Different Types of Vials: Benefits and Applications

A vial is a small container usually made of glass or plastic. It may be shaped like a tube or bottle and have a flat bottom, unlike common blood collection tubes. Vials are available with various caps to meet specific storage or handling requirements.

Vials are typically used to store medicines or laboratory samples. Although vials are mainly found in the medical field, they are critical to the workflow in various settings, from law enforcement agencies to department stores.

Since there are so many types of vials available, choosing the right one for your lab or business can feel like a challenge. Nevertheless, all types of vials are used to contain a substance securely without enabling adsorption or leaching. It's worth choosing quality vials to protect your samples and products, and prevent reduced productivity in your facility. Once you understand the different materials, benefits and applications, it'll be easier to make that choice.

The Different Vial Materials

Most vials are made of glass or plastic, and the material you choose must be compatible with your samples and storage methods. Any vial used to preserve samples should feature an airtight seal yet allow easy access to the sample. Here are the benefits of glass and plastic vials, and why you might use them in your facility:

Glass Vials

The use of glass vials goes back to ancient civilizations. Egyptians used glass vials to store fragrances and oils. The Phoenicians used glass vials to hold their tears as part of their funeral rituals. For the past several hundred years, glass has been used to store and transport both dry and liquid pharmaceutical products.

Today, glass continues to be the ideal material to store delicate medicines and injectable products, and it is also a commonly used material in general laboratory applications. Glass keeps medicines and formulas safe from environmental factors like light and moisture and allows a long shelf life. You'll find glass containing some of the world's most valuable liquids, from scorpion venom to insulin.

Different types of glass vials are available, and it's critical to select the right kind. Vials may be made of soda-lime glass, the most common and least expensive type of glass, or borosilicate glass. The United States Pharmacopeia (USP) groups glass containers into three categories. According to the USP, borosilicate glass is classified as a Type 1 glass, meaning it is appropriate for most products meant for injection and non-injection purposes. In general, Type 1 borosilicate glass is considered a high-quality vial material.

Borosilicate glass contains at least 5% boric oxide, which increases the vial's hydrolytic and thermic resistance. This type of glass is also valued for its extremely low coefficient of thermal expansion. For this reason, borosilicate glass is widely used in chemical and pharmaceutical industries as laboratory ware.

The USP classifies soda-lime-silica glass as Type II and Type III. Type II features a treatment on the inner surface to boost hydrolytic resistance and may be used for acidic and neutral parenteral products. Type III soda-lime-silica glass is typically suitable for non-parenteral applications.

There are many benefits of glass vials, and they continue to be the material of choice for various applications. Here's what you can expect with glass:

• Clarity: A glass vial features a smooth, clear surface, which allows you to inspect the contents for contamination or degradation. This is one of the reasons glass is the recommended container material for injectable liquids.
• Inertness: Borosilicate glass will not react with other substances, except for a few acids. Therefore, you don't have to worry about borosilicate glass altering your samples, and you can also expect a long shelf life.
• Heat resistance: Borosilicate glass has a low coefficient of thermal expansion and is less vulnerable to thermal shock than other materials. Due to its properties, borosilicate glass is ideal for chromatography.
• Nonporous surface: Glass is nonporous and won't impact the smell or taste of vitamins, medicines or other products stored in a glass vial. It reduces the risk of evaporation or contamination from materials that would otherwise be trapped in a container's pores.
• Recyclable and sustainable material: Glass is recyclable and sustainable and consists of abundant raw materials such as sand. You can feel good choosing glass vials and knowing you are contributing to the health of the environment.

Sometimes iron is added to glass to create an amber tint. This helps protect the stored substance from ultraviolet (UV) light damage. Light-sensitive samples should be stored in amber vials.

Plastic Vials

Plastic vials have dozens of uses. For example, department stores may use plastic vials to contain perfume samples or cosmetics. Laws enforcement agencies use plastic vials to seal and store evidence taken from crime scenes. In a laboratory, plastic vials are commonly used in centrifuges, autosamplers or cryogenic processes. A few substances, such as hydrofluoric acid, must be stored in plastic and not in glass.

