SELF TEST 4.4 – MOOC: Instrumental analysis of cultural heritage objects

Questions about GC-C-IRMS and EA-IRMS.

What is a function of combustion unit in GC-C-IRMS?

Separates isotopes

Burns sample at high temperature to obtain suitable analyte gas for feeding into GC

Cools down the sample

Burns sample at high temperature to obtain suitable analyte gas for feeding into MS

Which of the following statements are true for GC-C-IRMS? (There can be one or more correct answers)

The analytes must be volatile

Specific compound’s isotopic ratios can be measured

Faraday plates are used to detect ions

The sample is usually in solid form

What is the major difference between GC-C-IRMS and EA-IRMS?

GC-C-IRMS measures isotope ratios in single compounds, EA-IRMS in bulk samples

GC-C-IRMS measures isotope ratios in bulk samples, EA-IRMS in single compounds

GC-C-IRMS is used to measure isotopes in gases, EA-IRMS in solid samples

What are the main elements for which isotope measurements are carried out with GC-C-IRMS? (Select all that apply)

What is the δ¹³C related to?

Ratio of ¹²C to¹³C

Ratio of ¹⁴C to ¹²C

Ratio of ¹³C to ¹²C

What is/are the key issue(s) for any type or IRMS? (There may be one or more correct answers)

Ability to measure very accurately the ratios of signal intensities originating from ions with different isotopic compositions

Ability to measure very accurately atomic masses of the isotopes

Ability to measure very accurately m/z ratios of ions formed during combustion processes

Ability to measure very accurately ratios of isotope abundances

Ability to have as high m/z resolution as possible

Carbon originating from C3 plants has more negative 13C value than carbon originating from C4 plants. What does that mean? (There may be one or more correct answers)

C3 plants contain on an average less ¹³C than C4 plants

Isotope fractionation is more extensive in C4 plants than in C3 plants

Isotope fractionation is more extensive in C3 plants than in C4 plants

C3 plants are on an average less rich in carbon

C3 plants contain on an average more ¹³C than C4 plants