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Prevent precipitation in IC
Posted: Mon Jun 26, 2017 1:17 pm
by dvburt
We’d like to analyze for anions (sulfate, chloride etc) in a natural sample that also has Ca2+, Mg2+, Fe2+. We are worried that the eluent (either KOH or NaHCO3) will cause precipitation (CaCO3, MgCO3, Fe(OH)2) and clog the column. We wonder how to avoid precipitation.
What would be the approach in this case?
Re: Prevent precipitation in IC
Posted: Mon Jun 26, 2017 3:52 pm
by HPLC chemist
Acidify with 0.1 M Ammonium Citrate buffer pH 4.4 (perhaps?).
Re: Prevent precipitation in IC
Posted: Mon Jun 26, 2017 5:16 pm
by mattmullaney
Perhaps you could employ ion-exchange solid-phase extraction on the sample solutions to remove the transition metals (at least)? Dionex InGuard cartridges, maybe in Sodium form?
https://www.thermofisher.com/order/cata ... uct/074036
Please, see what you think and thank you!
Re: Prevent precipitation in IC
Posted: Tue Jun 27, 2017 5:59 am
by Markus Laeubli, Metrohm
So far we have not seen clogged columns due to Mg, Ca, Fe applying hydrogen carbonate, carbonate, hydroxide and their mixtures. We use inline filters in front of the guard column. Iron in the sample is kept back and gives a yellowish color on the filter.
Re: Prevent precipitation in IC
Posted: Tue Jun 27, 2017 5:13 pm
by John Guajardo
Hi dvburt,
I am not sure of your hardware, but if your system includes a Dionex AS-DV autosampler, you could use Dionex Guardcap H or Guardcap Na vial caps to remove cations and transition metals in your samples. I would be glad to send you a sample if you have an AS-DV and would like to try these. Just let me know via email at (
john.guajardo@thermofisher.com).
Dionex Guardcap vial caps product page:
http://www.thermofisher.com/Guardcap
Dionex Guardcap vial caps specification sheet:
https://assets.thermofisher.com/TFS-Ass ... 202-EN.pdf
Re: Prevent precipitation in IC
Posted: Thu Jul 27, 2017 11:37 am
by Khanom
When buffer salts are used in mobile phase/s, be careful that the buffer salts are not allowed to precipitate out of solution and cause the pump parts to stick. Hence when the system is not used for injections, ensure that the buffer solution is always circulated through the pumps at a low flow rate, such as 0.2 ml/minute. If necessary, re-circulate the mobile phase/s. Don’t let the pump lie unused for more than ten minutes, if there are buffer salts within the mobile phase/s.
When you have finished using the buffer, flush the system with 15/85 methanol /water for two hours. When buffers with a very high salt content are used, it is useful to back-flush the pump pistons, please see the pump user manual.