Acetate ion determination polymers using KOH

[outfield3678]

I am using As19 thermo column and DRS600 suppressor on ICS6000. The Eluent is KOH.   The suppressor is operated in Dynamic mode.  Acetate seems to appear and then disappear.  I am trying to calibrate 0.25 mg/L  to 20 mg/L.  along with Fluoride, nitrate, chloride, sulfate, phosphate.   I can get good linearity with the other analytes but the acetate ion is a problem.  I use 10mM to 45mM ramp.  What should be detection be for acetate?    Is the problem linked to the suppressor .  Should I just analyze without the suppression or lower the current thus maintain a higher pH..  Please help!!!   

[Molly_I2]

Hello @outfield3678 and thank you for posting a question in the forum. We will gather what we can and sync you up with the team to support your inquiry. We will message on this thread if any additional information is needed to support you. @The_Ion_Lady and @chris-shevlin - please help me welcome @outfield3678.

[Molly_I2]

@outfield3678 I spoke with our applications team and they provided some input for you here.

They recommended you reach out to technical support (link here:Contact Us | Thermo Fisher Scientific - US) so they can review your data with respect to the presence of acetate in your samples. They added that because acetate is the anion of an organic acid (acetic acid), its calibration will not be as linear as the inorganic anions for your chosen calibration range. That is because it will be less dissociated at high concentrations. Therefore, for the chosen range a polynomial fit (available in Chromeleon) will be better. Whatever the issue you have with acetate is, it is unlikely to be related to the suppressor or your separation conditions. With a review of your data the customer support team should be able to assist you. 

Let us know if you feel this helps give you the direction you need, or if i can loop anyone else into the conversation.

[The_Ion_Lady]

Hello @outfield3678,

For most organic ions, the calibration tends to be curved rather than linear due to the weak organic acid bonds, especially in such large range calibration of 100 fold. Obviously, if you look at a smaller range the calibration will look linear but when extended it will be curved.

I would calibrate inorganics as linear and organic species as polynomial fit which can be selected for individual analytes if you want to calibrate with that range.