NOX

[wheeltops]

I've been asked a couple of times recently about NOX analysis. What is the best way to analyse for NOX?

Should I be looking at a 5AMS; a plot column; a packed column? Is it possible to separate NOX species or is it total NOX? Will a specialist gas analyser be a better option?

I'd appreciate your thoughts.

Cheers

[CE Instruments]

Levels, %, ppm , ppb ?? Balance gas ? Other gases present and at what level ? Do you just need total Nitrogen or to speciate stable NOX ?

[wheeltops]

Levels, %, ppm , ppb ?? Balance gas ? Other gases present and at what level ? Do you just need total Nitrogen or to speciate stable NOX ?

Sorry, it was a bit vague.
Levels? ppm
Balance gas? So far Air or Argon or N2
Do I need total nitrogen or NOX species - well, as I said I don't know what's possible or what level of derivitisation is necessary to separate NOX species. Is it reasonable to attempt by GC or sensible to splash out on a commercially available NOX gas analyser?

Most PLOT column manufacturers are keen to point out their columns will separate N2 from permanent gasses and light hydrocarbon mixtures but tend to waffle a bit when the question of specific NOX components are raised. I've heard 5 angstrom molecular sieve columns will do a similar job but again, details regarding NOX are hazy.

So, any ideas?

[AICMM]

wheeltops,

Both NO and NO2 have IP's less than 10 e.v so they are amenable to PID or AID. I have chromatograms of NO buried in my file cabinet that I can send you using AID but I am not sure of the column used. It was low ppb work. Problem is getting good separation of CO from NO. I did not do the work, ABB did the work. If you want to post your e-mail I can send you the chromatograms.

Unfortunately, do not have any work on NO2 but I should think it would be detectable. Then, how to chromatograph it??

Best regards.

[CE Instruments]

Looked through my info. and I do not have any specifics for NOx separation. However GC should be the method of choice for analysis, at ppm levels you will need a special detector Helium Ionisation or possibly PID (we supply both in UK) You will not need derivatisation. Do you have a GC that is equpped for this analysis and just need a column or a solution for your application ?

[GasMan]

Here is a quote from page 96 of the book "The Analysis of Gases by Chromatography" by C.J.Cowper and A.J.DeRose

"Other, non-chromatographic, methods are available for measuring NO and NO2, such as chemiluminescence method (Allen, Billingsley and Shaw, 1974) and the prefered tactic would be to use one of those methods and to restrict chromatography to the measurement of N2 and N2O."

I have not seen a 'robust' method for the GC analysis of NO2.

Gasman

[wheeltops]

Well thanks for the replies, it's becoming clear that NOX analysis is a specialist field, the finer details of which are being held close to artisans' chests.

In answer to your question about equipment - I'm tooled up with GC/FID/ECD/MS with S/SL,PTV or headspace inlets. Some years ago I carried out some work with Sulphur gasses on plot columns and I was hoping someone might have a similar solution based on GC/MS using a plot or mol/sieve column.

It just sounds like it might be a bit of fun but unless I can sketch in the preliminary details I'm unlikely to be offered the development work.