The spike recovery equation is usually
% recovery = [(cspiked sample - cunspiked sample)/cadded] x 100%
My professor wrote this equation in our lab manual about spike recoveries and provided the following equation:
% recovery = [(cspiked sample - cunspiked sample)/Δctheoretical] x 100%
And said that Δctheoretical is the theoretical change in concentration calculated based on the known concentration and volume of the spiking solution and the known volume of the sample.
Does anyone know what this means? I thought that cadded was just the concentration added. Do I need to perform some sort of dilution calculation here? I'm very confused, especially because this form of the equation has never appeared in the textbook or any lectures.