Dear chromatographers, I have an ionic chromatographic system DIONEX 600 and I wish to measure the mono, di and triethanolamine. Does anyone have the experience of this measurement?
DIONEX developed an analytical method with the chromatographic Dionex column CS11 (method DIONEX 138). I tried this method without sucess. I'm looking for someone who uses this method with sucess to help me to apply it.
I would welcome any replies and I would be very greateful for your help.

Best wishes

What levels are you looking at? At my company, we use GC for these three.

These amines are easily determined using a Metrohm Ion Chromatograph, non-suppressed, with a Partisil SCX column, Eluent is 5mmol sodium dihydrogen phosphate pH =2.5 (glacial acetic acid) flow 2.0ml/min injection 10ul volumne. RT for Na 4.8mins; mono-ethanolamine 10mins, di-ethanolamine 14mins, triethanolamine 20mins. Metrohm do a very simple inexpensive IC system. includes the software.
See Metrohm web site Metrohm.com and look at application notes C-7
good luck Ed Farmer

There are a number of options for tackling this analysis. In the first place, there are two analytical systems that will work if you are interested in trying an ion pair separation. 2 mM octane sulfonic acid with 100% aqueous eluent on a macroporous polymeric reversed phase column will allow the separation you request. The caveat is that in this case (as in the method suggested by Mr. Farmer above) is that divalent cations will not elute under these conditions. If you are analyzing a sample where you know there won't be any calcium or magnesium present, this may not be an issue. However, typically real samples do contain both of these ions. In this case, you'll need to regenerate the column periodically to elute these strongly held cations. An alternative method is to use perfluoropentanoic acid. Again, use 2mM acid with 100% aqueous eluent on a macroporous polymeric reversed phase column. This eluent will allow the elution of divalent cations. The other option is to use cation exchange. Two weak acid phases can be used for this application: the IonPac CS15 and CS16 columns from Dionex. The applications are described in the column manuals. Both involve hydronium gradients although the separations could probably be accomplished via a step change. If you are interested in the details please contact me directly via e-mail.

Chris Pohl is correct. Cations can stick to the column ...though in reality they elute so slowly off the column that you would never see them ...the baseline still remains flat ... check it out. Anyway it will depend on your relative concentration of Ethanolamine. If you are very worried, the simple way to get rid of the divalent cations, if present in sample more than the ethanolamine, is to periodically inject 100ul of 100mM H2SO4 on to your column about every 20 or so samples. This will keeps the column clean of any divalent cations. The chromatography system is kept very simple,(application is isocratic) with no loss of performance and that it is extremely low cost to buy + run. No gradients required either. I forgot to mention that the Metrohm system does not require the use of chemical suppressors, whereas with the two methods from Dionex (see above) the use of chemical suppressors is a must. These are about the same cost as an analytical column. Also, please note the use of expensive, unstable eleunts are required with the Dionex system .... your choice. Pls e-mail if you have any querries.

Actually it is fairly easy to obtain an analysis of the monovalent, divalent, and ethanolamines in a single isocratic analysis. With respect to the posts above, no special conditions are necessary to elute the divalent metals from the column. In fact, this is easily accomplished by using a silica-based cation column (Metrohm Cation 2). For a faster analysis of the divalent cations, PDCA may added to the eluent. However, it is also possible to accomplish this with only a mineral acid eluent (i.e. nitric acid), but the divalents will elute at a later time. In both cases, the divalent metals may be easily quantitated with the ethanolamines and monovalent ions and no coelutions.

Please contact me if you have any questions or need additional information.

Get out your hip boots. The BS is getting pretty deep in here. Mr. Farmer's message above is mostly nonsense. First of all, when operating under conditions where K' values are essentially infinite, one doesn't expect to see a wandering baseline as suggested by Mr. Farmer. The adverse consequences of operating under conditions where some analytes never elute is progressive loss in capacity and not a wandering baseline (retention times will drift progressively shorter: check it out Mr. Farmer).

Second, it is utter nonsense to claim that no gradient is needed when not all analytes are being eluted. That is precisely why a gradient is required in many applications. The real reason Mr. Farmer suggests that no suppressor is needed is that no suppressor is available from Metrohm. The fact is, Metrohm does not sell a cation suppressor. They steadfastly stick to the nonsense that nonsuppressed is somehow better because the slope of the calibration plot is slightly steeper when a suppressor is not being used. While this fact does allow them to legitimately make the claim that the technique is more sensitive without a suppressor (since the definition of sensitivity is based solely on the calibration slope and does not take into consideration relative system noise), the fact is that without a suppressor the noise is typically 10-50 times greater while the signal is less than two times greater. Consequently, the suppressor yields typically 5-25 times lower detection limits than a system without a suppressor.

