Number of pumps used in binary and quatenary

[uzman]

Hi lmh,

I also strongly recommend applying some backpressure to the pump , it will certainly help to stabilize pump.
An explanation to the backpressure vs gradient precision may be as follows , as the backpressure increases ,the checkvalve on the pump head seals more ,no backflow to the proportioning valve and the flow will be stable.
At zero backpressure , the checkvalve cannot seal properly and some solvent leaks to proportioning valve ( now backpressure applied to proportioning valve ) and changes the solvent percentage in the suction tube.

I have seen some checkvalves which include springs inside pressing the rubby ball , in order to help it close at near zero backpressure. These checkvalves can be found on some old Waters pumps.

[unmgvar]

lmh, the proportioning valve is only part of the creation of the solvent mixture.
like i said the solvent until the mixer are almost non mixed.
the best picture to describe it would be:
thing as each valve opens, a sausage of a certain size goes into the pump and is pushed by the pump, so you have sausages of different kind going one after the other, it could be water80%, acn20%, water80%
, acn20%....
then they reach the blender/mixer, and then the solution becomes 80-20% water-ACN sausage.
like anything else the mixer is dependant on other things to work well. these things are the flow and pressure. using chromolith columns for examples you discover that mixing is not the same. above 2-3ml/min mixing is not efficient anymore in most analytical system- this for example is the reason many doing semi-prep at 4-5 ml/min on some applications do not get the same results has they had in the analytical scale
using TFA you discover that mixing is different between systems depending on the volume of the mixer.
low pressures also have an effect because the pump are designed to work with several bars, generally more then 10-15 bars.

[Arif Mahbub]

hy everybody

i know that in binary gradient system there are two no. of pumps which can mix two eluents
but i dont know that in a Quaternary system why a single pump used and how it can mix four eluents.
can anyone tell me about that........
thnx

Muhammad Afzal

Hi!

In some Quaternary system there are four channels from four bottles and they mix the eluents before it enters the pump that is mixup is done before entering the pump. Another case is four pumps are used for four eluents.

Arif

[lmh]

uzman, thanks, your explanation of the pressure-dependence makes sense to me.

[ljc]

You can get the spring-loaded outlet ball valves from ASI that are compatible with Agilent quat and bin (G1311 and G1312) pumps. They work well; if one dies you replace a cartridge insert instead of the entire assy. I don't think there's a "passive" inlet valve on any Agilent pumps, not by design anyway. They all use an active inlet valve (solenoid actuated). Maybe there's an aftermarket passive inlet valve. But, you'd have to leave the active valve connected or the firmware will not let you run the pump at all; it senses the absence of the active inlet at startup.

[Peter Skelton]

The new Infinity series Agilents use passive check valves, the Active Inlet Valve has been done away with

[LCbob]

The new Infinity series Agilents use passive check valves, the Active Inlet Valve has been done away with

Yes and Waters Acquity have done away with passive inlet valves and gone towards the more intelligent ones, it's a mixed up world.