HPLC and GC Vials, Caps, Septas and Inserts Guide (Bestsellers 2020)

  A complete guide to autosampler vials concerning about materials, sizes, types and compatibility

A Vial is Small, but Vital Important in Chromatography

• Looking for the perfect vial?

• Struggling to find the “correct” autosampler vial for HPLC or GC?

• You are never alone!

In this article, we aim to discuss the following topics:

• What if I select the incorrect autosampler vials?

• Potential Risks by Using Incorrect Vial/Cap/Septum.

• What are the autosampler vial components?

Part 1 >> Autosampler Vials

What to Consider When Choosing an Autosampler Vial?

►Note: The factors to consider when choosing autosampler vials:

1. Autosampler Vial Compatibility

2. Chromatography Sample Volume

3. Chromatography Sample Compatibility

4. Crimp Vial vs. Snap Vial vs. Screw Cap Vial, How to Choose?

Types of Glass Materials

What is the Linear Coefficient of Expansion and USP Types?

Glass Vials Classifications:

►Type I

►Type II, III and NP

►Special Glasses

AirekaCells® Glass Autosampler Vial Materials

Part 2 >> Autosampler Vial Inserts

What to consider when selecting the HPLC / GC vial insert?

1. Insert Shape and Point Style

2. Solvent Compatibility

3. Dimensions of the Autosampler Vial

Part 3 >> Chromatography Caps and Septas (Closures)

1. Types of Autosampler Vial Closures

►Crimp Vial vs. Snap Vial vs. Screw Cap Vial, Which one to Choose?

2. Autosampler Vial Septas (Septums)

What to consider when selecting chromatography vial septa?

Compatibility of septa and sample

Pre-slit or Not, Which One to Choose?

Storage Considerations for Silicone/PTFE

Part 4 Conclusions:

Some Recommendations about Closure Selection in HPLC / GC

Part 5 Autosampler Vial Product List (Bestsellers)

1. Screw 8-425 (8mm, N8) HPLC Vial, Cap, Septa and Inserts

► 8-425 2mL HPLC Vial without Write-on Spot

► 8-425 2mL HPLC Vial with Write-On Spot

► Closure & Septa for 8-425 (8mm) Screw HPLC Vials

► Insert for 8-425 (8mm) HPLC Vials

2. Screw 9mm (N9) HPLC Vial, Cap, Septa and Inserts

► 9mm 2mL HPLC Vial without Write-on Spot

► 9mm 2mL Vial with Write-On Spot

► Closure & Septa for 9mm Screw HPLC Vial

► Insert for 9mm (N9) HPLC Vials

3. Screw 13-425 4mL Vial, Cap, Septa and Inserts

► 13-425 4mL Vial

► Closure & Septa for 13-425 4mL Screw Vial

4. Snap-Top 11mm (N11) Vial

► Snap-Top 2mL Vial w/o Write-on Spot

► Snap-Top 2mL Vial with Write-on Spot

► Closure & Septa for 11mm (N11) Snap-top Vial

5. Crimp 11mm (N11) Vial

► Crimp 2mL GC Vial w/o Write-on Spot

► Crimp-Top 2mL Vial with Write-on Spot

► Closure & Septa for 11mm (N11) Crimp-top Vial

Part 6 Autosampler Vial Instrument Compatibility

Introduction: 

What if I select the incorrect autosampler vials?

The choice of autosampler vials may seem much less important compared to the significance chromatography instruments many laboratories use. However, the wrong choices of HPLC or GC vials, caps, septas and inserts might well lead to lower experiment productivity and reproducibility or even mechanical damage to the autosampler.

Potential Risks by Using Incorrect Vial/Cap/Septum:

• Loss of samples due to evaporation
• Extra peaks due to solvent↔septum interaction
• Mechanical damage to autosampler
• Sample degradation
• Irreproducible injection volumes

To avoid these risks we need to understand each chromatography vial component in-depth and how to avoid mistakes that might waste your precious samples.

What are the autosampler vial components?

HPLC / GC autosampler vials, caps, septas, and inserts working as a whole to prevent sample degradation and loss of samples caused by evaporation. All components of autosampler vials from AirekaCells^® are designed manufactured by the same level of product standard. Below is an image illustration of each vial components:

We’ll discuss factors that will effect the components below.

