Question

"Low concentrations of dioxin near the detection limit gave the following dimensionless instrument readings: 193.3, 156.5, 150.3, 162.3, 207.3, 148.1, 211.1, 189.7, 122.7, and 193.5. Ten blanks had a mean reading of 47.3. The slope of the calibration curve is 2.55 × 10x9 M–1. Estimate the signal and concentration detection limits and the lower limit of quantitation for dioxin."

I know the signal detection limit is yblank + 3s and the concentration limit is 3s/m, but what is ysample to calculate m?

Answer 1

If 135.53 is standard deviation then,

Concentration detection limit = 3 x standard deviation/slope of line

                                              = 3 x 135.53/2.55 x 10^9

                                              = 1.59 x 10^-7 M

lower limit of quantification (LOQ) = 10 x standard deviation/slope of line

                                                      = 10 x 135.53/2.55 x 10^9

                                                       = 5.31 x 10^-7 M