What term describes the minimum concentration of a substance that can be measured and reported with 99% confidence that the analyte concentration is greater than zero?

• A. Limit of Quantitation
• B. Method Detection Limit
• C. Lower Warning Limit
• D. Lower Control Limit

Answer: (B)

The key idea is a statistical detection threshold. The term described is the smallest amount of an analyte that can be measured and reported with 99% confidence that the true concentration is above zero. In practice, you determine it by analyzing several low-concentration replicates, calculating the variability (standard deviation) of those measurements, and using the t-distribution to set a cutoff that contains the true value 99% of the time. This yields a detection limit that explicitly ties the reported result to the probability that the analyte is actually present, not just indistinguishable from zero.

This is distinct from the limit of quantitation, which focuses on the concentration at which the measurement is precise and accurate enough to quantify with acceptable uncertainty. It’s also different from the simple detection notions many labs use for signal-to-noise without a tied confidence level. And the lower warning limit or lower control limit are quality-control thresholds, not detection limits for a trace analyte in a sample.

So the described term is the method detection limit.