Plastic vials are typically made of polypropylene or polyethylene. Polypropylene is a rigid material that may be translucent or pigmented. Polypropylene is similar to polyethylene in many ways. However, it is slightly more resistant to heat. Polyethylene, particularly high-density polyethylene (HDPE), is one of the most common plastics used in bottles and other containers. It's valued for its flexibility and excellent resistance to impact. Both of these plastics are used in a vast range of applications, including medical and pharmaceutical uses. Benefits of plastic vials include:

• Chemical resistance: Except for strong oxidizing agents, polypropylene and polyethylene have excellent resistance to bases, alcohols and acids and have a low risk of leaching. These plastics can be frequently cleaned and sterilized for clinical environments.
• High melting point: Polypropylene has a high melting point compared to other thermoplastics and will soften at around 155 C. Polypropylene is commonly used in autoclaves due to its ability to withstand heat. It also maintains strength in extremely cold temperatures.
• Durable: Plastic is strong and won't shatter, which is one of its greatest benefits. You don't have to worry about samples breaking if an employee drops them or bumps into a vial rack. This increases the safety of your lab and reduces the need to replace lost samples and broken vials.
• Lightweight: Plastic is lightweight and easy to handle, improving efficiency in a busy work environment. Since plastic isn't a heavy material, it's easier and potentially less expensive to ship or transport.
• Affordable: Plastic is a relatively inexpensive material because it costs less to produce than other materials. You can save money by choosing plastic vials while obtaining a quality product that meets your needs.

Plastic vials are available with glass-like clarity or an amber hue if you need a container for light-sensitive substances.

Silicone Vials

Some glass vials undergo a process called siliconization. Siliconization involves applying a silicone solution to the surface of the glass to create a protective layer. The benefits of silicone vials include:

• Minimal interaction between the sample and the vial
• Prevents high-viscosity fluids from sticking to the internal surface of the vial
• Increases transparency

Siliconization can be used to treat amber, borosilicate or soda-lime glass vials and bottles.

Common Vial Types

Although all types of vials are usually made of glass or plastic, they are available in various sizes and designed for specific applications. Always carefully consider how you'll use the vials before making your selection to protect your products or samples. Here are a few common types of vials available, how they may be used and the benefits of each:

Autosampler Vials

Autosamplers automatically and accurately load samples for analysis. It's critical to choose the appropriate vial for autosampler use. The incorrect vial could lead to problems such as sample degradation or damage to the autosampler. Additionally, not all autosampler vials are the same, so you need to consider the type of machine before choosing the vial.

Some autosamplers use robotic arms to pick up vials while others use tray rotation. You'll want to check your autosampler's manual to determine what vial size you need. The type of vial you choose for your autosampler mostly depends on the required diameter.

Regarding autosampler vial material, you can usually choose glass or plastic. Borosilicate glass vials are extremely inert. Use amber borosilicate glass for UV light protection. You might select polypropylene or polyethylene vials for substances that are sensitive to glass or stick to glass.

Cryogenic Vials

Cryogenic vials must consist of materials that can withstand extremely cold temperatures. This may include the storage of biological samples at minus 196 C. By choosing the right vial material, you can protect your samples, lab equipment and employees.

Cryogenic vials are usually made of specially configured polypropylene, and you cannot use glass to store cryogenic materials. You'll also want to include silicone O-rings with the caps to prevent contamination and ensure a tight seal.

Sample Vials

Sample vials are general-purpose containers used to collect, store or transport a range of specimens. You'll find sample vials containing everything from essential oils to crime-scene evidence. Sample vials may be made of glass or plastic and be clear, amber or white. Sample vials may also be autoclavable.

To choose the right sample vial, think about its purpose and the substances it will contain. They are available in various materials, sizes and volume capacities, so you have plenty of options.

You might choose polypropylene vials if you want shatterproof containers for your samples, for example. Borosilicate glass vials may be suitable if you need containers that can withstand higher temperatures than plastic.

Scintillation Vials

Scintillation vials are important components of liquid scintillation counting, or a technique used to measure a substance's radioactive activity. During this process, radioactive samples are placed in glass or plastic vials and loaded into a liquid scintillation counter.

You might choose a transparent low-potassium borosilicate glass vial for this process to allow for easy inspection of the scintillation liquid, or "cocktail." Polyethylene vials may be used as an economical alternative to glass, but are permeable to benzene, xylene and toluene. Most liquid scintillation vials have a volume capacity of 20 milliliters, though they may be smaller.

Other Vials

If you need a specialized vial, it likely exists. Here are a few more types of vials and how they work:

• Filter Vial: A filter vial allows you to quickly and easily remove particulates from samples in a few steps. Typically, filter vials feature a plunger with a filter attached to one end and a cap on the other end. When you push the plunger into the vial, it forces the sample liquid through the filter. With filter vials, you can improve samples, save time and reduce the tools you need. These vials easily fit into standard autosamplers and trays.
• Transport Vials: Transport vials are the ideal shape and size for collecting and transporting general specimens. Transport vials may be self-standing with flat bottoms or have conical bottoms to enable maximum sample recovery. Although borosilicate glass transport vials may be the right choice for certain samples, you might otherwise choose polypropylene to protect samples from breakage as they travel to or from your lab.
• Open-Top Vial: Open-top vials feature an inert polypropylene screw cap. The cap has a hole in the center and a silicone or polytetrafluoroethylene layer, called the septum, underneath. The septum forms an airtight seal. With the open-top cap, an autosampler needle can easily pierce the septum and access the sample. Wide cap openings lower the risk of an autosampler needle bending.
• Low-Evaporation Filter Vial: A low-evaporation filter vial features a special cap to reduce the evaporation rate. The cap is comparable to a standard screw cap but allows for sample filtration.

