Tubing sleeves for capillaries

For easy minimal dead volume capillary connections

Biotech Fluidics provides a range of different tubing sleeves for connecting various capillary dimensions into standard 10-32 or 6-32 coned port designs, including the MicroTight® and NanoTight™ fitting systems. The sleeves are colour-coded for easy inner diameter identification.

Note that the 1/16” OD sleeves can also be used with the Super Flangeless™ fittings in 1/4-28 flat bottom ports and that the PEEK 1/16” OD sleeves are recommended to use with the SealTight™ fittings when connecting to 10-32 coned ports.

Tubing sleeves in FEP materials are generally rated for lower pressures than PEEK tubing sleeves, but in return they do require less torque to seal, making finger tightening sufficient in most cases. The PEEK tubing sleeves are normally required when stainless-steel fittings are used, to avoid extensive sealing pressure that could potentially damage of the capillary wall.

How to choose and install sleeves?

First select a sleeve material and outer diameter (OD) that match your fitting system and receiving port, and then find a sleeve inner diameter (ID) that match the OD of your capillary tubing while allowing 0.001”–0.002” (25–50 µm) gap between the capillary and the sleeve. Then, slip the sleeve over your capillary flow path tubing, such that your capillary extends all the way through the sleeve, but not beyond the end of the sleeve. Pick the correct fitting that corresponds with your receiving port, slide it over the sleeved capillary and connect as normal.

Why use tubing sleeves?

Because most capillary tubing connections are made into coned receiving ports, where the port is not designed to be used with capillary tubing directly, special care must be used to ensure a good connection. While custom ferrules can help make these connections, they only offer a fixed-length nose — and because most tubing pockets will vary slightly in length, this can lead to leaking or dead volume.

To help save overall expense while maintaining a concentric connection with minimal dead volume, Biotech Fluidics recommends the use of IDEX tubing sleeves. Because sleeves are not permanently attached to a ferrule, they can easily adapt to varying tubing pocket depths. Additionally, because they are manufactured using extruded polymer tubing, you are assured of the concentricity of the resultant connection.

Product details

MicroTight® tubing sleeves (0.025” OD PEEK)

  • Manufactured from PEEK polymer
  • Pressure rated to 4,000 psi (276 bar)
  • Connected using the F-172 MicroFerrule together with P-416BLK MicroTight® female nut to 5/16-24 coned ports

IDEX Health & Science MicroTight® tubing sleeves feature an outer diameter of 0.025” and offer a wide assortment of inner diameters to help facilitate capillary tubing connections with the MicroTight® accessories. Because the sleeves are manufactured from PEEK polymer, they carry an upper temperature threshold of 125 ºC.

NanoTight™ tubing sleeves (1/16” OD FEP)

  • Manufactured from FEP fluoropolymer
  • Pressure rated to 4,000 psi (276 bar)
  • For use with fingertight fittings
  • Not recommended for stainless-steel fittings

NanoTight™ tubing sleeves are manufactured using FEP fluoropolymer and precisely cut to a 1.6” length. A wide assortment of sleeves is available, ensuring the availability of a NanoTight™ sleeve for most applications. Many of the sleeves feature a light colour tint that can help more easily identify the inner diameter for future orders. Because FEP is the base polymer for these sleeves, there is a maximum recommended continuous operating temperature of 50 ºC.

The NanoTight™ sleeves were designed primarily for use with the NanoTight™ fittings and also work well with the Super Flangeless™ fittings for connecting 1/16” OD tubing to flat bottom ports. For connections that will be used with stainless steel fittings or at higher temperatures, we recommend using the PEEK tubing sleeves, found below.

1/16” OD PEEK tubing sleeves

  • For connecting capillary tubing to standard 10-32 ports
  • Pressure rated to 6,000 psi (414 bar)
  • Must be used with wrench tightened nuts
  • Required when using stainless steel fittings

Like the NanoTight™ FEP sleeves above, these PEEK tubing sleeves are designed to be used with 1/16” OD, 10-32 threaded fittings to adapt capillary tubing to standard coned ports. Made of PEEK polymer, these 1.3” long sleeves can be used up to 125 °C and 6,000 psi (414 bar).

These sleeves require a wrench tightened nut to achieve proper sealing and we recommend the F-193 SealTight™ fitting with F-192 slotted dual-grip ferrule. Many researchers also use a stainless-steel nut and ferrule with these sleeves, such as the U-400 and U-401.

1/32” OD FEP tubing sleeves

These 1.6” long sleeves facilitate connecting capillary tubing into ports designed for 1/32” OD tubing. Please refer to the product listing below to select the appropriate sleeve for your capillary OD size. These sleeves can be used at up to 50 ºC and have a pressure rating of 1,750 psi (121 bar).

Recommended fittings to use with the 1/32” OD FEP sleeves:

  • The F-113 ferrule with any two-piece fingertight nut for 10-32 ports
  • The F-126S MicroTight® fitting for 6-32 coned ports

1/32” OD PEEK tubing sleeves

These 1.6” long 1/32” OD PEEK tubing sleeves can be used with any fitting designed for 1/32” OD tubing when smaller tubing must be connected. Select the appropriate sleeve from the product listing for your capillary tubing OD size. The 1/32” OD PEEK tubing sleeves have a maximum recommended temperature of 125 ºC and have a pressure rating of 5,000 psi (345 bar).

Recommended fittings to use with the 1/32” OD PEEK sleeves:

  • The F-113 ferrule with any two-piece fingertight nut for 10-32 ports
  • The F-126S MicroTight® fitting for 6-32 coned ports
  • The F-112 MicroFerrule with P-416BLK MicroTight® female nut


Consult the Periodic Table of Analytical Fittings for a quick overview, the Fittings 101 for guidance and learning, and the IDEX Catalogue for product details, or contact Biotech Fluidics for expert advice.

Periodic table of
analytical fittings

Fittings 101
guide booklet

Complete IDEX

Any questions?

If you have any inquiries about our products and services, we’re here to help.

Phone: +46 300 56 91 80
Email: info@biotechfluidics.com