CLND ANTEK 8060

[AndreasHahn]

Hi there,

at the moment I carry out a placement for my study.
The company I work at has recently bought this Nitrogen detector.
They use it to detect an amine impurity in an agent.
A chromatographic method is already established. MeOH/H20/TFA (7:3+0,1%) as mobile phase and we use a narrow bore column with a flow of 250µl/min.
(I should not change it, but if necessary I can alter it a little)

It is my job to optimise the settings of the detector to get a better variation coefficient and LOD/LOQ.

I have seen, that some of you have been working with such a detector already. Could you please tell me in short the do´s and don´t´s , as the manual is not of much use for me.
(especially what has to be untried if I don´t want to destroy the detector)

I know that the ozone (oxygen flow) is to be left as it is. (25mL/min)

Thanks for any advice.

Andi

[Kostas Petritis]

Your mobile phase is just fine for this detector.

The main problem with this detector is that is too sensitive in nitrogen so any HPLC or column that has been used somekind of nitrogen containing solvent or additive will give some background noise (this is more true for the HPLC equipment than the column). Needless to say that the use of any solvents or additives which have been contaminated with nitrogen containing compounds and you get a very noisy base line.

So if you have a new column and a new HPLC that would help (some people dedicate HPLC's and columns for that detector).

Another point to check is your spray and normally you shouldn't be accumulating any water in the entry of the pyrolisis chamber.

Finally, lack of pump pulsation always help with these types of detectors...

I wouldn't really change any of the settings of the detector (just what is recommended by the manufacturer)...

PS: You might experience wider peaks than other detectors due to the long tubes required for the mobile phase evaporation...

[AndreasHahn]

Dear Mr. Petritis,

Thank you for the advice.
The company dedicated a whole HPLC System to the CLND-Detector. So it should never have seen any nitrogen containing mobile phase before.
Pump pulsation shouldn´t be to bad, because we use a system with two pumps and mixing in the high pressure system. (I don´t know the correct english expressions, so please excuse me)

I have read your article in the LC-GC-Europe (Juli 2001), there you describe the oxygen setting as 202ml/min and argon 99ml/min.
Why did you use these settings? (I know that it has to be enough O2 to burn the organic phase totally, but why does one reduce the max. of 250?)

If I interpreted the manual right, I could go down with my settings to 209 ml/min O2 and 91ml/min helium.
Coking should not occur. (or is the water part of any interest?)
Anyway does it make sense at all to lower the oxygen flow?.

The long tubes explain the wide peaks.
But I have still got quite a lot background noise and no idea how to reduce it.

I hope you don´t mind the many questions.

Thanks a lot,
Andi

[Kostas Petritis]

Andi,

Antek modifies time to time their instruments so the values that you have might be the updated ones. I used the instrument for about 3 months as we had it as a loan item. At that time, Jean Francois Borny who was a specialist on the CLND (he used to work for the Antek until it was bought by another company etc...) had set it up and assign the values of Oxygen and Argon.

I do not think that they should play a significant role on the background that you observe... The background might come from TFA (are you using the 1 mL TFA or just from the bottle?). You could check the TFA quality by injecting some or by just using methanol:water without the TFA. I assume also that during the set up of the HPLC you didn't use ACN in order to start up the pump (people like to use ACN for it's low viscocity). If yes, I would advice you to clean the check valves... Also if the column that you are using had been used in the past with triethylamine or tetralkyl ammonium, it might still bleading a little bit of these compounds.

So I would start by taking out the column, cleaning the HPLC system (just flash it from the TFA) with methanol:water and letting it overnight at low flow rate. If the background is down, try to inject the TFA (a 20% solution should be enough), then try to add the column and pump the methanol:water through it. Depending on the results you can make the necessary changes.

Let us know if it works or not... if not we can think maybe of something else...

[AndreasHahn]

With some other things it was the TFA which was responsible. Thanks for the hints. And max. sensitivity now is 0,3 ppm N for the component. I think it can´t get any better.