Which statement differentiates LOD and LOQ?

Which statement differentiates LOD and LOQ?

• A. LOD is the lowest concentration detectable; LOQ is the lowest concentration that can be quantified with acceptable precision and accuracy
• B. LOQ is the lowest concentration that can be quantified with acceptable precision and accuracy; LOD is the lowest concentration detectable
• C. LOD is the lowest concentration that can be quantified; LOQ is the lowest concentration detectable
• D. LOD and LOQ are the same concept

Answer: (B)

The key idea here is understanding the difference between detecting presence and reliably quantifying amount in an analytical method. The limit of detection is the smallest concentration that can be reliably distinguished from the background noise—it's about detecting that something is there, not measuring how much with precision. The limit of quantification, on the other hand, is the smallest concentration at which you can quantify the amount with acceptable precision and accuracy. Because quantification requires a stronger, cleaner signal, LOQ is higher than LOD.

So the best description is that LOQ is the lowest concentration that can be quantified with acceptable precision and accuracy, while LOD is the lowest concentration detectable. In practice, if a sample sits around or between these levels, you can detect its presence (above LOD) but may not report a reliable amount until you reach LOQ. The other statements would blur or reverse these roles or say they’re the same, which isn’t correct.