To connect stainless steel, PEEK or PTFE tubing into a compression screw type fitting (a female end fitting), a compression screw and ferrule are required. The compression screw engages the screw thread of the fitting and tightens into it whilst the ferrule locks onto the tubing and deforms to the shape of the internal surface of the fitting to create a high pressure seal.

Compression Screws and ferrules may be made of steel or PEEK (others are not recommended). They may be separate or of a one-peice design and they may need a spanner to tighten or have a knurled ring to allow finger-tightening.

For connections to a Rheodyne valave it is important to use Rheodyne fittings (see under Injection Valves). For most columns we recommend a Valco type nut and ferrule.

Finger tight fittings create their own ferrule lock distance each time they are used and do not need to be cut off. Hence if more than one column is to be used and the pressure is unlikely to exceed 3-4000psi, they are more preferable to steel permanent connections.

Hexagon headed steel compression screws and ferrules
(Max Pressure > 6000psi)
Use these for more permanent connections. They give a high pressure seal and are very strong. They may be re-used but always use a new ferrule when re-using the screw.

Finger-tight fittings (one piece)
(Max pressure ca 3000psi)
These fittings are cheaper to make and to buy, but do not last as long becuase each time they are used the sealing surface is scratched and damaged. Use these for econamy.

Finger-tight fittings (two piece)
(Max pressure ca 4000psi)
These fittings last longer because the ferrule does not rotate (and scuff) when the fitting is tighened. When it eventually does leak, only the ferrule need be replaced.

Click here to see a diagram of a ferrule and ferruel lock distance

For low pressure connections using PTFE tube (1/8" or 1/16") a flange-type fitting may be used. There are two types. In one case a special tool is used to flare the end of the tube and the seal is created by screwing this against the inside of the fitting. The second uses a ferrule the opposite way round to the tube and compression fitting. The ferrule seats right at the end of the tube and creats the same effect. This second type of fitting is what we supply. No special tools are required and they are interchangable with the flared type. They are also available in a range of colours.

These fittings are used for the solvent inlet line into the pump, or to the inline membrane degasser and from that to the gradient contoller or pump. If three or four solvent lines run through a degasser and then on to the gradient controller with a single line from there to the pump, we recommend using different colour fittings for each line to enable it to be followed easily. Our solvent reservoirs are available with matching caps.

Click here for a diagram of the 2 different types of flange fittings

Click here for our selection of Flange Fittings

A column end fitting consists of a compression screw, ferrule, end fitting and frit, designed to fit 1/4" od tube. Unless you pack your own columns, these will only be required as a paracute if you shear off a compression screw in your column end fitting. Even then you only need the end fitting part and it may not fit your column ferrule very well. However if the column has the right endfitting and costs enough be worth a try. If in doubt, call for technical advice before ordering.

Click here for a diagram of a column end fitting

These are used to plug the end of a column when not in use.

See our dedicated page for more ordering information

All particles entering an HPLC system are trapped on the columnif not before. Hence it is strongly recommended to filter samples and eluents before analysis. However an HPLC system has two other protection filters and an optional third.

Solvent Line Inlet Filter
This is a sinter, made of steel or PTFE which fits on the end of the 1/8" PTFE line in the mobile phase reservoir. There are two types. Sintered Steel slip on filters just push inside the end of the tube (be aware that the OD of the filter tube must fit inside the ID of the PTFE tubing). Not all manufacturers filters (especially Waters) fit standard 1/8" tubing. However the steel slip on filters below DO fit the 1/8" PTFE tube listed in the tubing section.

Frits
A frit is the filter that goes inside the column end fitting. It is usually 2u and MUST be smaller than the particle size of the packing material. They are made of sontered steel and are usually flat. For narrow bore columns, please call for technical advise before ordering. For Whatman columns, please order WCS frits.

See our dedicated page for more ordering information.

Inline Optional Solvent Filter

This is a device which is fitted between the injector and column as a last ditch filter.
Advantages: Takes out any crud which would block the frit.
Disadvantages: Can cause cross contamination if particles cane from samples.