The following describes calculations that are done for an isotope ratio analysis.
Mass bias correction factor for the numerator =
(Abundance ratio of the numerator mass / (Total of the CPS counts of all points for the numerator mass in the standard data))
Mass bias correction factor for the denominator =
(Abundance ratio of the denominator mass / (Total of the CPS counts of all points for the denominator mass in the standard data))
First calculate the isotope ratio for each replicate data.
(1) Correct the mass bias for the numerator
Corrected numerator data =
(Total of the CPS counts of all points for the numerator mass of the sample) x (Mass bias correction factor for the numerator mass)
(2) Correct the mass bias for the denominator
Corrected denominator data =
(Total of the CPS counts of all points for the denominator mass of the sample) x (Mass bias correction factor for the denominator mass)
If you select "Total" for the denominator mass, apply the above correction to all isotopes, and calculate the total of the corrected values. For example, if there are three isotopes, calculate as follows.
Corrected "total" data =
(Total of the CPS counts of all points for the isotope 1 in the sample) x (Mass bias correction factor for the isotope 1)
+
(Total of the CPS counts of all points for the isotope 2 in the sample) x (Mass bias correction factor for the isotope 2)
+
(Total of the CPS counts of all points for the isotope 3 in the sample) x (Mass bias correction factor for the isotope 3)
(3) Calculate the isotope ratio
Isotope ratio = (Result of (1)) / (Result of (2))
From the isotope ratios of all replicate data calculated based on the Step 1, calculate the average and SD.