Part 1 >> Autosampler Vials

What to Consider When Choosing an Autosampler Vial?

Several factors need to be considered when choosing laboratory glass vials- autosampler compatibility, sample volume, sample compatibility, neck design, vial glass material and especially exposure to heat or freezing temperatures.

►Note: The factors to consider when choosing autosampler vials:

• Contain the sample without allowing it to absorb into the vial
• Reduce the extractable from the vial and septa
• Prevent leaching of materials from the vial

1. Autosampler Vial Compatibility

Not all autosamplers are similar using the same vial specifications. Some is using robotic arms to pick up a sample vial; some use tray rotation, while for others, moving the injection needle to the respective vial coordinates. The design of correct autosampler vials may vary. 

A large percentage of autosamplers are equipped with trays that use 12x32mm 2mL vial but there are instruments, i.e. the Waters Wisp, require a 15x45mm 4mL vial. Check your autosampler operating manual and manufacturer or refer to our autosampler compatibility chart with brand and instrument list to determine the autosampler vial specifications required.

Check a Complete List of Autosampler Vial Compatibility >>

2ml Wide Mouth HPLC Amber Vial

2. Chromatography Sample Volume

The sample amount for chromatography analysis determines the vial volume. For a small limited amount of sample available, vial inserts that are compatible with regular 2ml sampler vials are an decent choice. 

►Which vial is best for my sample size?

There are several factors to consider, including analysis type, analytical platform, and sample availability. AirekaCells® vials offer the same highly consistent performance across the entire size range, from 100μL up to 60 mL. Use the diagram below as a starting point for choosing the size you need based on your sample volume.

Note: Most 12x32 mm autosampler vials hold between 1.5mL to 2mL of solutions. The sizes for 12x32mm vials outer dimensions are standard between manufacturers but the length of the neck and screw thread of the 9mm (N9) vial may vary, because 9mm short thread is not industry standardized. 

3. Chromatography Sample Compatibility

The sample solvent compatibility should be considered when choosing vials and septas. For example, amber glass vials are mostly used for light-sensitive samples while plastic polypropylene vials are used for solutions that are sensitive to glass. Volatile samples require closures that reduce the risk of analyte loss due to evaporation.

4. Crimp Vial vs. Snap Vial vs. Screw Cap Vial, How to Choose?

Vials are available in three closure types; crimp, snap and screw cap. The closures have advantages and disadvantages.

Crimp Vials squeeze the septum between the rim of the glass vial and the crimped aluminum cap. This forms an excellent seal preventing evaporation. The septum stays seated during piercing by the autosampler needle. The crimp cap vial requires crimping tools to carry out the sealing process. For low volume settings, manual crimper tools are the choice. For high volume settings, automated crimpers are available.

Crimp Vial and Cap	Aluminium Crimp Cap	Hand Manual Crimper

Snap Cap Vials are an extension of the crimp cap system of sealing. A plastic cap is stretched over the rim of the vial to form a seal by squeezing the septum between the glass and the stretched plastic cap. Plastic has memory and wants to return to the original dimension. This tension in the cap to return to original size is the force forming the seal between glass, cap and septum. The advantage of a plastic snap cap is no tools are required to assemble. The snap-top cap is a compromise sealing system.

• If the fit of the cap is very tight, they are hard to apply and may be subject to cracking.
• If the fit is too loose, the seal is not very good, and the septa may be subject to dislodging.

Snap-top Vials	Natural Snap Caps	Red Snap Caps

Screw Cap Vials are universal. Screwing the cap applies a mechanical force that squeezes the septum between the glass rim and the cap. Screw caps form an excellent seal and mechanically hold the septum in place during piercing. No tools are required for assembly. 

Amber Screw Vial	Screw Vial Caps	Clear Screw Vials

Note on cap tightening: This is the mechanism that forms the seal and holds the septum in place during needle insertion. There is no need to over-tighten the cap, this can compromise the seal and lead to dislodging. The septum begins to cup or indent when you begin to over tighten.

