By Anonymous on Monday, May 5, 2003 - 03:16 am:

can anybody tell me which anions another than the fluoride, chloride, nitrite, bromide, nitrate,phosphate and sulphate can be measured out with an ion chromatography with chemical suppression and at which retention time? ( I use 1,8 mmol/l sodium carbonate and 1,7 mmol/l sodium hydrogenocarbonate and an A supp 4 column)

-------------------------------------------------------------------------------------------------------
By readski on Monday, May 5, 2003 - 09:39 am:

Retention times may be specific to your column/ systems but we have done Thiosulfate, Oxalate, Chlorate....

-------------------------------------------------------------------------------------------------------
By Anonymous on Tuesday, May 6, 2003 - 08:05 am:

dear anon,
pls send me your e-mail address and i will send you a lot more information.
The column Met Supp 4 is a general anion column. Column will perform the popular anions and some organic acids e.g acetate, formate, glycolate, propanate, butyrate (isomers of), valerate (isomers of), citrate etc. also other ones like chromate, polyphosphate / ortophospahte / pyrophosphate
also unusual anions possible too like bromate / chlorite / chlorate, but these are probably best perfromed on the Met Supp 5 long column .....
what anions are you particularly interested in?
regards
efarmer@metrohm,co.uk

-------------------------------------------------------------------------------------------------------
By Anonymous on Tuesday, May 27, 2003 - 01:47 pm:

I thought this site was for technical help as opposed to sales info. The Metrohm person will only give you bias opinion.

-------------------------------------------------------------------------------------------------------
By ed farmer on Wednesday, May 28, 2003 - 04:36 pm:

Actually the column in the user's question was about the Met Supp 4 column. This is a Metrohm product. Therefore it makes sense that someone from Metrohm answered this query.
The information given is just tech information.
In what way is it biased ?
What is your problem ?

-------------------------------------------------------------------------------------------------------
By tom jupille on Thursday, July 3, 2003 - 03:20 pm:

Sorry for chiming in late here. The rules regarding "sales info" on the forum are based on common sense:

1. If a "vendor" has a product that solves a problem or answers a question posted on the forum, he is entitled to talk about it. However:

2. If he does, he should clearly identify himself as a manufacturer/supplier/vendor/whatever so as to not mislead readers, and

3. He should also not "bad-mouth" a competitor's product.

Ed Farmer's post complied with all the rules, which makes it a perfectly legitimate post in my book.

-- Tom Jupille

p.s. If anyone wants to know why I get to make the rules, it's because the funding for this site comes out of my budget!

-------------------------------------------------------------------------------------------------------
By Anonymous on Saturday, November 29, 2003 - 06:00 pm:

Can somebody suggest a column and procedure for separation of clorine, florine and sulfate ions in the composition mixture. hPLC or ion-chromatography. I have material with anions in 20-1000 ppm (mixture)

-------------------------------------------------------------------------------------------------------
By Chris Pohl on Monday, December 1, 2003 - 03:15 pm:

Virtually any ion chromatography column designed for anions is suitable these anions. One suggestion is the AS14A column from Dionex. It provides good fluoride resolution from the void, so it works well for determination of fluoride at low levels. The colummn is designed for use with carbonate eluents but is also compatible with hydroxide eluents. More information is available on the Dionex website

-------------------------------------------------------------------------------------------------------
By Anonymous on Wednesday, December 3, 2003 - 09:46 pm:

Thank you Chris
I am borrowing AS14A from my co-worker and going to try it.

-------------------------------------------------------------------------------------------------------
By John Livesey on Wednesday, April 28, 2004 - 03:06 pm:

We need to add another supressor to our 2 detector system. I am looking for other users' experiences with Alltech suppressors, in particular the DS-Plus. We already have a Metrohm, and based on our experience, don't want another (no reply needed from manuf.). We also don't want to buy Dionex, based on other users experiences, and because they left us high & dry by refusing to sell us a column after we bought our system from Metrohm instead of from them (no reply needed from manuf.). I don't intend this to be an IC flamefest, but any info about anyone except Metrohm or Dionex would be appreciated.

-------------------------------------------------------------------------------------------------------
By Anonymous on Saturday, May 1, 2004 - 06:27 am:

what application(s) are you doing ?? recommendations will depend on what you are doing. More information from John Livesey required.
Analytes
Levels
Supporting Matrix etc
Interferences from other analytes ?
What was so bad about the other manufacturers suppressors. Why did they fail?

-------------------------------------------------------------------------------------------------------
By John Livesey on Wednesday, May 5, 2004 - 07:53 am:

To "Anonymous": we are doing the "usual" anions (F, Cl, NO3, PO4, SO4) in everything from drinking water to sewage lagoons. Levels are 0.02-1500 mg/L, depending on the analyte. The only suppressor we have is the Metrohm, (it has not failed, and we will continue to use it) -- what I don't like about it is that it is actually 3 suppressors which are switched in & out of the eluent stream. When something goes wrong with a run (eg shutdown due to leak,power glitch etc) you have to re-equilibrate all three before resuming analyses, to ensure that all 3 are "the same". This may seem like a small thing, but in day to day use, it is a pain, and a simpler design would be appreciated. There are 2 regenerant reservoirs which need filling daily. Another problem is the inability to use 2mm columns when using this design -- too much peak broadening.

