Buying new HPLC: Isocratic or quaternary pump

[88TSodium]

Hi all... I'm newbie in this forum.
My lab is going to buy a HPLC. No one in lab has experience with HPLC.
The application is for separation of saccharide in samples e.g. glucose, fructose, maltose, maltotriose, higher saccharide, sugar alcohol. Thus, the detector will be Refractive Index Detector (RID).
What I know is, gradient elution can't be used in pair with RID so isocratic pump is enough for this application.

If there is enough budget to buy quaternary, which one is better? buy quaternary but use mostly for isocratic elution or just buy the isocratic pump?

Please help to give comment from the hardware's side e.g. the maintenance (which one is more difficult to maintain) or any negative impact to the quaternary pump because of continuous use at isocratic mode.

Thank you very much.

[mattmullaney]

Hi 88TSodium,

I'd go with the quaternary gradient pump for the sole reason that it would give you flexibility for the future. Only if you know that you'll Never need to use gradient HPLC, then go with the isocratic pump.

There will be more to maintain with the gradient pump in terms of seals and the gradient proportioning valve than with the isocratic pump, but that maintenance isn't so much more difficult. You might want to use different channels to deliver the mobile phase, and you'll have to keep all four lines wet for the degasser to function at its best with the quaternary pump, too. I don't think that there'd be "negative impact" to the gradient pump to use in isocratic mode in an overall sense...just giving each line time to work seems a good idea to me.

Please see what you think and thank you.

[bigdawg]

Why not just get a binary pump? I think they are the best compromise between robustness and versatility and if given a option, I'll use them over quarternary pumps due to ease of maintenance and cheaper spare parts.

[mattmullaney]

Bigdawg's got a point...the binary system allows for gradient capability (if needed in the future) as well as "two" pumps you (88TSodium) could use for isocratic work. And, no gradient proportioning valve. The binary pump may cost more at the initial purchase, down the road they are less expensive to maintain.

88TSodium, please see what you think.

[88TSodium]

Yes, I once think about the binary pump but one of the supplier mention a concern about pressure (if i'm not mistaken,because i heard this from my colleague). For operation in isocratoc mode, quaternary system is better than binary. If the system is quaternary, the pressure will be divided into 4 so the column won't receive too much pressure. But with binary, the chances of overpressure at the column is bigger. That's what i understand and i might wrong.
Then, i did check one of the system offered to us, Agilent1260. The manual for quaternary and isocratic comes in a same manual and separate manual for binary. So a thought came to mind that quaternary is more suitable for operation in isocratic mode.

So, for the hardware binary is more expensive than quaternary? How come? Quaternary sounds more modern.

[mattmullaney]

Hi Again, 88TSodium,

Binary Pumping systems use two pumps, while Quaternary Pumping systems use one pump and a gradient proportioning valve. So, if one uses a Binary Pumping system, two solvents are mixing at high pressure (each pump meters separate flows to mix together), so sometimes Binary Pumping systems are called high pressure mixing. And if one uses a Quaternary Pumping system, the gradient proportioning valve meters the volume drawn from multiple eluent containers using one pump, and this happens at nearly ambient pressure...sometimes Quaternary Pumping systems are called Low Pressure Mixing systems for this reason.

Anyway...for both kinds of Pump systems, flow passes through a column...resulting in a high backpressure. There's no advantage to the backpressure generated by flowing through the column in either type of pump system.

And...if you have a Binary Pumping system under isocratic conditions, one could pre-mix the eluent...no high pressure mixing needed. Only one pump is used...if that pump goes bad, then you could still run using the other pump, if you wanted to.

I'd say, for these "pressure criteria", there's no particular advantage for the Binary vs. the Quaternary Pumping system.

Binary Pumps cost more simply because they use two pumps...Quaternary systems use only one pump and a gradient proportioning valve.

Let's see what others have to say.

[Multidimensional]

Quat pump would be superior to binary for most applications. Both need degassing for optimum operation. Quat pump has big advantage that it will have random access to 4 solvents, vs 2 for binary. True random access to more liquids means you can easily program to use different mobile phases AND different wash and equil solutions for proper shut down. Binary pump also has more parts which means more expense to maintain.

If you have the money, get the QUAT pump (not a binary).

[lmh]

gradient proportioning valves are a liability though! Of the bits that go wrong most commonly on pumps, check valves are probably the most frequent, but they're fairly easy to diagnose and replace. Gradient proportioning valves are hard to diagnose without doing a full gradient test (takes hours), and cost a lot to fix. Unless I had significant intentions to run a 3-component gradient, I'd personally prefer binary.

[Consumer Products Guy]

I've got experience with both binary and quaternary pump systems (both Agilent).

I vote for the quaternary system, and just bypass the multichannel mixing valve and route directly into the pump head. So that makes it an "isocratic" system, but the new MCGV and everything associated will already be there, and without wear.

[Himar]

I feel bad that OP is getting conflicting answers . Assuming they will pre-mix for both iso and binary I would go with Binary because, if pump head A is down and you don't have time to maintain, you can switch to pump head B and continue with your samples.

But realistically, if the pumps have the ability to mix, then a person is less likely to pre-mix. In that case you will have twice the amount of maintenance with the binary pump, as far as the pump heads go.

I guess the original question is quat vs. iso, that all depends on whether you think the opportunity will ever arise to run a gradient in the future. If the answer is yes, or I don't know, I would choose the quat pump.

[lmh]

I also feel bad that the original poster is getting conflicting views, but happily this probably means that quaternary and binary systems are both pretty good nowadays, and there is no really bad answer. There is definitely a good answer that if you have spare cash, it's good to have a system that can pump a gradient if you think you ever might need one.

Remember, if you go back to upgrade an existing system, you can really only get a quote from the existing manufacturer, which means you're paying list-prices with little hope of a discount. When you're buying a new system, there is competition with other manufacturers, and the prices drop dramatically. Sad, but true.

On using the pump to make your solvent mix, or doing it yourself: there are arguments both ways. If you put your own mix on, then you won't have things growing in the aqueous phase. Your mix doesn't depend on whether the pump is working correctly. On the other hand, it can evaporate unevenly, meaning that it gradually changes its % organic. If you pump it from pure components, this never happens. If you're doing a gradient, of course, there are other reasons to pre-mix the solvents.

[88TSodium]

Hi all,

First thanks for the opinions.

Finally, we decided to choose the quaternary, for future applications which might need gradient elution.

Once again, thanks.