Page 13 - Analityka 2/2015

Isotope dilution mass NAUKA
spectrometry: partly lightly
and partly seriously

PART II

In the second part of the article dedicated to isotopic dilution mass spectrometry technique the particular attention
was paid to the aspects affecting the results of the measurements. The effect of discrimination mass was discussed
and the procedure of calculation the Key factor was given. It was stressed that its value should be close to unity,
and the relative standard deviation of all Key factors in one measurement cycle should be lower than 0.5%. To
correct the effect of discrimination mass using IDMS, it is necessary to apply the special measurement sequence,
which was described. Also the monitoring of the background signal in order to avoid contamination before the
next measurement is required. Then, the effect of spectral interference on the calculated value of the isotopic ratio
was mentioned and their elimination necessity. It was emphasized that even if the analytical procedure designed to
remove the matrix provides only the analyte recovery efficiency of 20%, this does not affect the obtained value of
the isotopic ratio. The important advantage of IDMS technique like traceability was highlighted and typical sources
of uncertainty were given. The limitations associated with the use of IDMS were discussed. In conclusion, once
again the great potential of isotopic ratio measurements techniques was underlined.

ANALITYKA – NUMER 2, ROK (XVI) 2015 25