Quick Comparison of Different Autosampler Vial Designs

Some more tips: 

Based on our years of chromatography vial experience, crimp-cap vials are most situations best for GC and GC/MS analysis, while screw-cap vials are better choice used for most of HPLC and LC MS applications. However, your personal preference and specific chromatography experiment requirements are also important factors to consider.

Snap Cap is fast to seal but sealing strength is not as good as crimp and screw vials. However, even both types of crimp and screw vials have a good seal, crimp vials provide an additional guarantee of sealing for food, forensics, and other applications for which you want to avoid sample tampering. A crimping sealing is also recommended for the storage of volatile compounds. 

Screw HPLC vial	HPLC amber vials	HPLC Compatible Caps

Types of Glass Materials

Different glass bottle materials are available in the market for autosampler vials, the important factors to consider is linear coeffcient of expansion and USP types.

What is Linear Coefficient of Expansion and USP Types?

Linear Coefficient of Expansion refers to the fractional change in the length of glass per degree of change in temperature, in short, the ability of the glass to tolerate rapid thermal changes. The lower the coefficient of expansion the better the glass can handle temperature change without fracturing. Classifications for laboratory glass based on its resistance to attack from water were established by the United States Pharmacopoeia, USP.

Glass Vials Classfications: 

Pharmaceutical glass container materials can be classified as USP Type I, II, III or NP.

►Type I

Borosilicate glass represents the least reactive glass. Type I glass has the least pH shift, lowest leaching characteristics, linear coefficient of expansion 33 or 51, 33 for clear autosampler vials and 51 for amber vials.

USP Type I, 33 Borosilicate Glass is the most inert and chemically resistant glass widely used in laboratories especially for chromatography applications. Type I glass is composed primarily of silicone and oxygen, with trace amounts of boron and sodium. It has the lowest leaching characteristics and a linear coefficient of expansion of 33.

USP Type I, 51 Borosilicate Glass which is composed of silicone and oxygen, trace amounts of boron, sodium and other element is more alkaline than Class A glass but still adequate for laboratory use. All amber borosilicate glass is made of Class B unless otherwise specified and has an expansion coefficient of 51.

►Chemical Composition of Type I Glasses

Chemical Composition (main components in approx. wt %)

Free Ion Content

ND = non detectable results in μg/mL

2ml Clear Screw HPLC Vials

►Type II, III and NP

Type II glass is de-alkalized soda-lime glass with higher levels of sodium hydroxide and calcium oxide. Type III is soda-lime glass - cannot be autoclaved. Type NP is a general-purpose soda-lime glass used where chemical durability and heat shock are not factors. Coefficient of Expansion = 92.

USP Types II, III and NP glass are manufactured from soda-lime which has less chemical resistance than borosilicate Type I glass vials.

►Special Glasses

Silanized or deactivated glass vials are borosilicate glass bottles that have undergone further deactivation by treating the surface of the glass with an organosilane. The surface becomes more hydrophobic and inert making the vial suitable for use with pH sensitive compounds, trace analyses and applications requiring long term sample storage.

Plastic Polypropylene Vials

For some applications glass vials are not suitable due to their composition and their chemical properties. Amongst these are heavy metal analysis, water and protein analysis, atomic absorption, capillary electrophoresis (CE) and ion chromatography (IC). For all these cases high purity polypropylene vials with 0.3 mL, 0.7 mL and 1.5 ml in transparent and amber are available.

Polypropylene Vials with Screw or Snap Neck
Polypropylene (PP) Vials	PP Vial Snap Caps	PP Micro Vials

AirekaCells^® Glass Autosampler Vial Materials

All AirekaCells^® glass autosampler vials are made from USP Type I Glass. Glasses in the USP Type I classification are borosilicate glass with superior chemical resistance. This class of glass represents the least reactive glass containers available. Typically, this glass can be used for most applications, including packaging for parenteral and non-parenteral products. Type I glass may be used to package acidic, neutral and alkaline products. Type I glass can be subject to chemical attack under certain conditions, so container selection must be made carefully for very low and very high pH applications.

Clear Glass vials can be made from a different coefficient of expansion glass; most notable 33-expansion and 51-expansion glass. AirekaCells^® Clear Glass vials are made from Type I glass of 33-expansion glass and type 70 borosilicate glass (budget type). The alkali content is low and 33-expansion glass has very low free ion content.

