ICP-OES 725 ES

Hey there, i´m working with the ICP-OES 725-ES and i have to detect Ca,Mg,K in a 5% Nacl matrix. The icp won´t detect kalium correctly so i have to dilute the samples 1:2 (50%). But if i do it i don`t reache the limit of determination. I show the method in the picture below maybe anyone can tell me

  • Hello,

    it's not clear what's not correctly but what could be interfering on the results is the EIE (Easy Ionized Element) effect. This effect is most suffered for the Easy Ionised ones, like Na and K. This effect results into a bad calibration curve. As a solution for the problem you can dilute the samples or a ionization buffer like 2% CsCl could be added. 

    To give a better answer to you questions I want to know what's wrong if you measure in the undiluted samples and what is the detection limit in the solution for the K. 

    Cheers,

    Edgar

  • Good morning,

    the pictures show that the argon factor blow up and the qc`s don`t match anymore. At the other elements like magnesium you can see that the calibration works. If i measure in the regular 1% HNO³  the detection limits reached under 0,25 ppm but in the NaCl matrix with 5% NaCl it works bad.

  • Are you using an internal standard? Why is your plasma gas 16.5L/min?  that seems a bit high

  • hey,

    no i don`t use an internal. I just take over the method from the last one who works here and now i begin to optimize the analysis.

  • 5% NaCl solvent is hard matrix for ICP-OES. It could be made EIE and contamination.

    First step, We need to check dark current, wavelength calibration, torch alignment. it must be normal result.

    I recommend ASA( Argon saturation Accessory) and adjust torch height for good optimization position in condition tab.

    If from 0.1 to 1.0 ppm range is bad, it was no reason for detection limit about 0.25 ppm.

  • Good morning,

    if i measure in the 1%HNO³  the calibration works fine. I know that the NaCl-matrix is bad for the icp and i tell it so often to the chemist. In the upper Picture you can see a regular calibration that we use for water solutions.

    The torch alignment is good an the wave lenght calibration is from 167.019nm to 766.491nm. The dark current only show that is all fine but no value.

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