A sample is to be analyzed following a prescriptive quality assessment protocol with a detection limit for the method of 0.05ppm. The calibration curve relationship is S means= 0.276X (ppm analyte)
Afield blank is spiked with the analyte to a concentration of 2.27ppm and returned to the lab. Analysis of the spiked field blank gives a signal of 0.57. If the limits for a sucessful spike recovery are +/- 10%, is the result acceptable?
To determine if the spike recovery result is acceptable, we need to calculate the percentage spike recovery and compare it to the acceptable range of +/- 10%.
First, let's calculate the expected signal for the spiked field blank.
Given that the relationship between the signal (S) and analyte concentration (X) is S = 0.276X, we can substitute the concentration of the spiked field blank (2.27 ppm) into the equation.
Expected signal = 0.276 * 2.27 = 0.62772
Now, we can calculate the percentage spike recovery using the following formula:
Spike recovery (%) = (Measured signal / Expected signal) * 100
Spike recovery = (0.57 / 0.62772) * 100 = 90.88%
Since the spike recovery of 90.88% is within the acceptable range of +/- 10%, the result is considered acceptable.