**6.4 Limit of detection**

The limit of detection is the lowest content of analyte that can be distinguished from background noise and measured with reasonable statistical certainty. It can be calculated by the reduced formula:

$$\mathbf{3} \mathbf{S} \mathbf{B} / \mathbf{b} \tag{4}$$

Where SB = Sy/x (calculated from the regression analysis data), b is slope [29].
