How to get the absorbance 0.9 when measuring a solution of Cu 5mg/L with a flame AAS system.


We recently set up an atomic absorption spectrophotometry with a flame system. We need to test the performance of this new system by measuring the absorbance of a copper solution 5 mg/L.

However, we only obtained the maximum absorbance is 0.6. On the other hand, we found on the website of Agilent, the absorbance of Cu solution 5 mg/L is typically greater than 0.9 Abs running with a Mark 7 Atomization system.

Has anyone obtained the absorbance that is greater than 0.9 when measuring a solution of 5 mg/L Cu, and could you please share with us optimal conditions to get such a high absorbance.

Thank you very much in advance.

  • Just a thought, have you tried turning the burner for maximum path length?

  • Hi Jsh,

    We always optimize the lamp, the optical path as well as the burner position before measure the solution of 5mg/L Cu.

    And yes, we always turn the burner for the maximum path length.

    However, we never get the absorbance is 0.9 Abs.

    Have you done successfully to get such a high value?

  • Hello, with the  AA instruments. It can: achieve high sensitivity—typically 0.9 Abs. from 5 mg/L Cu; achieving these values needs to be considered; you need to consider the quality of acetylene, air free from moisture and water contents, additional optimisation of sample uptake volume, and posting of the impact bead; BTW, did you remove the mixing paddle from the spray chamber?

  • Hi DDU,

    We brought acetylene from a trustable provider.
    We also adjusted the sample uptake volume by turning the nebulizer.
    Today, we tried to the Cu solution of 5 mg/L both when having the mixing paddle and removing the mixing paddle.
    The maximum absorbance was only 0.6 with the mixing paddle. When removing the mixing paddle, the absorbance could only be more than 0.9 if we changed a sample capillary with a larger diameter.
    When we used a standard sample capillary provided by the manufacturer, the absorbance was only 0.6.
    Because there is a sentence on the website of Agilent indicating that “the absorbance of Cu solution of 5 mg/L is typically greater than 0.9 Abs running with a Mark 7 Atomization system”.
    So, could I ask that can this value be obtained in normal or specific conditions?
    Because this value is reported on the website, I think it would be better to include conditions at which the value has been obtained.

  • Hello,  Yes, as correctly mentioned, a wide bore capillary is used when higher sensitivity is required, Removing the mixing paddle will introduce more samples in flame, and the use of the mixing paddle to further deliver a very smooth mist of the sample allows bigger droplets to settle down `before moving to be burned in flame, thus sensitivity will be lesser but precision will be greater. Considering the PM Checklist  Abs value, it must be greater than > 0.5 Abs.

    The qualification Limit is  5 ppm >0.550 Abs

    I hope this clarifies the difference between using a Mixing paddle and its relation to sensitivity.

  • Hello DDU,

    Thank you very much for sharing us very useful information.

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