Amber vials are made from 51-expansion glass which has a different chemical composition and higher free ion content. AirekaCells^® distributes the vials around the world with door to door service. 

Check a List of AirekaCells^® Autosampler Vials. >>

AirekaCells^® Autosampler Vials

Part 2 >> Autosampler Vial Inserts

Limited volume inserts are an economical solution when there is a limited amount of sample and injection is done using an autosampler. Most autosamplers have a set depth that the injection needle can go into the vial without bottoming out. Inserts increase the sample depth within the vial even if there is a very minute volume of sample available.

What to consider when selecting the HPLC / GC vial insert?

1. Insert Shape and Point Style

The style of HPLC / GC vial insert chosen is dependent on the amount of sample available and the residual volume after sampling.

Conical glass inserts have a tapered bottom with pulled tips and are available with or without plastics polypropylene springs. The spring acts as a shock absorber during needle penetration and raises the insert above the bottom of the vial, allowing greater sample recovery.

Flat bottom glass inserts have the largest capacity and are the most economical inserts. These inserts are cylindrical in shape with a flat bottom

2. Solvent Compatibility

Type I borosilicate glass inserts are most commonly used for trace analysis in chromatography. 

Polypropylene inserts are less expensive than glass and are suitable for applications involving pH sensitive samples.

3. Dimensions of the Autosampler Vial

Choosing the incorrect size of the autosampler vial insert can result in poor reproducibility between sample injections, damage to the autosampler needle and an inadequate seal between the septum and the vial.

The dimensions listed for insert size in the article refer to the outside diameter and length. Inserts with an outside diameter of 5mm are used with vials with standard mouth openings and the 6mm are used with wide mouth vials. The length of the insert should be flush with the neck of the vial to prevent the insert from causing the septum to bulge.

Check a List of Stock Available Autosampler Vial Inserts Below >>

Part 3 >> Chromatography Caps and Septas (Closures)

Chromatography vial closures also referred to as seals, are the combination of a cap and septa. To ensure reliable analyses, it is therefore important that all closures are inert and uncontaminated as well as the vial itself.

1. Types of Autosampler Vial Closures

HPLC / GC Vials are available in three closure types; crimp, snap and screw cap. The closures have advantages and disadvantages.

Crimp Caps squeeze the septum between the rim of the glass vial and the crimped aluminum cap. This forms an excellent seal preventing evaporation. The crimp cap vial requires crimping tools to carry out the sealing process.

Snap Caps are an extension of the crimp cap system of sealing. A plastic cap is stretched over the rim of the vial to form a seal by squeezing the septum between the glass and the stretched plastic cap. The advantage of a plastic snap cap is no tools are required to assemble. Snap caps are a compromise sealing system.

• If the fit of the cap is very tight, they are hard to apply and may be subject to cracking.
• If the fit is too loose, the seal is not very good, and the septa may be subject to dislodging.

Screw Cap Vials are universal. Screwing the cap applies a mechanical force that squeezes the septum between the glass rim and the cap. Screw caps form an excellent seal and mechanically hold the septum in place during piercing. No tools are required for assembly. 

Note on cap tightening: This is the mechanism that forms the seal and holds the septum in place during needle insertion. There is no need to over tighten the cap, this can compromise the seal and lead to dislodging. The septum begins to cup or indent when you begin to over tighten.

Quick Comparison of Different Autosampler Vial Designs

►Crimp Vial vs. Snap Vial vs. Screw Cap Vial, Which one to Choose?

Please check answers above >>

2. Austosampler Vial Septas (Septums)

What to consider when selecting chromatography vial septa?

Septa compatibility or chemical resistance with the sample and solvent is the main consideration when choosing vial septa. Any interaction can lead to sample degradation or the appearance of ghost peaks in the testing results.

PTFE is the most inert but its poor resealability making it unsuitable for multiple injections or storage. For layered septa such as PTFE/silicone the chemical resistance of the septa is that of PTFE until the septum is punctured. Once punctured, the silicone layer is exposed and able to react with sample/solvent so the chemical resistance of silicone should be considered when using these septa.

Note: The thicker the facings on the seal the better the resealability but it compromises the ability of the autosampler needle to pierce the septum.

Switch to the desktop version if you cannot view all the information.

