Helpful Fluoropolymer Tubing Guide for Your HPLC Applications
What types of tubing are used in the laboratory?
In liquid chromatography and other fluidic laboratory applications, you can choose from a wide variety of tubing materials, sizes, and other specifications. Chemical compatibility, pressure limits, and other factors such as internal diameter or optical clarity requirements all play a role in choosing what tubing will work best for a given application. With that being said, what are the various tubing types available to use? There are stainless steel and other metallic, high-pressure options, as well as polymeric tubing for high and low pressures. A sub-category of polymeric tubing is low pressure, fluoropolymer tubing.
"Chemical compatibility, pressure limits, and other factors such as internal diameter or optical clarity requirements all play a role in choosing what tubing will work best for a given application"
What is fluoropolymer tubing?
Fluoropolymers are fluorocarbon-based polymers that contain multiple carbon bonds. Polytetrafluoroethylene (PTFE) is the most well-known fluoropolymer, and it’s very commonly used in lab supplies such as tubing, fittings, and other consumables. Fluoropolymer tubing is specifically designed for fluidic applications that are more critical, with low and medium pressures. These tubing materials are generally translucent to transparent, making it easy to visibly see the fluids flowing through the tubing. They’re also very chemically compatible, making them good choices for many fluidic applications.
Are there different types of fluoropolymer tubing?
There are many different types of fluoropolymer tubing, and we offer a wide variety of materials including PFA and high purity PFA, FEP tubing, and ETFE tubing, making our fluoropolymer tubing a clear choice for many applications.
- PFA tubing is a very chemically compatible option due to its inner surface smoothness It also tends to be more translucent than PTFE tubing, making it a great choice for monitoring fluid movement. It is best for low pressure applications (500-2,000 PSI).
- We also offer a premium grade PFA, which is one of the most contaminant-free polymers available. It’s a great replacement for PTFE where gas permeability and surface texture are issues.
- FEP tubing is chemically inert to most solvents, easy to cut, and is also translucent for visualization of fluid movement. It’s available in many different sizes and colors for easy identification. Also, the manufacturing tolerances are quite tight to ensure product consistency. The pressure limit of FEP is higher than PFA, from 2,500 up to about 4,000 PSI.
- ETFE is a more ridged tubing, which is good for resisting inner diameter collapse. It has excellent solvent resistance and is more suitable for higher pressure applications (500-4,000 PSI) when using aqueous mobile phases.
When is fluoropolymer tubing not a good option?
Fluoropolymer tubing won’t work for most high-pressure applications such as the high-pressure side of HPLC or UHPLC. We offer a comprehensive line of high-pressure tubing in various colors and sizes to accommodate high pressure applications. Stainless steel is very common for HPLC and UHPLC. Stainless steel is the most robust tubing option, and can withstand very high pressures, mostly limited by the fittings used to connect it to the system. One huge benefit to pre-cut stainless steel tubing is the ability to create zero dead volume connections. PEEK tubing is a great polymeric alternative to stainless steel that offers biocompatibility and is chemically inert to most commonly used HPLC solvents. It is also very flexible and can easily be cut to any length. PEEK tubing is available in many sizes with color schemes for easy identification.
"One huge benefit to pre-cut stainless steel tubing is the ability to create zero dead volume connections"
Two additional high pressure tubing options we offer are fused silica and PEEKsil. Fused silica is used for micro-scale analyses such as micro and nano-HPLC, and capillary electrophoresis due to the tight tolerances of fused silica’s inner diameters. PEEKsil is a silica tubing sheathed by PEEK tubing, which is mechanically strong and can be sealed with metal or polymer fittings. PEEKsil offers excellent chemical compatibility and can withstand pressures of up to 10,000 PSI.
How do I determine which tubing goes where in my HPLC system?
Similar to HPLC fittings, different tubing is often used on different parts of an HPLC system. Fittings (or tubing) are classified as high pressure or low pressure and correspond to the areas in the system where the flow path is high or low pressure, respectively. There are various types of fittings used on the low-pressure portions of HPLC systems. High pressure areas are generally considered to be the areas where the flow path exceeds pressures of 6,000 PSI. This includes the area from the outlet of the pump, through the injection valve, and passing through the column. The pressure is created by the resistance of the stationary phase on the mobile phase as it passes through the HPLC column. In the high-pressure area, high pressure tubing (and fittings) is required. Other areas in the system such as from the mobile phase reservoir to the pump inlet, and then from the column to the waste are considered low pressure areas. This is where fluoropolymer tubing, and low-pressure fittings, are used. To connect tubing, flangeless fittings are often used. These can be identified as a nut and ferrule that fits into a flat-bottom port. Other fittings seen within low pressure sides of the system include luer lock adapters, which can connect syringes or other accessories that you would want to be easily added or removed.
Why Are There So Many Options to Choose From?
Choosing appropriate tubing for your HPLC system or other fluidic applications can seem a bit daunting because of how many options exist. Typically, multiple options can work for any given application, but some might be better suited for certain pressures or conditions. Chemical compatibility can be the limiting factor in what tubing you can choose. Thankfully, it’s fairly simple to find solvent compatibility charts for the various tubing and fitting options. If you need any help determining what tubing will work best for a certain application or place in your HPLC system, reach out to our support team.