Comparing HPLC Vial Types for High-Performance Liquid Chromatography
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An Analysis of the Various HPLC Vial Types for High-Performance Liquid Chromatography

May. 20th, 2024
HPLC is a useful analytical technique. It is applied in numerous scientific fields. Among these are pharmaceuticals, environmental analysis, and food safety. They are essential to the process of analysis. Therefore, choosing the right vial is crucial. It affects the accuracy and reliability of the results.

HPLC vials keep your samples safe from contamination and external influences. You can get these vials in many types, sizes, and materials. They suit different sample types and analysis needs. Each type of HPLC vial offers unique advantages. They have features that help your analysis succeed.

HPLC vials have two main goals. They keep samples pure by stopping contamination and stable. Contamination can have various causes. For example, the bottle material can leach. The bottle surface can interact. Or, the vial can have impurities. To fix these issues, manufacturers use high-quality glass. It has a high boron content and is for making HPLC sample vials. They meet key technical standards. These standards cover the inner and outer diameter of the vial mouth and body. They also cover the accuracy of the threaded mouth. They meet all the requirements of international standards. Each product batch undergoes strict quality control. We have a factory test report. We reduced the risk of sample contamination.

Curious about HPLC vials? Find 50 detailed answers in this article: 50 Most Frequently Asked Questions on HPLC Vials

Another key factor is if it is compatible with the solvents and mobile phases in the analysis. Different vial materials have different chemical resistance to corrosive solvents or high temperatures. Choosing the right vial material keeps the vial from breaking. It also prevents sample damage or contamination.

The closure system of the vial is also critical to keep the sample safe. Septa are typically made from PTFE and silicone, preventing evaporation and reduce the risk of contamination. Good sealing keeps the sample intact. This is key during analysis. It's especially for long runs or volatile compounds.

Sample vials material

Most sample vials are made of glass. The USP (United States Pharmacopeia) classifies laboratory glass by its water resistance.

1. Type I, 33-expanded borosilicate glass

Borosilicate glass USP Type 1, Grade A, 33 is highly inert and widely used in laboratories, especially in chromatography, and consists primarily of silicon and oxygen. It has the lowest resolution and a linear expansion coefficient of 33.

2. Type I, 51-expanded borosilicate glass

This glass is called borosilicate glass USP Type 1, Class B, 51. It is made mostly of silicon and oxygen. It has small amounts of boron, sodium, and more alkali metals than Class A glass. But, it can still be used for laboratories. All amber vials are Class B vials with a coefficient of linear expansion of 51.

3. Polypropylene (PP)

PP is a non-reactive plastic. It has good chemical resistance. It is suitable for short-term storage of most lab chemicals. It can be used where glass is not an option. When using aromatic or halogenated hydrocarbons, resistance decreases over time. PP vials are widely used in ion chromatography. This is because they have low ions and can be cleaned with weak acid and deionized water. Polypropylene vials keep their caps in a fire. This reduces exposure to dangerous substances. The maximum operating temperature is 135°C.

Selection of sample vials made from different materials

a. Glass - universally applicable and acid-resistant;

b.  Amber - for light-sensitive samples;

c.  Polypropylene - for alcoholic samples or water-soluble solvents;

d.   Micro inserts - for very small injection volumes;

e.   High Recovery - for limited sample quantities;

Curious about the advantages of glass chromatography vials over plastic alternatives? Check out our article to discover the key factors that make glass the superior choice for your chromatography applications: Top 3 Reasons Why Glass Chromatography Vials are Better Than Plastic Vials

Types of sample vials

Sample vials are usually divided into three types. These are: crimp cap, screw neck cap, and snap ring cap vials.

How to choose among the three sample vials?

There are three types of caps available for sample vials: crimp caps, snap caps, and screw caps. Each sealing method has its own advantages.

1. Crimp top cap 

The crimp top cap squeezes the septum between the rim of the glass sample vial and the folded aluminum cap. The sealing effect is very good and effectively prevents sample evaporation. The septum stays in place. The needle pierces the sample. Sealing crimp cap vials requires the use of a capper. For a small number of samples, a manual capper is the best choice. For large quantities of samples, an automatic capper can be used.

2. Screw neck cap

The screw neck cap is universal. Tightening the cap squeezes the spacer. It does so by exerting a force that presses it against the glass rim and the aluminum cap. During sampling, the screw cap seals well. It also mechanically holds against the septum. No tools are required for assembly. The screw cap has a PTFE/silicone septum. It is attached to the polypropylene cap using a solvent-free process. This bonding tech keeps the septum and cap together during shipping. It also keeps them together when the cap is attached to the vial. This bonding prevents the septum from coming loose during use. But, the main way it seals is the force when you tighten the cap onto the vial. The cap tightens to make a seal. It also holds the septum in place during needle insertion. Don't tighten the vial cap too much. It will harm the seal and make the septum fall off. If the cap is tightened too tightly, the septum will cup or become indented.

3. Snap ring cap

 The snap cap is an extension of the sealing method of the jaw cover. The cap is plastic. It fits over the vial's rim. It seals by squeezing the septum between the glass and the stretched plastic cap. The tension in the plastic cover is caused by its attempt to return to its original size. This tension creates a seal between the glass, cap and septum. The plastic snap cap snaps on without any tools.

a. The sealing effect of the snap cap is not as good as the other two sealing methods.
b. If the fit of the cap is very tight, the cap will be difficult to close and may break.

c. If it is too loose, the seal will not be effective and the septum may move out of place.

The vial seals better than the bottle. Rubber or silicone re-seal well after being punctured. They are ideal for storing reagents.

However, some solvents will corrode silica gel or rubber gaskets during use. In this case, vials need septa with PTFE coating. If during use, the reagent is not used up at once, but part of it is left in the sample vial for next time. If you use the sample again, This occurs as a result of the pierced septa of the PTFE-coated vial losing its seal.

Rubber or silicone vial septas are resistant to some substances. The best bottles to store them in are those with crimp tops. Corrosive reagents, However, corrosive reagents should not be sealed in crimped bottles. Rubber works better than silicone in terms of sealing.

Unsure about which vial type is best for your laboratory needs? Check out our comprehensive article to learn the unique features and benefits of each option and make an informed decision: Crimp Vial vs. Snap Vial vs. Screw Cap Vial: How to Choose?

In short, HPLC reagent bottles are crucial. They keep samples pure and ensure accurate results. Choosing the right reagent bottle type, size, and material can optimize the results of your HPLC analysis. It can also reduce the risk of errors. It could be a clear glass vial for general analysis or an amber one for light-sensitive samples. Or, it could be a specialty vial for small-volume or pre-slit applications. The right HPLC vials can help any analytical job succeed.