Compatibility of septa and sample

Make sure the septa you choose are chemically compatible with your sample and solvent. Chemical compatibility can vary, based on factors such as solvent concentration, molecular weight, and temperature.

►Septa Chemical Compatibility

*PTFE/silicone/ PTFE has the same chemical compatibility of PTFE only until punctured.

“C” indicates that the septa from this category are compatible with the solvent in most configurations.

Pre-slit or Not, Which One to Choose?

Chromatography septas can be pre-slit or not and must be considered by evaluating a few factors. A pre-slit septum is an ideal choice in applications requiring 20% or more of the sample injection each time from the vial so that suction is avoided.

The slit allows ambient gas to equalize the gas in the vial so that a vacuum is not created in the vial from the tight seal around the needle. If coring or clogging from a narrow needle or needle deflection from highly durable septa material is a concern, then choosing a pre-slit septum is a better choice.

The non-pre-slit septas help to reduce carryover from vial to vial because the resealing characteristics of the septum act as a squeegee to wipe solution from the outside of the needle. Typically, a non-slit septum exhibits resealing capabilities for a limited number of needle punctures but for long-term storage in the vial, using a new non-punctured septum is best practice.

8-425 HPLC vials with or without Pre-slit Septa

Storage Considerations for Silicone/PTFE:

Silicone rubber can readily absorb chemicals from the environment. Care needs to be taken in storing caps prior to use. 

►Recommendations include:

• Don't store the septa in locations where chemicals vapor is present for prolonged periods.
• Do not write in the sealed bag with a marker. Solvent vapors will penetrate the bag and be absorbed in the silicone rubber.
• Close a partially consumed bad limiting exposure for prolonged periods.

Part 4 Conclusions:

Some Recommendations about Closure Selection in HPLC / GC

The choice of the best closure depends on certain features of the instrument (needle type / design, transportation mechanism of the autosampler, etc.) as well as on the requirements of the application (temperature, the sensitivity of the analysis, single/multiple injections, etc.) and thus is more complicated and more individual than the selection of the correct vial type.

►Basically the following recommendations can be made:

• Due to the relatively thick and blunt HPLC needles, only Silicone / PTFE closures, either with or without slit, should be used in combination with them.

• Screw thread closures N9 (9mm) 2ml vials and closures are universally suitable on most autosamplers, convenient in handling and available in a broad selection of different cap colors and septum materials. They fulfill all requirements with regard to tightness and analytical purity for GC as well as for HPLC. Due to the relatively thin septa penetration is safe and easy.

Amber 9mm HPLC Vials with Insert

• Crimp closures N11 are also universally suitable with regard to autosampler compatibility, however, they are not as safe and convenient in their closing technique as the screw closures N 9 (9mm) 2ml vials and closures.

• Snap ring closures N11 should only be used in HPLC, as the punctual compacting pressure of the septum against the vial rim by the four pins in the cap does not achieve the same level of tightness as the evenly applied pressure through a screw thread or by crimping.

• For sensitive analyses only high purity Silicone / PTFE closures can be used; if additionally there is a need for minimal coring during penetration, a PTFE / Silicone / PTFE septum (sandwich septum) is recommendable.

• Cap colors may be used for marking (sample marking / lab marking / shift marking). However, please consider that some autosamplers work with photocells which may not be able to recognize transparent caps.

• For sample storage closed top screw closures (without center hole) should be used. Generally, these also need an elastomeric liner for sealing vials with liquid samples tightly.

Close Top Autosampler Vials

• Due to their artificially reduced cap height screw caps N9 don't have a standardized thread design. Therefore, it is recommendable only to use vials and closures from one source of supply, in order to ensure a harmonious and tight matching of both components.

• Replacement septa are partially available, however, in case of manual assembly you have the risk of contamination with skin fat / sweat and of a possible wrong side orientation. Therefore we highly recommend only to use ready assembled closures, where the liner perfectly matches the cap and has been automatically inserted under strict hygienic conditions.

2mL HPLC Clear Vials, Screw

Part 5 Autosamper Vial Product List (Bestsellers)

1. Screw 8-425 (8mm, N8) HPLC Vial, Cap, Septa and Inserts

They are made with a 5.5 mm opening.

