Generally

the isotope abundance of a compound labelled with stable isotopes can be calculated using Biemann's method. But there are some proton adducts mixed with the fragments of mass spectra

which make the error increase when calculating the isotope abundance

In order to decrease this error

we have developed the data analysis method of mass spectra to the molecules labelled with up to 4

5

6 or 7 deuterium atoms respectively. This method will eliminate the error caused by proton adducts and is very useful in the determination of compounds labelled with stable isotopes

especially amino acids. labelled with

2

H. A program is made by means of the Newton iteration method.