Third, one of the chief benefits of a suppressor is that it allows the use of gradients. Mr. Farmer's argument against gradients and suppressors would be like a GC instrument manufacturer with an oven only capable of isothermal operation claiming that their instrument was better because it didn't require the use of temperature programming! What nonsense! Imagine anyone buying this argument! Of course most people prefer to operate under isocratic conditions. But the freedom to utilize gradients when necessary greatly improves the flexibility of analysis. Suppressors are requirement for useful gradients. You'll never hear that from Metrohm because they don't have a suppressor for cation applications. Furthermore, the suppressor enables the use of much more concentrated eluents and higher capacity stationery phases. This combination greatly increases analytical dynamic range, enabling the injection of relatively concentrated samples without overloading the column or the eluent. Without a suppressor, it is necessary to stick with fairly dilute eluents and relatively low capacity columns in order to maintain background conductivity at a low enough level to have a decent background noise. This substantially limits the flexibility of the analytical system.

Fourth, one of the methods I mentioned will work under isocratic conditions (the ion pair method using perfluoropentanoic acid) with elution of all components. You'll notice in my original message I didn't make any mention of suppressors. I was trying to stay well clear of the commercial BS prevalent in both the Mr. Farmer's messages. The fact is this method could be used either with or without a suppressor. In my opinion, superior performance would generally be observed with a suppressor but the application could be performed successfully either with a suppressor or without one.

Fifth, Mr. Farmer's statement that: "expensive, unstable eleunts are required with the Dionex system" is untrue. There is nothing about the Dionex system that requires eluents that are expensive or unstable. For example, eluent system typically used with the CS15 column is methane sulfonic acid. This eluent is stable for years and is quite economical at the low mM concentration level being used in the application in question . Furthermore, sulfuric acid can be freely substituted in this application. Surely one wouldn't consider sulfuric acid expensive or unstable, would one? Again, nonsense!

Beware of those who find it necessary to utilize deception as a marketing strategy!

No BS. It works well.
I let the user decide if they want to purchase a space rocket to go and do the shopping.
thanks

Mr. Farmer,

I read with interest your latest posting. Your rocket analogy is interesting. I am certainly not trying to intimidate you but rather to encourage you to follow normal common sense practices appropriate for this forum. Apparently my previous posting was too oblique for you. Let me succinctly restate the issues:

1). Please read the question and answer the question being posed. While it is appropriate to add additional commentary on other aspects not part of the original question, your answer should still be formulated in the context of the original question. Although you indicate that you accidentally posted an answer unrelated to the question, the majority of your postings have this characteristic! Perhaps you should try a little harder.

2). This forum should not be used as a basis for a sales pitch. It is inappropriate to incorporate information such as: model numbers of instrumentation (unless this is somehow of critical relevance to the discussion), prices, commentary on the "inexpensive" nature of the equipment, etc. The intent of this forum is to freely and openly discussed chromatography questions. This forum is not intended to be used as a means of free advertising! I doubt the readers of this forum will hold Metrohm in a positive light if you continue this egregious practice.

Chris Pohl

I am a user of Dionex DX600 equipment. Like the user above, we had terrible problems setting up the DX-600 for amines. We have had little or no help from your Dionex representative. The suppressors kept on failing. The warranty on the suppressor is only valid for three months. Their only advice has been to replace the suppressor. We now use a Metrohm conductivity detector in the DX-600 system and run the chromatography non-suppressed. It works great now. The pH of the eluent is acidic through the whole system. WE DO NOT GET HEAVY METALS FALLING OUT OF SOLUTION IN THE SUPPRESSOR.

To anonymous above:

Can you tell me more about the operating condition you were using with your suppressor? We routinely observe excellent suppressor life in this application. We recently completed a long-term study in our lab with the currently shipping version of this product and observed no loss in performance after 12 months of continuous operation. Perhaps you have been using excessive current settings. Its generally best to use the minimum practical current when working with solvent based eluent systems.

We operate a DX 500 system with CS16 column for the above separation and operate without any down time. Our Ultra suppressor is operated at 100 mA.

I forgot to add in the previous message, unlike the earlier message we are happy with the performance of our DX system.

Is there any method to estimate the related impurities by Gas chromatography FID for triethanol amine?

To analyse Triethanolamine by GC I recommend to make a silylation with Trifluoro-N-methyl-(trimethylsilyl)acetamide ( MSTFA ): mix 0.8 ml sample with 0.4 ml MSTFA in a vial and temperature at 60°C for 45 minutes. GC-analysis is possible with Methylsilicon or Phenyl-Methylsilicon - column.