These vials are designed to work on most autosamplers that use 12mm x 32 mm crimp style vials. They offer the convenience of screw thread vials for instruments that were originally designed for crimp top vials. They are available in both clear and amber glass.

• Superior quality USP 1 expansion 33 borosilicate clear glass (USP Type 1, Class A) or 51 amber glass
• Uniformly flat bottom for security with inserts.
• Vials feature write-on spot with graduations at 0.5, 1.0, and 1.5ml available.

► 8-425 2mL HPLC Vial without Write-on Spot

► 8-425 2mL HPLC Vial with Write-On Spot

► Closure & Septa for 8-425 (8mm) Screw HPLC Vials

► Insert for 8-425 (8mm) HPLC Vials

• Micro-volume “Drop-In” Inserts for use with Standard 8-425 (8mm) Mouth Vials.
• Compatible with all 2ml Screw Vials, 8-425 Thread
• Center automatically with flat bottom and mandrel interior
• Type I borosilicate glass

2. Screw 9mm (N9) HPLC Vial, Cap, Septa and Inserts

They are made with a 6.0mm opening.

These vials are designed to work on most autosamplers that use 12mm x 32 mm crimp style vials. They offer the convenience of screw thread vials for instruments that were originally designed for crimp top vials. They are available in both clear and amber glass.

Superior quality USP 1 expansion 33 borosilicate clear glass (USP Type 1, Class A) or 51 amber glass

Uniformly flat bottom for security with inserts.

Vials feature write-on spot with graduations at 0.5, 1.0, and 1.5ml available.

► 9mm 2mL HPLC Vial without Write-on Spot

► 9mm 2mL Vial with Write-On Spot

► Closure & Septa for 9mm Screw HPLC Vial

► Insert for 9mm (N9) HPLC Vials

• Micro-volume “Drop-In” Inserts for use with Standard 8-425 (8mm) Mouth Vials.
• Compatible with all 2ml Screw Vials, 9mm Thread
• Center automatically with flat bottom and mandrel interior
• Type I borosilicate glass

3. Screw 13-425 4mL Vial, Cap, Septa and Inserts

Glass autosampler vial, 4ml, 15mm x 45mm, used with 13-425 screw caps.

• Ideal for general laboratory use and sample storage.
• Chemically inert caps suitable for most chromatography and storage applications
• Top grade PTFE/silicone septa used for cleanliness

► 13-425 4mL Vial

► Closure & Septa for 13-425 4mL Screw Vial

4. Snap-Top 11mm (N11) Vial

Snap caps provide a secure seal that minimizes evaporation, even with volatile samples. Snap caps are often more convenient than crimp caps as they can easily be applied and removed by hand. An audible click ensures a secure seal has been formed and that the cap is correctly aligned. Snap/crimp vials can be closed with either snap caps or crimp caps.

• Superior quality USP Type I expansion 33 borosilicate clear glass (USP Type 1, Class A) or 51 amber glass
• Uniformly flat bottom for security with inserts.
• Vials feature write-on spot with graduations at 0.5, 1.0, and 1.5ml available.

They are made wide opening snap-top.

► Snap-Top 2mL Vial w/o Write-on Spot

► Snap-Top 2mL Vial with Write-on Spot

► Closure & Septa for 11mm (N11) Snap-top Vial

5. Crimp 11mm (N11) Vial

We offer the large opening vial with a 6.0 mm opening. These vials are available in both clear and amber glass. The large opening vials are also offered with a write-on spot on the side of the vial for sample identification.

• Available in clear or amber borosilicate glass
• Assembled in polypropylene caps and PTFE/silicone septa
• Directly compatible with autosamplers

► Crimp 2mL GC Vial w/o Write-on Spot

► Crimp-Top 2mL Vial with Write-on Spot

► Closure & Septa for 11mm (N11) Crimp-top Vial

Part 6 Autosampler Vial Instrument Compatibility

This table indicates the categories of vials that are compatible with various models of autosamplers. Certain autosamplers require the purchase of optional vial trays and, in few cases, programming upgrades to use all of the vials listed.

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“C” indicates that the vials from this category are compatible with the autosampler in most configurations.

“H” indicates that a magnetic seal is required for use with the autosampler.

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