hope this is of some help.