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The diagram below represents a gas chromatograph - VCE - SSCE Chemistry - Question 1 - 2002 - Paper 1
Question 1
The diagram below represents a gas chromatograph. **a.** Clearly identify, on the diagram, the mobile and stationary phases in the gas chromatograph shown and expla... show full transcript
Worked Solution & Example Answer:The diagram below represents a gas chromatograph - VCE - SSCE Chemistry - Question 1 - 2002 - Paper 1
Step 1
Clearly identify, on the diagram, the mobile and stationary phases in the gas chromatograph shown and explain how gas chromatography is able to separate the components of a gaseous mixture.
Answer
In the gas chromatograph diagram:
- The mobile phase is represented by the carrier gas, which is nitrogen (N₂) from the cylinder.
- The stationary phase is typically a liquid coated onto the inner wall of the column.
Gas chromatography separates components of a gaseous mixture based on the different rates at which they migrate through the stationary phase. As the sample mixture is carried by the mobile phase, the various components interact differently with the stationary phase. Components that have a stronger affinity for the stationary phase travel more slowly, while those with a weaker affinity move faster. This differential migration results in the separation of the components along the column, allowing them to be detected at different times.
Step 2
How many peaks would you expect to see in the resulting chromatogram? Justify your result.
Answer
For Stanozolol, which is a pure substance, we would expect to see a single peak in the resulting chromatogram. This is because a pure compound elutes at a definite retention time, corresponding to its unique properties. Thus, the presence of just one peak indicates that only one substance is being detected.
Step 3
If a sample of pure Stanozolol were available, how could it be used in the gas chromatograph to confirm the identity of the suspect sample?
Answer
To confirm the identity of the suspect sample using the pure Stanozolol, one could perform a comparison of the retention time of the suspect sample to that of the pure standard. If the retention times match, it suggests that the suspect sample is indeed Stanozolol. Additionally, a comparison of the area under the peaks can provide quantitative information to support the identification.