Experiment conducted on September 16, 2024

This lab journal serves as a personal record of experimental work and learning experiences. Some experimental details, procedures, and results have been simplified or omitted. This content is intended for personal documentation purposes only and should not be used as a reference for scientific work or experimental procedures.

Overview

This experiment explored the application of gas chromatography (GC) for qualitative analysis of alkane mixtures. Using retention time analysis, we aimed to identify individual components in various unknown mixtures. The hypothesis centred on the ability to identify compounds based on their characteristic retention times, which was tested using a Shimadzu gas chromatograph GC-2010 Plus with FID (Flame Ionization Detector). The experiment successfully demonstrated the relationship between compounds’ boiling points and their retention times, enabling reliable identification of mixture components.

Method

The analysis was performed using a Shimadzu gas chromatograph GC-2010 Plus with FID. After establishing baseline conditions through system suitability testing and blank analysis, we analysed five different mixtures (A through E). For each analysis, 1 μL of sample was injected following proper syringe cleaning procedures with acetone. The method involved comparing retention times across different mixtures to identify specific compounds, with particular attention to the relationship between boiling points and retention times.

Results

Key findings from the chromatographic analysis:

• Successfully identified multiple compounds in each mixture through retention time analysis
• Observed direct correlation between boiling points and retention times
• Each mixture contained ethyl acetate as solvent (retention time ~10.4 minutes, 80-92% of total peak area)

The chromatogram (Figure 1) showed five distinct peaks with the following elution order:

1. n-hexane (b.p. 69°C) at 10.114 min
2. Ethyl acetate (solvent, b.p. 77°C) at 10.432 min
3. Cyclohexane (b.p. 81°C) at 12.032 min
4. n-heptane (b.p. 98°C) at 11.510 min
5. Toluene (b.p. 111°C) at 13.156 min

This elution pattern largely followed the expected order based on boiling points, with compounds of lower boiling points generally eluting earlier.