Chromatography Forum

Hello all.

I am in the process of setting up my lab before delivery of an ELSD. We already have a nitrogen generator, but it is only a low pressure model (up to 3 bar only) and the information I have seen tends to suggest higher pressures are required. Unfortunately, information on ELSD operation seems to be a secret and all the literature I have seen is decidely vague.

Can anyone confirm this? I would like to know if I could get by using 2 to 3 bar nitrogen and save myself having to get another generator.

Hi,

We'd need a little more information on what make and model of ELSD your getting.

Regards,
Bull76

It's an Acquity UPLC ELSD. Manual says 4.5 to 6.9 bar Nitrogen and I am wondering if this is an absolute requirement or not.

Hi,

4.9 to 6.5 BAR is equivalent to 65 to 90 PSI. This is what the input supply to the Detector has to be. The detector has an pneumatic bench which regulates down the N2 to the Nebuiliser. Nebuiliser usually operates around 25 to 40psi.
Here's the thing, if you know what your Nebuiliser pressure is going to be you could get away with the supply pressure been 10PSI higher than that.

So unless your N2 generator can output the required pressure then you need to get one that does. Also, the vendor will only validate the detector and results if there installation requirements are met. This must have been stated to you.

Regards.
bull76

The vendor has not given any information regarding validation as yet. I am preparing the site in advance of delivery and wanted to get an idea of what is actually possible with my current N2 generator and then decide weather to upgrade or not. It seems an upgrade would be the sensible thing to do as I don't want to be trying to 'get away' with anything!

Many thanks for the info - much appreciated and very informative.

Hi,

Contact Waters sales rep or service department. They should have given you the operators guide, they should also point you in the right direction for a method. Are Waters going to install and qualify the system?
An upgraded N2 generator would be a wise decission. Have been doing some work on the ELSD 2424 very similiar to the Acquity ELSD. The N2 pressure must be withing that range also you need a vacuum source for the Rear exhaust, located as close as possible to the detector roughly 24inches away.
You should get some form of familiarisation training to.

Regards,
Bull76

As has been said before...

If the spec is: "Manual says 4.5 to 6.9 bar Nitrogen", then that is what you should use. ELSD's in general require a large volume of gas to function. Most small Nitrogen generators are not up to the task. Make sure you have an adequate supply of gas from which you can regulate the flow to the nebulizer and drift tube. Mobile phases with high boiling point liquids (i.e. water) require a great deal of heat and gas to vaporize.