MOOC: Instrumental analysis of cultural heritage objects

SELF TEST 6.1

Questions about practical aspects of chromatography.

Using the HPLC technique, you have to determine the lipid components in a paint sample taken from a 20th century painting. Which of the following statement is true?

Non-polar solvent (e.g., hexane, tetrahydrofuran) is used for extracting the lipids. The analysis is carried out with RP-HPLC.

A multi-step extraction is needed to extract the lipids, starting with a mild solvent (like ethanol), finishing with a strong HCl solution. The analysis is carried out with NP-HPLC.

Lipids are extracted with water from the paint sample. The analysis is carried out with SEC.

Choose the correct statement that applies to analysing samples with HPLC. (There can be one or more correct answers)

Insoluble samples can be analysed

Sample must be fully dissolved and should be filtered prior to injecting into the system

The analysed sample solution must be clear and without any colour

At least 5 ml of sample solution is needed

A wide variety of compounds with different chemical properties can be analysed

Analysed compounds must be volatile

Match the material under the investigation to the preferred GC method.

Volatile degradation products from paper	GC-MS and Py-GC-MS Unselect SPME GC-MS Unselect GC-MS Unselect Py-GC-MS Unselect
Aged synthetic acrylic paint	GC-MS and Py-GC-MS Unselect SPME GC-MS Unselect GC-MS Unselect Py-GC-MS Unselect
Dried linseed oil from the oil paint	GC-MS and Py-GC-MS Unselect SPME GC-MS Unselect GC-MS Unselect Py-GC-MS Unselect
Fresh poppy oil	GC-MS and Py-GC-MS Unselect SPME GC-MS Unselect GC-MS Unselect Py-GC-MS Unselect

Why is derivatisation used with GC analysis? (There can be one or more correct answers)

To improve the separation of different compounds

To increase the volatility of the compounds

To increase the thermal stability of the compounds

To decrease the volume of the sample solution

To decrease contamination in the instrument

To increase the solubility of the compounds

To increase the peak heights of the compounds

To decrease the adsorption of the compounds in the injector

Which of the following procedures improves the GC analysis of poorly volatile compounds? (There can be one or more correct answers)

Increasing the temperature in the oven

Derivatisation of the compound

Using Py-GC with derivatisation reagent

Using a C-18 column

Using solid phase extraction

Derivatization(s), where –CH₃ group is added, include... (there can be one or more correct answers):

acid-catalysed methylation (ACM)

derivatisation with TMAH

liquid-liquid extraction

two-step derivatisation with BSTFA

Find the most suitable LC separation method for the materials.

Dyes extracted from fibres

Synthetic polymers|such as PVAc glue

Protein-based binders (e.g.|egg white|egg yolk) from paints

Resinous compounds extracted from pine tar

Oil and fat residues extracted from pottery

Are the following statement true or false?

With GC-FID|a compound can be identified only by comparing its retention time to the retention time of

the corresponding standard.

LC-MS is only suitable for the qualitative analysis of volatile organic materials (acetic acid|alkanes|

monoterpenes|etc.).

With GC-MS|the identification of compounds can be verified with the help of a mass spectral database.

GC-MS is more suited for the analysis of complex samples (e.g.|aged binding materials with unknown

composition) than GC-FID.

GC-MS is more suited for the analysis of aged natural oils|fats|and natural resins than RP-HPLC-MS.

GC-MS is suitable for the qualitative analysis of pigments like zinc white|chromium oxide green|cinnabar.

RP-HPLC with UV-Vis/PDA detector is suitable for the quantitative analysis of textile dyes (madder|indigo|

cochineal|etc.).

RP-HPLC-MS is more suited for the analysis of aged and/or polymerized materials (aged oil paint|modern

alkyd varnish|etc.) than Py-GC-MS.

GC-MS is suitable for the quantitative analysis of amino acid derivates obtained from the hydrolysis and

derivatisation of proteins.

A varnished wooden chair is exhibited in a glass box in a museum. Which GC method would be the most suitable for the described aim?

Determine if and what chemicals are in the air of the box.

Analyse a small piece of the wood without additional sample pre-treatment.

Identify if the varnish contains drying oil and if yes|identify all components of the drying oil.

Determine if the varnish contains synthetic polymers.

A solution of organic compounds dissolved in hexane has been analysed with GC-MS. Please interpret the obtained chromatogram below and choose the correct compound (marked as A, B, C, D, or E) suitable for the description.

chromatogram_self_test

The compound has the lowest boiling point.	C Unselect E Unselect D Unselect A Unselect B Unselect
The compound spent the longest time in the stationary phase.	C Unselect E Unselect D Unselect A Unselect B Unselect
The compound exited the column second.	C Unselect E Unselect D Unselect A Unselect B Unselect
From this compound, the highest number of ions was detected.	C Unselect E Unselect D Unselect A Unselect B Unselect
The compound has a retention time of 17.44 minutes.	C Unselect E Unselect D Unselect A Unselect B Unselect

Course introduction
1. Overview of materials and techniques
2. Optical microscopy
3. Vibrational spectroscopy
- 3.1. IR Spectroscopy
  - * SELF TEST 3.1
- 3.2. Raman spectroscopy
  - * SELF TEST 3.2
4. Elemental and X-Ray methods
5. General aspects of chromatography and mass spectrometry
- 5.1. Chromatography
  - * SELF TEST 5.1
- 5.2. Mass spectrometry
  - * SELF TEST 5.2
6. Practical aspects of chromatography and mass spectrometry
- 6.1. Chromatography
  - * SELF TEST 6.1
- 6.2. Mass spectrometry
  - * SELF TEST 6.2
7. Multimethod analysis
Glossary
Acknowledgements
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