How to buy a used HPLC module without getting burned
Agilent 1100 and 1200 modules are the most available used lab instruments on earth. Here is what actually determines whether one is worth buying.
If you spend any time in lab surplus you will notice that a startling share of it is Agilent HPLC. The 1100 and 1200 series were sold in enormous numbers, they lasted, and labs are now cycling off them. That makes them the most available used lab instrument on the planet, and one of the easiest to buy badly.
We have a stack of them on the bench right now. Here is what we check.
An HPLC is a stack, not a box
This is the first thing that trips people up. An Agilent HPLC is not one instrument. It is a tower of separate modules, each of which is its own device with its own serial number and its own failure modes:
| Module | What it does |
|---|---|
| Degasser | Removes dissolved gas from the solvent, so the pump does not cavitate |
| Binary pump | Pushes solvent through the column at high pressure, blending two channels |
| Autosampler | Injects the sample |
| Column thermostat | Holds the column at a stable temperature |
| Detector | Actually measures what comes out |
You can buy these separately, which is exactly why they show up at auction separately. A lab replacing one tired pump keeps the rest of the stack running.
That is good news for a buyer. You are usually not trying to buy a whole system. You are trying to replace the one module that died.
Pumps: the thing to actually test
A binary pump is the module that does the hardest physical work, so it is the module most likely to be tired. It has seals and pistons that wear, and check valves that gum up.
Here is the honest limit of what a non-lab seller can tell you. We can put water through a pump and watch for leaks at low pressure. That tells you the seals are not blown and the pistons move. It does not tell you the pump holds pressure at 400 bar, that the flow is accurate to spec, or that a binary gradient is proportioning correctly. Those need a proper test rig and a calibrated reference.
So when you see a used pump advertised as “tested,” ask what was tested. If the answer is “it powers on,” that is not a test of a pump. If the answer is “it pumps water with no visible leaks,” that is honest and useful, and it is what we say, because it is what we actually did.
Assume you may be into it for a seal kit. Price accordingly, and be pleased if you are not.
Degassers: cheap and quietly important
The degasser is the module people skip, and then their baseline is noisy and they cannot work out why. Dissolved gas comes out of solution when the pressure changes, and the bubbles land in your detector.
They are also usually the cheapest module in the stack. If you are assembling a system from parts, do not economise here.
What kills a module for good
A cracked or seized pump head. Repairable in principle, rarely worth it.
Missing the control software or a licence path. The module is only half the instrument. This is the single biggest source of discount in used lab equipment and we wrote about it separately in the software gate.
Solvent damage from something aggressive left in the flow path. If a lab ran something nasty and did not flush before disposal, the seals and tubing can be shot. You cannot see this in a photograph, which is precisely why the price is what it is.
What to ask a seller
- Does it power on, and does it complete its self test?
- Has anything been through the flow path other than water and common solvents?
- Was it flushed before it was shut down?
- What is the serial number? On Agilent gear this dates the unit and tells you the generation.
A seller who can answer those is a seller who looked at the thing. A seller who cannot is selling you a photograph.
What we do
We power everything on. We run water through every pump and watch for leaks. We say plainly which tests we ran and which we did not, and we price against the tests we did not run rather than pretending they passed.
That is not modesty, it is the only defensible way to sell an instrument you cannot fully qualify. The alternative is to guess in your own favour and let the buyer discover it.