When performing chromatography or other laboratory analysis, it is essential to acquire the appropriate equipment and accessories in order to optimize sample analysis and ensure accurate data output. Confidence in sample results is a must when performing any of the various types of chromatography analyses. Selecting the appropriate autosampler vials for your analysis is an essential first step in ensuring accurate results. The analytical method chosen will typically determine the size and type of vial required; although at times there may be multiple autosampler vials options available.
2ml autosampler vials
A vial may seem like an insignificant accessory used in chromatography; however it is more than just a temporary container for a chromatography sample or standard solution. Different vials have different properties and characteristics, including composition, size, and type of enclosure, which will affect the outcome of sample results. The most commonly used vials are 12 x 32 millimeter (mm) vials and 15 x 32 mm vials. Depending upon the vial manufacturer, a 12 x 32 mm vial may also be referred to as a 1.5 mL vial, a 1.8 mL vial, or a 2.0 mL vial, so it is important to identify the appropriate vial by its dimensions.
Vial enclosures most commonly found are screw caps and Snap Caps or crimp caps. The screw top is another aspect of the vial that may vary. The size of the screw top is determined by the outer diameter of the opening (or mouth) of the vial. Typical openings vary from 8 to 10 mm, with 9 mm being the most common mouth size used. Crimp or Snap Caps are also options for vial enclosures and are identified as screw caps are, by the outer diameter of the vial mouth. A crimping tool is used to fasten the crimp caps. A Snap Cap manually snaps onto the mouth of the vial to create a seal.
Limited volume vials have a conical glass (or other material) insert fused into the vial. Polypropylene and glass, or a combination of both, is the most common material used in limited volume vials. The inserts are fused within the vial, so there is no prepping the vial by manually adding the necessary insert. This type of vial is available with a screw or a crimp or Snap Cap as well.
The instrumentation and equipment used is also another determining factor in selecting the appropriate vial for your needs. When using an autosampler for chromatography analysis, it is important to identify the limitations of the instrument in order to select the appropriate vials. Each type of autosampler has a different amount of space between the cap and the shoulder of the vial which is required for the instrument to work properly. Some autosamplers may accept different variations of screw top and crimp or snap vials, which should be identified by each manufacturer.
Vials may be clear or amber in color. The amber vials should be used for light-sensitive samples and standards in order to preserve the integrity of the liquid. If the analysis involves a color change identification, clear vials should be used. Ion-exchange chromatography analysis vials should not be glass, so a polymeric or alternative form of vial should be used to maintain the ions in the sample solutions.
Inserts and pre-marked vials are other autosampler vials options available. Vial inserts are cone-shaped with a spring, and they are used to ensure a proper seal with the cap. When used with an autosampler, the insert is desirable because it can adjust to various sampling depths. Again, the instrument used will determine the type and size of insert. Pre-marked vials are marked at different sample depths (0.5 mm, 1.0 mm, etc.) for easy filling and identification of liquid volume in the vial.
Various cap enclosures are also available that consist of a cap and a cap liner. The liner acts as a septum where a syringe can pull the liquid through the cap while it is still sealed to the vial. Once again, with caps and cap liners, there are a variety of different compositions and properties available, depending on your needs. Cap liners are typically made of rubber or silicone, and are sometimes lined with PTFE (polytetrafluoroethylene). The type of liner chosen should be compatible with the desired sample analysis.
Many chromatography methods required headspace vials. Headspace vials are typically either 75 mm x22 mm or 45 mm x 22 mm in and take a 20 mm closure, although as with other aspects of vials, it depends on the sample analysis and the instrumentation used. Headspace samples are filled to the rim with no room for air when the vial is capped, and then they are heated during the chromatography process to release volatile organic solvents. The shape and characteristics of the headspace vials should be considered in addition to instrument requirements.
Ferrules are another vital accessory to optimal chromatography analysis that is often overlooked. The need for tightly sealed, leak-free gas flow is essential in chromatography analysis. Ferrules provide the appropriate tube/column seals with fixtures that withstand the high pressure and high temperature chromatography environment. The advantage of using ferrules is that they are easily interchangeable and be applied and removed easily, so adjustments can be made based on sample method requirements.