Selecting The Right HPLC Vials For Your Testing Needs

How To Select The Right HPLC Vials For Your Testing Needs

Selecting the right HPLC vials for your lab can be a little tricky…

Especially when there are a lot of things you have to take into consideration like the right material, closure, and even cap to make sure your results are accurate.

And this is really important because if you don’t choose the right one, then some problems can occur like:

• Losing your analyte because of evaporation
• Having your sample degraded
• Damage to your expensive autosamplers
• Or even extra peaks in the chromatogram because of the solvent or septum interaction

And we wouldn’t want to waste time or destroy our precious samples and autosampler, right?

That’s why in this guide, we are going to go over how to choose your HPLC vials so that we can get the best data for your applications.

So let’s get started.

What Should I Consider When Choosing An Autosampler Vial?

These are the main things you want to consider when choosing an autosampler vial:

• Autosampler Compatibility
• Sample Volume
• Sample Compatibility
• Vial Composition
• Glass type
• Autosampler Vial Material
• Caps
• Septa
• Proper Insert

Basically, you want to choose a vial that can contain your sample without affecting it. This can mean making sure that the sample doesn’t leach materials from the vial to making sure it actually fits into your autosampler. 

1. Check Your Autosampler For Compatibility

The first thing you want to do is make sure that your autosampler is compatible with your HPLC vials.

Every company designed its autosampler in a specific way, so you have to use the specific vials it uses to make sure it works.

Think of selecting the right vial as having to use the right batteries for your handheld devices. If you try to fit double-A batteries into a triple-A battery slot, it’s going to be problematic and it probably won’t work.

It’s the same with your autosampler. If you try to forcibly fit HPLC vials that don’t work with your autosampler, chances are it won’t work as it intended (lowers experimental reproducibility) and might break your super expensive autosampler.

So check the compatibility chart for your specific brand.

The reason it’s different is that some of them use robotic arms to pick up your vials while others use tray rotations to move them around. The most common HPLC vials are 12x32mm (2mL) vial configurations) but some of them can use the 15x45mm (4mL) or even the 8x40 (1mL) configurations.

And then you have to consider the type of cap it works with, whether it uses a normal (4mm) or wide (6mm) mouth.

2. Choosing The Right Color For Your HPLC Vial

Choosing the right color is also very important because it might affect your sample. If the UV light starts affecting your sample, then you will analyze the wrong stuff, giving you inaccurate results.

There are two main types of colors used for your HPLC vial:

• USP Type 1, Class A, 33 Borosilicate Glass (Amber glass)
• USP Type 1, Class B, 51 Borosilicate Glass (Clear glass)

So let’s get started to determine which one to select for your needs.
USP Type 1, Class A, 33 Borosilicate Glass (Amber glass)
Amber glass is one of the most widely used glasses in the laboratory, especially for chromatography applications. It’s made up primarily of silicone and oxygen with a little bit of boron and sodium, allowing it to handle being heated to high temperatures without cracking.

The reason you would choose this type of glass depends if your sample is light-sensitive or not.

If your sample is light sensitive, you would want to use this glass so that it prevents your sample from being affected by any UV lights. (That’s why items like the hydrogen peroxide for cleaning at your local CVS use a dark container so that it prevents it from degrading.)

The type 1 amber glass also has a linear coefficient of expansion of 33 and has the lowest leaching characteristics which help keep your sample clean.

What the linear coefficient of expansion means is that it’s just a fancy way of saying how much the glass expands when it is heated. 

This means that a lower number means that it can handle being heated at a higher temperature before expanding and it’s less likely to fracture, making it popular to use in the lab.

USP Type 1, Class B, 51 Borosilicate Glass (Clear Glass)

The clear glass is also made up of silicone and oxygen, with a little bit of sodium and boron.

The main reason you would choose this glass is that your samples aren’t light sensitive and you want more visibility on your samples.

