Difference from Background: Limit of Detection

Background noise is intrinsic to any measurement interfering with the detection of the analyte signal. To analyze if the measured signal is from the analyte or only noise, the limit of detection is calculated. The limit of detection is the lowest quantity of analyte detected, whose signal is distinct from the background noise. The LOD is calculated based on the standard deviation of the blank signals and the slope of the calibration curve.  This value corresponds to the concentration at which the analyte's signal is thrice the standard deviation of the blank signal. Below this value, the analyte signal cannot be differentiated from the background noise. Likewise, the limit of quantification value corresponds to the concentration at which the analyte's signal is ten times the standard deviation of the blank signal. The LOQ is the lowest quantity of analyte that the instrument can quantify with reasonable accuracy and precision.