Gas Chromatography

Summary

This video explains the process of gas chromatography (GC), a technique used to separate volatile organic compounds. The gas chromatograph uses helium as the carrier gas, and a sample is injected into a heated chamber, where it vaporizes and travels through a column filled with absorbent particles. The components are separated based on their physical properties, and GC can also identify compounds with a computer library. The video covers steps for sample preparation, injection, and syringe cleaning, along with operating the chart recorder and handling the chromatograms.

Takeaways

• 😀 A gas chromatograph (GC) is an instrument used to separate and analyze volatile organic compounds based on their physical properties.
• 😀 The gas chromatograph has a column filled with small particles coated with an absorbent layer, known as the stationary phase.
• 😀 Helium is the mobile phase that carries the sample through the column during the GC process.
• 😀 Samples are vaporized in a heated injection chamber before being injected into the chromatograph.
• 😀 GC allows for the determination of relative amounts of product yields and can identify organic compounds when coupled with a computer library.
• 😀 Before using the GC, prepare the sample with a syringe, typically between 1 and 5 microliters of the sample, along with 3 to 4 microliters of air.
• 😀 Ensure that the sample is free of drying agents to avoid clogging the syringe.
• 😀 When injecting the sample, insert the syringe through the septum and be careful not to bend it.
• 😀 Inject the sample promptly, and ensure the entire sample is injected at once for accurate results.
• 😀 Turn on the chart recorder when injecting the sample and check the chart paper feed to ensure it's recording.
• 😀 After injecting, clean the syringe with a solvent like methanol to remove any remaining sample before storing it.

Q & A

What is gas chromatography (GC)?

Gas chromatography (GC) is an analytical technique used to separate and analyze volatile organic compounds based on their physical properties.

What is the function of the gas chromatograph's column?

The column of a gas chromatograph is filled with small particles coated with a thin layer of absorbent, which serves as the stationary phase. This allows for the separation of components in the sample.

What is the role of helium in the gas chromatograph?

Helium acts as the mobile phase in the gas chromatograph, carrying the sample through the column.

How are samples injected into the gas chromatograph?

Samples are injected into the gas chromatograph using a small syringe. The sample is vaporized in a heated injection chamber and then flows through the column with the help of helium.

Why is it important to avoid drying agents in the sample?

Drying agents should be avoided as they can clog the syringe, making the injection process difficult and potentially damaging the equipment.

What should you do after injecting the sample into the gas chromatograph?

After injecting the sample, you should promptly plunge the syringe without bending it, and turn on the chart recorder to begin monitoring the chromatogram.

What should you check before starting the chart recorder?

Before starting the chart recorder, ensure that the chart paper is in place and that it is feeding correctly. If there is no paper or it jams, contact the TA for assistance.

What is the purpose of cleaning the syringe after injection?

The syringe should be cleaned after use to prevent contamination of future samples. This can be done by drawing a solvent, such as methanol, into the syringe and disposing of it in a waste container.

How should the syringe be handled during the injection process?

The syringe should be inserted into the GC injection port carefully, passing through the septum until the glass is flush with the injection port. The syringe should be plunged without bending to ensure that the entire sample is injected at once.

What do you do once the chromatogram has finished running?

Once the chromatogram is complete, turn off the chart recorder, remove the chart paper, and cut it with scissors to separate the chromatogram from the recorder.