What describes the lowest concentration of analyte that can be accurately and precisely measured, determined as the mean of signal intensity plus 10 standard deviations?

The correct answer is Limit of Quantitation (LOQ). This term specifically refers to the lowest concentration of an analyte that can be reliably quantified with acceptable precision and accuracy within a given analytical method. The definition you provided, stating it is determined as the mean of signal intensity plus 10 standard deviations, aligns well with how LOQ is characterized.

In analytical chemistry, LOQ is a critical parameter because it sets the threshold at which the measurement can be considered both accurate (reflecting the true concentration) and precise (being reproducible). The use of 10 standard deviations emphasizes a stringent approach to ensuring that the signal differentiated from background noise is strong enough to guarantee reliable quantification.

In contrast, other terms such as Limit of Detection (LOD) relates to the lowest amount of analyte that can be detected but not necessarily quantified with precision. This distinction is crucial because while LOD indicates the capability to observe the presence of an analyte, LOQ confirms the quality of the numerical measurement of that analyte at low concentrations.