Vial Inserts

Vial inserts enable maximum sample retrieval and make it easier to remove the contents of a vial. Inserts offer a solution when there is a limited sample amount, and if you plan to use an autosampler for injection because they increase the depth of the sample within the vial. Inserts are typically available in borosilicate glass or polypropylene, and they come in various shapes. Type 1 borosilicate glass is most often used in chromatography, and polypropylene offers an affordable option for use involving pH-sensitive materials.

Common insert styles include:

• Conical: Conical inserts feature a tapered bottom and may come with shock-absorbing springs.
• Flat: Flat inserts have a flat bottom and cylindrical shape. They have the greatest capacity and might be the most economical choice.
• Mandrel: Mandrel inserts have precise tips to reduce the insert's residual volume. You might use mandrel-bottom inserts when you require maximum recovery of a sample.

Vial Caps and Septa

Vial caps play a crucial role in guarding the sample from spills, contamination and evaporation. Ideally, caps should form an airtight seal and be inert. Caps may come with a silicone or polytetrafluoroethylene (PTFE) septum, which creates a tight seal. Needles can pierce the septum because the elasticity of the material allows it to reclose.

Septa are commonly made of PTFE and silicone. There are several benefits of silicone septa. For example, silicone can withstand extremely high and low temperatures and maintain its flexibility. It's also chemically inert and won't impact the sample's integrity. Lastly, silicone is resistant to UV radiation and is suitable for various sterilization methods, including steam autoclaving.

You have many options when it's time to select the septum. Common septum materials include:

• PTFE/Silicone: A PTFE/silicone septum consists of pure silicone laminated with PTFE. This creates a high inertness and exceptional resealing abilities, even after multiple punctures. This is often a preferred choice for chromatography applications.
• PTFE: PTFE septa provide excellent resistance to solvents and are easy to penetrate. However, PTFE septa are not resealable and are recommended only for short-term storage and single-injection use.
• Pre-Slit PTFE/Silicone: Pre-slit septa feature a slit in the center, allowing easier penetration and sample removal. This type of septum is similar to a silicone septum without a slit because it also has excellent resealing capabilities. One difference is a pre-slit septum is slightly less tolerant of aggressive solvents. A pre-slit PTFE/silicone septum may be the ideal choice for improving autosampler reproducibility.
• PTFE/Red Rubber: PTFE/red rubber septa are a popular and affordable option for standard gas chromatography uses. These septa provide moderate resealing capabilities and high chemical inertness. It's not recommended to use PTFE/red rubber septa for multiple injections.

When you choose your vial, it's equally important to select the correct cap. Vial caps are generally available in three types:

• Screw: Most people have used screw caps to close their water or soda bottle. Screw caps for vials are not much different than the bottle caps we use every day. Screw caps are excellent at forming a tight seal. When you turn a screw cap, you apply pressure that holds the septum between the vial rim and the cap, and it won't move when it's pierced. Screw caps may have an opening to use with an autosampler or a solid top for storage purposes.
• Crimp: Crimp caps often consist of an aluminum cap and PTFE/silicone septum. This type of cap tightly squeezes the septum between the vial and the cap, forming a superior seal and reducing evaporation. Crimp caps require the use of manual or automatic crimping tools.
• Snap: A snap cap provides a moderate seal and doesn't require special tools because they can be snapped onto a vial and removed by hand. With an opening in the top, snap caps provide easy access for autosamplers. Snap caps are recommended for short-term storage and can be used with septa and metal O-rings.

What Vial Is Right for Me?

If you're wondering which vial is best for you, know that it depends on several factors. To help you select the correct vial, consider the following:

• Autosampler compatibility: If you need vials to use with an autosampler, make sure you consider the type of autosampler you have and whether it uses robotic arms to pick up vials or trays. If the autosampler uses trays, you'll need to choose vials with dimensions to match the trays.
• Sample volume and composition: Consider the volume of sample and the type of substance you'll be analyzing. For example, if you have a limited amount of the sample, you may have to use an insert with the vial. If you are working with a light-sensitive sample, make sure to choose amber glass.
• Vial and cap material: You'll need to consider a range of factors when thinking about a vial's materials, such as storage methods, chemical inertness and durability. Also, think about whether you plan to use the vial with an autosampler or place it in storage, and choose a cap accordingly. Make sure the cap material is also inert.

If you're still not sure what type of vial you need, let us know at Mercedes Scientific. We are a customer-oriented medical and laboratory supply distributor with nearly 30 years of experience, and we're here to help you make the right selection. Please browse our selection of vials or contact us for more information.