Chromatography Forum

I did try and search first to see if there were already answers to my questions, but I didn't have a lot of luck.

1) what are the common problems experienced by CAD users. I'm brand new to this form of detection, although I do understand it's similarity to ELSD.

2) how important is the nebulizer temperature? What would I see if a run was ececuted at 25°C and then at 35°C (max)? Also, why is the max only 35°C? You would think that a higher temp max would help the evaporation process, but again I'm new to this.

3) Does this detection technique handle large chain (> 10000 m.w.) molecules well or can they be problematic.

Let's start there.

Thank you

So does anybody use this detector?

Given that it's a proprietary (sole-source) technology, your best source of answers would probably be the manufacturer's (Thermo) tech support.

Hi Charles,

If it is the Thermo/Dionex Corona CAD you have then let me know. I can then put you in touch with our CAD expert.

Thanks

It is. I would appreciate the hookup.

Can I just ask where abouts you are? UK? US? Europe?

Flooding of the detector can occur. Always have gas flow on during, before, and after mobile phase is put through the detector. Emptying the waste carbouy can cause an increase in the baseline noise. The nebulizer temp. is only supposed to matter if you are running THF/water mobile phases, as freezing of the nebulizer can occur. Ghost peaks from things like soap on glassware and vial septa can occur and are annoying. I never used it to analyze anything with a MW >10000, but I'm under the impression that it should work fine. Detector response isn't necessarily linear. I never worked with an ELSD, but I think I would much prefer the CADover it from what I've read.

Can I just ask where abouts you are? UK? US? Europe?

Sorry about the Delay. I'm in the US. St. Louis, Missouri to be more specific.

Flooding of the detector can occur. Always have gas flow on during, before, and after mobile phase is put through the detector. Emptying the waste carbouy can cause an increase in the baseline noise.

The only time the flow gets turned off is during waste removal.

The nebulizer temp. is only supposed to matter if you are running THF/water mobile phases, as freezing of the nebulizer can occur.

We have Mobile phases of 0.1% TFA in water and 0.1% TFA in Acetonitrile with a starting point of 5% Organic ramping to 100% over 8 min. Don't think there is any issue with that Mobile Phase and freezing. My guess is that baseline would be chaotic if that were happening.

Are there any chances of residue buildup on the nebulizer tip that could lead to bad RSD numbers. We have run in to this scenario a few times where the first and sometimes second consecutive injections are low, but climbing. It had gotten so bad that we were having to run seven standard injections in order to get a reproducible 5-rep.

Personally I think its a carryover issue, but since I'm so new to this detector, I'm trying to make sure its not the detector before I carry on.

Hi Charles,

If it is the Thermo/Dionex Corona CAD you have then let me know. I can then put you in touch with our CAD expert.

Thanks

Hi Charles,

If you care to contact me directly I may be able to help. I have worked as a specialist with the detector from its introduction.

norman.ramsey@thermofisher.com


Norman

Can I just ask where abouts you are? UK? US? Europe?

Sorry about the Delay. I'm in the US. St. Louis, Missouri to be more specific.

have you got a phone number and I will call you.

norman.ramsey@thermofisher.com