The subject of Hg washout was discussed on this very ListServer just last month.
A lot of good information was posted, of which the key suggestions seem to be:
Keep your top calibration standard as low as possible. The measurement of Hg in
drinking water under UK standard protocols requires a DL of 0.1ppb and we would
standardise up to a top calibration standard of around 2ppb. There are few
carry-over problems at these levels.
To stabilise the Hg, add 200ppb Au to every solution as soon as they are
received (or prepared). We also add 1% HNO3 and 0.5% HCl. Add the Au directly
to each sample, rather than using the on-line system. The on-line addition of
Au does not stop loss of the Hg in the sample container and sample uptake
Be very careful of the material you use for the preparation and storage of your
samaples and standards. Hg adsorbs very quickly onto many plastic materials,
although the stabilisation with Au improves things greatly.
If you add 200ppb Au to your rinse solution (in a matrix of 2% HNO3 and 1% HCl),
the washout even from high levels is quite acceptable. However, after repeated
analysis of high (ppm) levels of Hg, the background level for Hg does increase
slightly and can only be reduced by thorough cleaning of the glassware and
If you need to measure Hg at significantly below 0.1ppb, then the more you can
do to limit the possibility of contamination of the system at ppt levels, the
Someone mentioned to me that cyanide works rather well for cleaning up Hg
Best of luck.
UK ICP-MS Specialist
______________________________ Reply Separator _________________________________
Subject: Analysis of mercury
Author: Non-HP-jean-pierre.blouin ([log in to unmask])
Date: 11/06/98 19:26
We are now looking for the analysis of mercury at a sub-ppb level in
water by ICP-MS (HP 4500). Does someone has any experience with this
type of analysis.
Chef de Division Chimie Inorganique
Centre d'Expertise en Analyses Environnementales du Québec
Courriel: [log in to unmask]