What can I use as a cap for my mobile phase bottles?

Our choices for mobile phase bottle tops are based primarily on two different products.

The first product is the Hub-Cap Bottle Top, catalog #26541. This is designed to fit a 4-Liter solvent bottle. :

26541solvent-bottle

 

 

The body (also called insert) of the Hub-Cap Top is cap is made of inert PTFE and has three threaded holes. The exterior ring is composed of high density polyethylene and does not usually come in contact with the mobile phase. Threads for all three holes in the body are for ¼-28 fittings, two of them for 1/8 inch OD fitting nuts and the other is for 1/16 inch nuts. However, the intention is really to run 1/8 inch OD tubing through the two larger holes without the use of a fitting nut. Using it this way without a nut creates a slight vent that can be beneficial, since it avoids the creation of a vacuum as solvent is being pumped from the bottle. The 1/16 inch OD hole comes with a PEEK plug that can be removed, if needed for ventilation, or can be replaced with a ¼-28 thread fitting nut if desired.  If needed, catalog numbers 25794 and 25975 can purchased as a nut and ferrule for the 1/8 inch OD holes.  However, at this time, we do not sell nuts and ferrules for 1/16 inch OD ¼-28 fittings, only the PEEK plug that is mentioned.

 

The other product is the Opti-Cap Bottle Top, catalog #27836. This is designed to fit a 1 or 2-Liter GL-45 bottle:

25300

gl-45-bottle

 

 

 

 

 

 

 

 

 

 

 

The body of the Opti-Cap is made of inert PTFE and the exterior ring is made of polypropylene. Similar to the Hub-cap, the body has three holes that are threaded for ¼-28 fittings. Two of them are for 1/8 inch OD fitting nuts and the other is for 1/16 inch nuts and comes with a PEEK plug installed.  Again, similar to the Hub-Cap Top, the intention is really to run 1/8 inch OD tubing through the two larger holes without the use of a fitting nut when used as for mobile phase. As is the case for the Hub-Cap, catalog numbers 25794 and 25975 can purchased as a nut and ferrule for the 1/8 inch OD holes if needed. Again, we do not sell nuts and ferrules for the 1/6 inch OD hole.

You may notice that we also sell the Eco-cap, catalog number 27834, which is a simplified version of the Opti-Cap. It has three holes like the Opti-cap, but none of the holes are threaded, so it cannot be used with fittings.  A luer-type polypropylene plug is provided for the 1/16 inch hole and the body of the Eco-Cap is composed of a translucent polymer called ETFE.

eco-cap

 

 

What to do you do when you have the wrong type of top for the bottle type that you are using?

Here is where it gets tricky.

If you have an Opti-Cap Bottle top already (see above), but you need to use it with a 4-Liter bottle, what you need is a Hub-Cap Adaptor, catalog #26538:26538

You can purchase the Hub-Cap Adapter with the Opti-Cap Bottle Top together as a kit as catalog # 26540.  I would suggest purchasing this kit if you expect to be using GL-45 bottles most of the time, but you might want to use a 4-Liter bottle occasionally and want to be prepared for either. You can also use the Hub-Cap Adapter with the Eco-Cap, to adapt it for use with 4-Liter bottles, if desired, although it will not produce an air-tight seal.

 

If you have a Hub-Cap Bottle Top already (see above), but you need to use it with a GL-45 bottle, what you need is an Opti-Cap Adaptor, catalog #27197:27197

You can purchase the Opti-Cap Adapter with the Hub-Cap Bottle Top together as a kit as catalog #26551.  I would suggest purchasing this kit if you expect to be using 4-Liter bottles most of the time, but you might want to use a GL-45 bottle occasionally and want to be prepared for either.

I hope you have found this informative.

Thank you for reading.

Be sure to also check out our video on this topic “Capping your LC Solvent Bottles”.

 

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