the detection limit is 0.6ppb for Zinc when we rinsed our Digi Tube with HNO3, what should I do to reduce the detection limit?


we still got very high Detection limit of 0.6 ppb for Zinc after we rinsed the Digi Tube with 2% HNO3. Does anybody know how to reduce the detection limit? 

we use 2% HNO3 to rinse the Digi Tube, then fill the tube with 2% HNO3, and let them stand overnight with a lid covering. next day , we created the following calibration curve, but still have high background which lead to 0.6ppb. 

we assume there are possibly two reasons to introduce this high background: 

1. water quality. we use water for injection from Baxter. please see the below picture. we want to know what the background reading if milli Q water is used. 

2. another is the instrument setting. we set the instrument setting: 

Thank you 

Best regards, 

Di Xu

  • I never use sterile water for ICP-MS since it's not good for trace metal work (that wasn't its designed purpose). Sterile water is typically just distilled water. You will want DI, Milli-Q (18.2 megaohm) or comparable.

    In a lab with good reagents (water and optima grade acids), good lab practice (prewashing), on a clean instrument (clean sample intro) my zinc counts are <1000. This is not always achievable in labs if proper care is not taken during sample prep or if the lab environment is not clean enough. 

  • Hi Cheltajc, 

    Thank you for your suggestions. 

    yes, I agreed with you . yesterday we tried different water and found out that the water we are currently using has around 11 ppb zinc. 

    after we changed the water, we obtain the following results: 

    now the root cause was found. 

    Thank  you

    Best regards, 

    Di Xu

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