I need to analyse some samples for Hg content. I have some standards ranging from 0.01 to 10 ppb. However my blank shows higher intensity than my standards rang at 0.01 to 1 ppb. I use HNO3 5% in all standards.
This is one of the real problems for detection of Hg in very low levels. You have to be scrupulously clean in the make up and characterization. Hg can come in from anywhere at these low levels (and remember you're in ppb when the natural background level in tuna is 1 - 2 ppm - over a thousand tomes greater). You have probably contaminated your blank in some way with extra Hg. You'll know of course that you get mercury from H G Wells....
You have to use 'ultra-trace acid' in all your extractions/dilutions. Everything (almost) absorbs at 254 nm!
your blank might have been contaminated. You should also clean your sample introduction system with a wash solution which contains 1-3% HCl+ 2% Nitric. mercury has strong memory effect and you need to take care of that.
Another important issue is the reagents you use should be of trace analysis grade
Guys, Thanks for the tips on ultra trace analyses grade. I just ordered some. Now crossing my fingers that it will work!
Attached please find the rinsing protocol for "sticky" elements elaborated by Agilent. I have checked it and it works pretty good and is much cheaper than adding gold to rinsing solution. Also, mercury in low concentrations is very unstable. They should be kept in borosilicate glass rather than LDPE containers. Please refer to https://www.inorganicventures.com/element/mercury for more information on mercury. Also have a look on other Inorganic Ventures pages for more information about stability of other elements https://www.inorganicventures.com/stability-elements-ppb-concentration-levels
Dear Nasim, measurement of Hg on ICP-MS is tricky one. I agree with answers above ultraclean chemicals are must and try avoid using PE vessels, prefer glass and teflon if possible. You can try adding AuCl3 to your solution as this is known to decrease the memory effects - which are one of the major problems in this discipline.
I know you probably do not want to hear this but using either CV-AAS or CV-AFS methods would be much easier and more reliable.
Dear Rafal and Tomas,
I appreciate your tips and information. I actually got satisfying results with ICP-MS after using ultra pure Nitrci acid and dicromate as oxidizer. I had read in the literature that AgCl3 is the way to go, but since we had dicromate in our lab, I just used that. Use of dicromate through fully helped with Hg volatalization and mercury effects.
Thank you all for your responses and support!
There was a typo in my previous message it should read AuCl3 not AlCl3 of course!
Sorry for that.
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