Help: HP 1090 with a Waters 410 RI

[dalehramsa]

I had to retire a HP 1047 RI detector as it was unable to heat up to 85C, giving a terrible baseline for carbohydrate analysis. In its place, now, sits a Waters 410 RI detector -- which is presently disconnected from our HP 1090 Series II LC and its 35900E interface. From what I can tell, I should be able to reconfigure our system using analog from the Waters while foregoing instrumental control. I have been having issues setting this up, however. Suggestions?

[Bryan Evans]

85C seems awfully high for LC-RI of carbohydrates. Baseline
fluctuation can occur if there is too much of temperature
differential between outlet of column and RI detector.

Was the column oven set at 85C as well? Was the tubing
short?

[dalehramsa]

Actually, we a run at 80, with the column oven set to 80 as well. We had 3 inches of PEEK separating the column outlet and the detector inlet, which we actually tried insulating.

[Bryan Evans]

Are you using an aminopropyl phase?
Imtakt generally uses 50-60C for NP of saccharides.

Afraid I'm not much use as far as instrument control goes.
Hopefully someone else in here offer some insight.

[dalehramsa]

No, for the time being I'm running isocratic H20 with a phenomenex rezex Pb2+ all the while using up de-ashing cartridges like they're going out of style on a Hitachi L-6200/AS-4000 -- it's a pretty weak setup. We're doing biomass fractionation analysis and some of our samples have a high salt content even after exhaustive workup.

Tell me more about what you've used the Imtatk with aminopropyl for, and if you were using RI ? For 50-60C post-column I'd automatically think ELSD.

[Noser222]

Hmm what I don't get is why you need the RI set to 80. The column yes, but I've run fine leaving the RI set to 30 with ~1 foot of tubing between the column and UV and then another 1 foot between the UV and RI.

If you have ELSD, then you should try the aminopropyl phase; you can neutralize and dilute with aceontitrile.

[Bruce Hamilton]

What exactly is the problem you are seeing?.

I've normally run the RI 410 at 45-50C when feeding it from columns at above 50C, including Biorad Aminex 87H with 0.01M H2SO4. Just use a short length of stainless, and wrap a little insulation around it. I was running it on a 1050 system with a 35900C.

As the flows are usually low, the thermal gradient drops, and the 410 I used had a single input line that is switched from reference to sample flows, so you can just optimise the insulation to get a good baseline.

Please keep having fun,

Bruce Hamilton