[javert]

Hi everyone.

In our laboratory we measure mercury in water at the μg/L level. So far we have been preparing the calibration standards and QC solutions by consecutive dilutions of a commercial 1 000 mg / L standard solution. The issue is that an overall dilution factor of 10E6 means a lot of dilutions (or few but very big dilutions), and I suspect that is the underlying cause for the discrepancies between calibration standards and QC solutions.

I have been searching for commercial low level mercury standards but the lowest level I can find is 10 mg / L. Knowing that mercury is usually evaluated at μg / L levels or even ng / L levels, it seems odd to me that no one offers standards closer to this levels. Is there a reason for this? Do you know a supplier who offers a commercial solutions at about 100 μg / L?

I'm aware of all the cautions needed to avoid contamination from other sources but, assuming correct clean room practices, is the mercury concentration still unstable at μg/L levels due to intrinsic factors?

[Borek]

From what I remember low concentration solutions tend to lose some of the substances dissolved due to their adsorption on the internal surfaces. That's not a problem for higher concentrations, but when you get down to ppm levels and below, it can't be ignored.

But I have not dealt with these things for almost 30 years so I can be completely wrong.