-------------------------------------------------------------------------------------------------------
By Anonymous on Thursday, May 6, 2004 - 06:53 am:

Your anions are not unusual. I have used the Metrohm suppressor with great success for these standard anions. It has not failed on me either (8yrs old). As I understand, the suppressor capacity is about 2 hours for a typical carbonate/bicarbonate eluent. Typical chromatogram run time is 10 to 20 mins, so it does not matter if each mini suppressor is not exactly the same capacity, so long as it exceeds the suppressing time of chromatogram, which it always does for these anions. In any case, when you start-up a system, it makes sense to stabilize the whole system. Since you are using conductivity as a detector, it would make great sense to wait for the detector to stabilize too. A small change in temperature leads to a large change in conductivity. So this washing and conditioning the suppressor is time that you would have used /wasted anyway while the detector warms up. If you do not do this, then your base line will not be flat. This applies to any manufacturers’ system.
Using two reservoirs (water and 20 mM approx. sulphuric acid) takes only a minute to make. The acid does not need to be made accurately. I usually add 5 ml of conc. to 1 L of water. It takes only seconds to make. Though if you really wanted a reagent free IC system.
Re 2mm columns. I have had no unnecessary peak broadening using standard IC columns 3mm to 5mm size. Are you sure you have no voids in your system ? Why would you want to use a 2mm column when most columns for IC use 3 to 5 mm columns. Who said that you can not use 2mm columns anyway? Have you tried it? Have you asked Metrohm if you can use a 2mm column?
Surely it is the greater pain to replace at great expense (over $1500each ) an expensive suppressor. I have never needed to replace mine. Metrohm now warranty their suppressor for 10 years. So I can see why they offer this warranty as it is rugged and robust. I used to have a Dionex system and constantly had to replace the suppressor every year. Running the Metrohm suppressor has saved me a lot of money.
I think for your type of samples you should give greater attention to the type of column that you use, since your samples will cause the column to deteriorate more quickly than the suppressor.
Have you tried using the Cetac AN2 Transogenomic column. You can run it with replaceable and cheap guards columns.

-------------------------------------------------------------------------------------------------------
By Anonymous on Thursday, May 6, 2004 - 07:51 am:

Hints to John Livesey.
1. Run the eluent waste through the suppressor washing position. Then you will not need to run water through the washing system. So no water bottle to fill anymore. You will only have to make up the acid solution.
2. You could increase the acid one lire resevoir to a 2.5 litre resevoir and then you only have to change the regen bottle once / month. Not too much bother me thinks.
3. On start-up, step the suppressor every 4 mins. Do this three times in a time program on separate method and the suppresor is fully washed and regenerated in 12 mins which is faster than the detector stablibilty time. Problem solved.
My metrohm suppressor has not failed either. Six yrs and still running.
Why on earth do you want 2mm columns ??? I use the Metrohm Met Supp 4 column. It is great for your anions.

-------------------------------------------------------------------------------------------------------
By John Livesey on Friday, May 7, 2004 - 02:48 pm:

Thanks to the anonymi for some useful comments -- very encouraging that the one we have will last. re 2mm columns, it was our Metrohm distributor who said not to bother. No matter now, because we are using Alltech AllSep A1 -- the problem was always NO3. I wanted taller, thinner peaks so I could use small inject volumes (lots of sulfate here). With the A1 we are using 20uL injects, can measure 0.02ppm NO3 and 1500ppm SO4 in same sample. We had used Met Supp 5 but PO4 & SO4 were not separated well enough in our samples.

-------------------------------------------------------------------------------------------------------
By Anonymous on Tuesday, May 11, 2004 - 06:19 am:

I think (not sure) if you decrease the pH of the eluent(by increasing the ratio and conc of the Hydrogen carbonate of the eluent) then the Phosphate will elute a little faster than the sulphate. It should help to resolve your sulphate and phosphate issue. Detection of Nitrate and Nitrite can be completed by UV detection. The other anions should not interfere. Above is applicable to most IC columns using carbonate/bicarbonate eluents.

-------------------------------------------------------------------------------------------------------
By Vangelis on Wednesday, June 16, 2004 - 01:58 am:

We have been using a DX500 system, for cations and anions and we're now buying a new colunm for organic acids; the IonPac ICE-AS1. On the specifications paper, it's pointed out that as regenerant TBaOH should be used. Does anybody know whether this should be a in-water solution or a in-methanol one?

-------------------------------------------------------------------------------------------------------
By Chris Pohl on Thursday, June 17, 2004 - 11:10 am:

Vangelis,

The aqueous based TBOH should be used.

-------------------------------------------------------------------------------------------------------
By Vangelis on Friday, June 18, 2004 - 12:38 am:

thank you Chris.

there's sth strange i'm observing today for the first time. The eluent that till yesterday evening was giving me a background conductivity of 1.5 ~uS (which was fine as the ideal for the application is 1-3 uS), today gives me 5 uS (with the suppressor on and working). It's the same eluent.. could that be explained somehow?

