Which GPC to buy?

[Leticia]

We want to buy a non expensive GPC (used or new) to determine the molecular weight distribution of some styrene-acrylic copolymers we’ll synthesize. Most of my friends have experience with Waters, but they always complain about the software (Millenium or Empower).
Could someone share with me their experience with other brands or specific models including the equipment and software performance so I can make a wiser selection? Thanks

[Noser222]

Millenium/Empower has its advantages for organizing projects and data. If you're just research minded and want to change your methods up as you go then it can be a little tedious to set up instrument methods, method sets, processing methods, sample set methods, etc. Chemstation, at least in its most basic form, is easier to set up because you just make an intstrument method and start running.

[JGK]

Millenium/Empower has its advantages for organizing projects and data. If you're just research minded and want to change your methods up as you go then it can be a little tedious to set up instrument methods, method sets, processing methods, sample set methods, etc. Chemstation, at least in its most basic form, is easier to set up because you just make an instrument method and start running.

The Latest Empower (2) does have a QuickStart interface which allows the user to complete all setups (instrument methods, method sets, processing methods, sample set methods) as well as acquisition and results processing from a single window.

[mbicking]

I have used the ChemStation/GPC systems many times. The 1100/1200 is a very good instrument, and retention time reproduciblity is generally very good. The GPC add-on software generates the numbers you need, but it will not win any awards. It is easy to use, but not intuitive to learn.

If you could find a refurbished 1100 and buy the GPC add-on, you would have a pretty good system. If you are good with software and/or like to dig into learning software, then you can probably figure it out. If you call Agilent for help, they will call me.

[unmgvar]

Leticia,

if your co-polymers will have no degree of cross-linking and will be long "linear" free form then a simple HPLC with an RI or UV or both will be enough for you.
just make sure to have the HPLC suited for very organic solvents such as THF, hexane and other nasty solvents. some parts in the pump and auto-sampler will need to be suited maybe. make sure that they provide a good and easy to use SEC/GPC software suit or reports, EZchrom elite, chemstation, chromeleon or empower are the most comon ones for the job but you aslo can be proposed Clarity.
look a bit at litterature to see how many columns you will need for your separation (up to 3 is norm in SEC for polymers) and make sure that your vendors oven is big enough, otherwise go for a "stand alone" bigger oven on the side.

on the otherhand if you do intend to create cross-links within your polymers in order to change characteristics then i advise you to also purchase a viscometer detector. in that case i know that Viscotek can propose you a nice and easy to use system with their software.

the separation mechanisem in SEC columns is based on the assumption that the bigger the size of a molecule then the bigger its weight. the seaparation is done according to Rh size from there we extrapolate Mw.
for "linear" polymers where we know that the free form of the molecule will be that as close as possible to a sphere and so the assumption will be close enough for accurate results.

in the case of cross-linking then the more you haveof them, the more you will deviate from the assumption and the more you deviate from your real results. a simple system with only RI/UV will not be sufficient.
viscotek software, omnisize will allow you in this case also to calculate the overall branching properties of your polymers.