yellow seals normal phase / black seals reverse phase

I understand.

But the question remains open. If the yellow seals with ceramic pistons maybe work how normal phase so how reverse phase then why do need

black seals and saphir pistons? in very deed the yellow seals are universal. 

jhagel is correct, do not change PE (Yellow) to PTFE (black) seals in round headed pumps (1290 Infinity and Infinity II as well as G7014C).

Both seal types have benefits and downsides:

While the black seals are generally better when using them with reverse phase applications they can easily disturb the chromatography when used with nonpolar solvents like Hexane. They are not suitable for applications running higher than 600 bar but these seals work better with Sapphire Pistons. 

The PE seals are more universal as they are working at higher pressures and with all solvents, but need special attention, like a running seal wash and buffer precipitation can lead to earlier fails of the seals.

Azrael When designing the pumps we had all of these and more factors in mind to give the pump heads the best performance with highest possible robustness. Changing to PE seals in the 1260 pumps is only recommended when using nonpolar solvents but is not needed in 1290 pumps.

Hi,

This is interesting. The manual for the 1260 Isocratic pump (both Infinity I and Infinity II versions) state that the PE seals have a more limited pressure range (up to 200 Bar) is this because they are being used with sapphire pistons in this case?. Also if we are using 1260 pumps isocratically with water or buffer solutions it seems that we should be using the black PTFE seals - in the past I thought I'd been told to use the PE seals in the case, but it looks like this is incorrect? 

Many Thanks,

Jenny

Hi jens, There are many reasons why we recommend the 200 bar limit for PE seals in 1260 pumps when used with nonpolar solvents, one of them is the piston. I would always use the black PTFE seals in the 1260 pumps unless nonpolar solvents are used, so in your case the black ones should work fine.

But please don't get me wrong, the 1260 pumps will work reliably with both seal types, it is the application which determines which seal to use.  

By experience, we usually prefer yellow seals and we use them for normal as reversed phase as well

tobknust Why then use sapphire pistons if there are ceramic pistons? I'm interested. I ask you to understand me correctly, but superficial answers do not satisfy me. You can also use a ceramic piston with a polyethylene seal in many solutions. Are ceramic pistons expensive?