Question

A student measured the concentration of a metal in soil samples with FAAS, Reagent blanks give signals of 1.10, 1.90, 1.20, 1.30, 1.60, 1.70, and 1.70 abs units. The slope of the calibration curve is m = 0.325 abs units/ppm. Calculate the average of blank signals with appropriate significant figures. Tries 0/25 Submit Answer Calculate the standard deviation of blank signals with appropriate significant figures. Tries 0/25 Submit Answer Calculate the minimum detectable concentration (detection limit in ppm) with appropriate significant figures.

Answer 1

Average = (1.10+ 1.90+ 1.20+ 1.30+ 1.60+ 1.70+ 1.70)/7

=1.50 abs units

Let x₁= 1.10

Standard deviation, S₁= |x₁-1.50|= 0.40 abs units

S₂ = |1.90- 1.50|= 0.40abs units

S₃= |1.20-1.50| = 0.30abs units

S₄ = |1.30-1.50|= 0.20abs units

S₅= |1.60-1.50|= 0.10abs units

S₆=S₇= |1.70-1.50|= 0.20abs units