Quiz: Sampling

Multiple choice: Check your answers by clicking on them.

1.The liquid sample you collected from a nearby river is highly contaminated with dissolved compounds. Which sample preparation methods do you consider to purify your sample to be finally able to analyze your analyte of interest? Select one or more:
Gas chromatography
Preparative HPLC
Solid phase extraction
Mass spectrometry
Liquid-liquid extraction
2. Decide whether a statement is true or not. A sample is …
… a preferably large part which is collected to represent the whole.
… a subset of manageable size of a population.
… taken in order to identify patterns.
… collected and selected by a random procedure.
3. What are characteristics of a heterogeneous sample? Select one or more:
The sample is representative for the whole.
Two samples can have different compositions.
You need to homogenize the sample.
The sample has a uniform composition.
Independently taken samples may be hard to compare.
4. What is a postive sampling artifact?
Loss of analyte which results in a lowered finding of the analyte
Additional entry of analyte which results in an exceeding finding of the analyte
An analytical error
5. A selection of sample preparation steps, which you may need to conduct before analysis. Select one or more:
Modification of the analyte, e.g. derivatization for gas chromatography
Homogenization
Sample purification
Removal of salts and other contaminants
Increase of analyte concentration
Change of solvent matrix
6. What does SPE stand for?
Sample preparation evaluation
Solid phase extraction
Solid phase evaporation
Sample processing experiment
7. Select one or more correct answers about lyophilization.
The material is spray-dried, accompanied by a pressure drop.
Lyophilization is a dehydration process.
Lyophilization results in a change of structure of the solid material.
Frozen water of the sample is sublimated.
8. How do you call a sample with a uniform composition?
homogenous
unigenous
monogenous

Fill in the gap: Toggle down to check your result.

1. Bring the steps of an analytical process as well as its characteristics into the right order by matching the numbers with the words below.

analytical process_characteristics

a) data evaluation, b) documentation and final conclusions, c) sample processing, d) qualitative or quantitative analysis, e) statistics, f) conclusion on content, g) evaluation of statistical significance, h) representative and homogeneous, i) sample preparation, j) sampling, k) report, l) experiment/ analysis

Solution

1j, 2h, 3i, 4c, 5l, 6d, 7a, 8f, 9e, 10g, 11k, 12b

2. Match the provided “sample preparation & processing”, “detection” or “separation techniques” with the examples below.

Post-sampling steps

a) optical methods, b) extraction, c) sonification, d) thin-layer chromatography, e) liquid chromatography, f) lyophilization, g) gel electrophoresis, h) atomic spectroscopy, i) homogenization, j) photometry, k) gas chromatography, l) mass spectrometry

Solution

1bcfi, 2degk, 3ahjl

3. The provided images depict different levels of accuracy and precision, which can be transferred to actual analytical experiments. Match the numbers in the boxes with the description below.

accuracy_precision

a) low accuracy and low precision, b) high accuracy and high precision, c) low accuracy and high precision, d) high accuracy and low precision

Solution

1b, 2d, 3a, 4c

4. Match the numbers in brackets with the words below.

Homogenization is the (1) and therewith homogenization of the sample, e.g. by mechanical methods like (2) or (3). The sample changes its (4) properties but maintains its general (5).

a) ultrasonic, b) disruption, c) analysis, d) shaking, e) milling, f) physical, g) chemical, h) physical properties, i) chemical composition

Solution

1b, 2a, 3e, 4f, 5i

5. Bring the steps of a solid phase extraction into the right order:

[Loading of sample onto the column], [preconditioning of the SPE column], [elution of analytes], [column is washed to remove impurities like e.g. salts/ analytes remain on the column], [sample compounds interact with the stationary phase of the column]

Solution

[preconditioning of the column], [loading of sample onto the column], [sample compounds interact with the stationary phase of the column], [column is washed to remove impurities like e.g. salts/ analytes remain on the column], [elution of analytes]

6. Match the numbers in brackets with the words below.

With liquid-liquid extraction compounds contained in one solution are transferred into (1), which is (2) with the (3). This method separates compounds based on their (4).

a) solubility, b) the gas phase, c) feed solution, d) another solvent, e) immiscible, f) miscible, g) analyte

Solution

1d, 2e, 3c, 4a

7. During sampling and sample analysis procedure different errors may occur, which however affect the experimental outcome to different extents. Match the numbers in the boxes with the words, which corresponds to the extent of the experimental error depicted in the graph underneath.

sampling error

a) analysis, b) sampling, c) sample preparation

Solution

1b, 2c, 3a

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