They also have an expansion coefficient of 51, meaning that the max temperature it can be heated is lower than the amber glasses, making it less ideal for substances when you really have to crank up the temperature.

Silanized Glass

Silanized (or deactivated) glass is also another borosilicate glass you can use for HPLC that has gone through further deactivation by treating the surface (or silanizing) the glass with an organosilane. What this does is minimize the adsorption of proteins, peptides, and other compounds and make it more hydrophobic, making it perfect for pH-sensitive compounds, trace analyses or applications that require long-term sample storage.

In other words, it helps keep the integrity for a certain sample for analyzing as well as storing them for long periods of time.

3. Select The Right Closure And Caps

Another thing you want to consider when selecting the right HPLC vials is to make sure that you have the proper closure for them.

Here are the most common ones to use for your lab:

• Screw Top Caps
• Headspace Caps
• Crimp Top Caps
• Snap Caps
• Shell Caps

Screw Top Caps And Vials

These kinds of caps require no special tools to use and are typically used for HPLC and LCMS analysis. They form an excellent seal that helps hold the septum in place when you pierce through it with a needle.

Crimp Top Caps

These caps are great when you need to store a sample for a long time. What they do is they squeeze the septum between the rim of the glass vial and the aluminum cap, preventing any evaporation and stays seated during piercing by the autosampler needle. They are usually used with gas samples for GC or GCMS.

Snap Rings

These caps are much more convenient and even faster to close compared to a screw or crimp top, but they are not as secure. These are typically used for HPLC or any LCMS analysis because all you have to do is simply press it down to seal the vial.

Usually, you would use crimp-cap vials for GC and GCMS analysis while screw-caps are used for HPLC and LCMS applications but the most important thing is to consider your personal taste and the specific experiment you are working on to choose the best vial for you. 

4. Septa Selection

Another thing to consider is the septa selection with the sample or solvent.

This is important when choosing your vial because you want to make sure that there is no sample degradation in your solutions, which can cause fake peaks when you are testing them.

Here are some of the most common materials:

• PTFE
• PTFE/silicone

5. Consider The Insert For Your HPLC Samples

Another thing you want to consider is choosing which insert you want for your HPLC vial.

The reason you want an insert is to help make it easier to recover the sample because it reduces the surface area inside.

There are multiple types of inserts you want to have, which may be:

• Shell-style inserts
• Inserts with springs
• Cone-shaped inserts

For example, flat bottom glass inserts have the largest capacity for filling up your sample so they would be great for being economical, whereas something like a plastic polypropylene insert would be perfect for anything that is pH sensitive.

6. Determine The Right Vial Material

Vial material and choosing the right one is pretty important.

Most of the time, they are made from glass or plastic. Typically, glass is used because they are better at handling heat and the borosilicate glass is better for testing PH sensitive samples.

However, you might use plastic vials since they are:

• More affordable
• Lighter
• And provide a higher chemical resistance. 

Plus, you can use them for samples that are sensitive to or even stick to glass.

The most common plastic vials that you use are polypropylene, as not only do they have good chemical resistance but they can also be incinerated while the samples are sealed, limiting the exposure to hazardous materials for both the people and environment.

Plastic has its own advantages where glass vials would not be suitable for analyzing heavy metal, water and protein, atomic absorption, and ion chromatography.

7. Determine A Consistent Method For Labeling Your HPLC Vials

This one is pretty self-explanatory but you want to consider having a HPLC with either write-on spots or without write-on spots.

If you’re writing it manually, you most likely want to have the write-on spots so you know exactly what samples they are and know what exalt what they are intended for. Otherwise, if you have an automatic label printer, you can get away without the write-on spots.

8. Best Storage Method For Your HPLC Vials

90% of the time you want to store your vials via a tube or vial rack. 

That’s why you want to make sure that any of the racks you purchase actually fit into the rack that you want to store.

Conclusions

Re-using increases the likelihood of contamination from solvent or atmospheric interactions, which can affect your analyses and result in time-consuming and expensive re-work.