ICPMS analysis of Au ang Ag

[joelyue]

Hi,
i am using the Agilent ICPMS7500s to quantify trace amount of Gold and Silver. However i find that these 2 ions have carry over and memory effect. Can anyone advise what is causing this and how to solve this issue?
FYI i have tried flushing my system with dilute HNO3 but the issue still persists.

[jerole]

The problem with Au is that it deposits on the cones, therefore rinsing won't help much and you have to clean the cones frequently.
What is the concentration range you are working with? Maybe you have to dilute the sample more.

[yangz00g]

HNO3 only is not enough, add, say 10%, HCl.

[Biocheckup]

You may also consider using mercury to amalgamate gold (we do it the reverse way, using gold to amalgamate mercury and control memory effects).

[joelyue]

i am working with 1% HNO3 and i am working with standards of highest concentration of 1ppb.
i have tried using HCl but it causes alot of interferences later when i try to analyse elements other than Au and Ag. The extended flushing and cleaning i have to do later is not justifiable as time is very tight in my operations.
also can explain more in how to amalgate Au using Hg?

[Biocheckup]

Gold is used to suppress Hg memory effects; typically a 100 ppm in dilute nitric acid is used for a mercury concentration in the 1-10 ppm range.

You'll find information on this in EPA 200.8 release 5.4

http://www.caslab.com/EPA-Methods/PDF/200_8.pdf

It's described as an amalgam technique (though whether it's really the mechanism has been debated). We used this gold addition with success for urine Hg determination. Curiously we did not need it for whole blood Hg. Some other matrix component may be playing a role there.