Hi

I have a ground water sample which contains about 500ppm of calcium ion. The calcium ion will form a calcium complex with my analyte if evaporated to dryness. I intend to analyse the sample directly by LC/MS. Please advice on the following:

1) Can this type of sample be analyse directly by LC/MS without removing the calcium ion?

2) Can anyone suggest the best way to remove the calcium ion before analysis.

Thanks and regards

Irene

1) Yes.

Here's a simple experiment to try, assuming your compound is amenable to reverse phase LC. Filter your sample and inject it onto a reverse phase column, and do a gradient with the eluent going to your MS. If you have a switching valve, divert the void volume to waste, so all the calcium and other polar trash doesn't get into your source. If the calcium is not covalently bound to your analyte, it will elute in the void, with your analyte retained and separated from it.

Another simple solution is to use mixed-mode columns, which strongly interact with Ca++ ion. For example, our mixed-mode Primesep 200 column permanently retains Ca ion in systems with MeCN/water/organic acid. If you inject 10 uL neat probe with Ca concentration 500 ppm in this column it will take you over 1000 injections to get column saturated less than 40% with Ca ions. This column is reverse phase column and all your hydrophobic analytes can be analyzed by regular way with water/MeCN isocratic or gradient. You don’t need to worry about Ca reaching the MS.

Sample preparation with a strong cation exchanger will remove the Ca++.

Thanks you all for the fast respond

MG
I forgot to mention that l am using a HILIC column. Can your above suggestion work


Zelechonok

Will primesep100 works?

Uwe Neue
Can you suggest any catio ion exchange cartridges?

Regards
Irene

Metrohm is selling the 833 IC Liquid Handling Unit: Suppressor.
This unit is ideal to remove the cations prior to the introduction to the MS. It comes with a 10 year warranty.

For more details see: http://www.metrohm.com/products/07/833/suppressor/833sup.html

I am interested in 833 IC suppressor unit. How much it cost? We Have some money to spend this year (4-6K dollars)but we have to act fast.

Irene, I'm pretty new at HILIC and can't say with confidence how a calcium salt would behave in that mode. I assume the calcium would be very strongly retained.

Irene:

Oasis MCX cartridges - C stands for cation exchanger...

MG,
I will try anyway. Will get back to you.

Uwe Neue,
Thanks

Regards
Irene

Ta Anonymous, Dec. 11 04:46

If the amont of money will be sufficiant. Please contact your Metrohm-Representative. You may find it under:

http://www.metrohm.com/agencies.html

To Irene
Primesep 100 will work too, but it is not retain Ca permanently. Ca++ retention strongly depends on organic concentration in the mobile phase with this column. At some conditions you can have Ca eluted after spending 2 hr on a column. It all depends on what you are trying to analyze beside Ca.

Zelechonok

I am trying to analyse very polar basic compound in ground water which contain high concentration of calcium. Can the calcium ion damage the Primesep 100 column? Can the calcium ion be retain and anlyse by MS? What is the LC condition for Primesep100 for my sample.

Regards
Irene

To Irene
Ca++ is strongly retains on Primesep 100 but not damaging the column. Inorganic and organic basic compounds are retained by ion-exchange and/or hydrophobic mechanisms. Most likely you can find conditions to resolve and elute your polar basic compounds and calcium ion by varying concentration of organic component and/or concentration of acid in the mobile phase. The easiest way to do method development is to use 50 mm column. Very often you can find conditions where all peaks resolved on the short column. If you find that some peaks are closely eluted you can transfer the conditions to a longer column to achieve better separation. To detect Ca++ ion you should know what is a lowest mass you spectrometer can detect. It is not typical to look for low molecular weight ions which should be 40/2 = 20 mass, but could be done I think.
You have two choices of columns - either use Primesep 100 and develop method to separate Ca from the analytes or use Primesep 200 and trap Ca ion permanently while resolving and eluting organic components of your mixture. Primesep 200 column will allow you to do over 1000 injections before saturating with calcium ions. As a starting point you can choose MeCN/H2O/TFA-50/50/0.1 to see order of elution and retention time for different compounds in your mixture. If retention is too low increase amount of water and/or decries amount of TFA. E-mail me if you have problem with method development.

To Zelechonok

My problem is I don't know which column to purchase. I am not interested in the Ca++ in my sample. I do not want it to interfere with the analysis of polar basic compound. Do you think Primpsep100 is better for my work? Will the primpsep 100 trap the Ca too long and saturate the column. What is the tell sign that the column is saturated with calcium? Does it means that I have to purchase another new column if the column is saturated with calcium? Can the saturated column be regenerated again? If can be regenerated, what is your suggestion? Have you done a study on the loading capacity of Ca++ before saturation? Please recommend which column I should purchase because I don't intend to purchase both your suggestion.


Regards
Irene

To Irene.
Can we discuss all issues over the phone,
847 229-2629 from 9 am to 5 pm US Central Time, or direct e-mail: mail@allsep.com,
or mail me your phone number and I will call you at your convenience.

Irene,

I do believe that a sample preparation procedure will make the problem go away, i.e. remove the Ca ions. Of course, this is possibly an additional step in your work-up procedure, but it may not need to be. What kind of sample cleanup or sample concentration step are you doing currently?