How-to: Manual gas chromatography injections

Summary

This instructional video demonstrates the correct technique for manual gas chromatography injections, emphasizing the importance of reproducible injection volumes and retention times. It guides viewers through the process of syringe preparation, sample loading, and injection, highlighting the need for personal protective equipment, proper syringe handling, and avoiding common pitfalls such as air bubbles and bent needles. The video ensures a thorough understanding of the procedure for accurate and reliable chromatographic analysis.

Takeaways

• 🔬 Always wear appropriate personal protective equipment when working in the lab.
• 🧪 Begin by rinsing the syringe with a suitable solvent to ensure cleanliness.
• 💉 Use a 10-microliter syringe to draw up 6 microliters of acetone and expel it into a waste beaker.
• 🌬 After rinsing, expel several volumes of air and depress the plunger quickly to remove residual solvent.
• 🔄 Rinse the syringe multiple times with the sample to flush out any remaining solvent from the previous step.
• 🚫 Avoid air bubbles in the syringe by drawing up the sample slowly and carefully.
• ⚠️ Be cautious of the syringe needle heating up due to the high temperature of the inlet.
• 🌡 Draw up a volume of air to create a barrier between the sample and the hot needle, ensuring consistent injection volumes.
• 👁️ Keep an eye on the true injection volume, which may be slightly larger than one microliter due to residual sample in the needle.
• 💉 When injecting, use the dominant hand to hold the syringe and the index finger to apply gentle pressure on the plunger.
• ✅ Ensure the syringe is perpendicular to the instrument's top and use the non-dominant hand to guide the needle during puncture.
• 🔥 Pause briefly for the needle to heat up before pushing down the plunger to start the injection process.
• 🏃‍♂️ After initiating the run, quickly and carefully remove the syringe to avoid damage.
• 🚫 Properly guide the needle to prevent bending, which would render the syringe unusable.
• 👆 Apply steady pressure with the index finger to prevent the plunger from bending due to high inlet pressure.
• ❗️ Be aware of common problems such as improper needle guidance or excessive force on the plunger, both of which can damage the syringe.

Q & A

What is the first step to prepare a syringe for gas chromatography injections as described in the script?

The first step is to rinse the syringe with an appropriate solvent to ensure it's clean.

How much volume of acetone is drawn up into the syringe in the demonstration?

Six microliters of acetone is drawn up into a ten microliter syringe.

What is the purpose of expelling the acetone washes into a waste beaker?

Expelling the acetone washes into a waste beaker helps to remove any residual wash solvent from the syringe.

Why is it necessary to drop several volumes of air after expelling the acetone washes?

Dropping several volumes of air helps to quickly remove any residual wash solvent from the syringe.

How many times should the syringe be rinsed with the sample after the initial rinse with acetone?

The syringe should be rinsed with the sample six times.

What is the purpose of drawing up a volume of air after drawing up the sample?

Drawing up a volume of air ensures that the syringe needle is empty and acts as a barrier between the sample and the hot needle, preventing premature vaporization of the sample.

Why is it important to ensure that there are no air bubbles in the syringe before injection?

Air bubbles can affect the injection volume and lead to inconsistent results; hence, it's important to remove them by slowly drawing up and depressing the plunger multiple times if necessary.

How should the syringe be held during the injection process?

The syringe should be held between the thumb and last three fingers, with the index finger applying gentle pressure to the side of the plunger to keep it still during the injection.

What should be done if the gas chromatograph does not have a switch above the inlets?

If there is no switch above the inlets, the syringe should be inserted carefully, the needle should be allowed to heat up, and then the plunger should be pushed down quickly while pressing the appropriate button to start the run.

What is the consequence of not properly guiding the needle during the injection?

Failing to properly guide the needle can cause it to bend, rendering the syringe unusable.

What can happen if too much force is applied while pushing down the plunger?

Applying too much force can bend the plunger, making the syringe unusable and potentially causing the plunger to be blown out of the syringe due to high inlet pressure.