-------------------------------------------------------------------------------------------------------
By Anonymous on Friday, June 18, 2004 - 05:15 am:

probably CO2 got in and dissolved in the eluent ... increasing the background. Suggest you make some more fresh eluent and keep it vacuum packed, i.e in a bag which calapses on itself ... or over nitrogen / helium.

-------------------------------------------------------------------------------------------------------
By Chris Pohl on Friday, June 18, 2004 - 06:18 pm:

Vangelis,

Are you using a suppressor for ion exclusion? It's not generally recommended that you use a standard anion suppressor (e.g. the ASRS Ultra II) for ion exclusion applications. It will take a long time before such a suppressor reaches equilibrium with the regenerant. The ion exclusion version of the suppressor is assembled with the device components in the tetrabutylammonium ion form so equilibration is fast. Also, I'm not sure what your eluent is but typical background conductivity in the ion exclusion mode are around 30uS, although this certainly depends upon your eluent. What eluent are using?

-------------------------------------------------------------------------------------------------------
By Anonymous on Saturday, June 19, 2004 - 07:00 am:

I am just reading this thead after being out of town for several days. What is anion exclusion. I have heard of ion exchange and ion pairing but not exclusion. Is it similar?

Thanks

-------------------------------------------------------------------------------------------------------
By Chris Pohl on Saturday, June 19, 2004 - 11:45 am:

Ion exclusion is a mode of separation commonly used for separation of organic acids (the corresponding separation mode for organic basis is also possible but rarely practiced). The separation medium is a fully functional strong acid cation-exchange resin in the hydronium form. The mobile phase is generally dilute acid, the specifics of which depends somewhat on the detection mode. Retention is dependent upon the extent of ionization with highly ionized compounds being unretained and neutral compounds having maximum retention time (assuming that there are no other secondary retention mechanisms, an assumption which is rarely true). You could make the argument that this separation technique is named backward since the name refers to the process that impedes retention whereas most separation techniques are named according to the factors responsible for retention. Probably, it should have been called nonionic inclusion chromatography. But, I guess it's too late to talk about changing the name after it's been in use for so many years. The technique has elements which are similar to size exclusion chromatography with a minimum retention for fully ionized compounds (at the total exclusion volume of the column) and a maximum retention for neutral compounds not subject to additional retention mechanisms (the total permeation volume). A number of companies make products for this separation technique including Dionex, Showdex and Bio-Rad. If you're interested in more specifics I'd suggest you peruse their web sites for more information regarding this separation technique.

-------------------------------------------------------------------------------------------------------
By Vangelis on Monday, June 21, 2004 - 12:48 am:

Dear Chris,

no i was still referring to the Cations application, namely, CSRS as a suppressor and the CS12 as a column. For the organic acids application of course we'll acquire the respective suppressor (ICE suppressor) that is suggested by the manufacturing company.

As about the possibility that CO2 was dissolved in the eluent increasing the background conductivity, no, that could not be the case cause the eluent i was referring to was fresh (produced by a stock solution that very morning). Perhaps there has been something wrong with the suppressor performance, which i'm now examning. The background conductivity eventually fell within the expected values, but it was after a rather long time. In other words, it seemed to be rather late in equilibrating. Any possible reasons one come up with for such a matter?

thanks to everybody for their replies.

-------------------------------------------------------------------------------------------------------
By Chris Pohl on Monday, June 21, 2004 - 04:37 pm:

Vangelis,

My mistake! Of course, your problem is a considerably different case. First off, the primary suspect in this case would normally be the tetrabutylammonium hydroxide. What is your source and purity of this reagent? In my experience, you should buy one of the better purity grades from Fluka or Sachem. Two impuities are common: carbonate and tributylamine. Both can cause background problems. Carbonate can take quite a while to clear the suppessor and you will see elevated background in the interim.

-------------------------------------------------------------------------------------------------------
By Vangelis on Friday, June 25, 2004 - 06:38 am:

With a newly produced,reagent solution the problem was faced and the system is working like new, thank you Chris.

-------------------------------------------------------------------------------------------------------
By Anonymous on Wednesday, June 30, 2004 - 02:19 am:

Hello everyone,
I am new to this message board. I have been struggling for
about 3 years now with the following problem: Getting persons
in my lab to use ion chromatography for counterion assays on a
routine basis. We are all primarily reverse-phase HPLC users
(about 90 - 95% of our work) so for the few organic counterions
that are assayed in our lab, people are using ion-pairing by
HPLC-UV. Just recently, I talked to someone who has used
HPLC-ELSD for inorganic counterion analysis (e.g., sodium,
chloride). Although this person has shared with me some of the
disadvantages of ELSD (e.g., narrow linearity range, high
sensitivity so not good for residual ion analysis), it looks like
HPLC-ELSD may be adequate for our counterion assay needs.
We currently have one IC instrument in our lab, and I would like
to make a decision before the end of the year on whether or not
this instrument is needed. Any assistance from persons who
have used both IC and HPLC for ion analysis would be
appreciated.

Regards,
New Viewer