14. A procedure was used in which electric current in a detector is proportional to analyte concentration. From previous measurements of a low concentration of analyte, the signal detection limit was estimated to be in the low nanoampere range. Signals from six replicate samples with a fixed analyte concentration about four times the detection limit were 6.1, 6.2, 5.4, 5.6, 6.6, and 5.1 nA. The standard deviation of the mean of these values computes to be 0.54 nA. Reagent blanks gave values of 1.0, 2.1, 1.9, 0.8, 1.4, and 0.9 nA. The average of these values for the blank is 1.35 nA. The slope of the calibration curve for higher concentrations is m = 0.472 nA/pM.

(a) Find the signal detection limit and the minimum detectable concentration.

(b) What is the concentration of analyte in a sample that gave a signal of 8.5 nA?