By Fabiano on Friday, January 2, 2004 - 07:57 am:
Hi,
Someone already replace flame atomic absorption by ion chromatography(non-suppresed conductivity)?
I already worked with ion chromatography and now atomic absorption looks to much unrealiable for me. the very short linear range (most time are no linear), high detection limits,etc..
Some people told me that is not possible elute heavy metals like Cd, Hg and Pb, someone have experience with this cations?
Thanks
By Chris Pohl on Monday, January 5, 2004 - 08:47 am:
Fabiano,
Actually, quite a bit of work done with cadmium and lead is in the literature (if you go to the Dionex web site at the following link search for applications data on these metals you will find a number of applications http://www.dionex.com/app/tree.taf?asset_id=291712 ). There isn't any problem eluting heavy metals of the sort from cation-exchange resins. The main issue is making sure you have a suitable detection reagent for a given transition metal. Mercury can also be eluted under similar conditions but is difficult to detect using standard colorimetric reagents.
By Fabiano on Wednesday, January 7, 2004 - 03:22 am:
Thank you Chris,
And about non-suppressed conductivity detection?
Is so difficult to reach Limit of detection of 10ppm without suppression?
By Chris Pohl on Wednesday, January 7, 2004 - 08:12 am:
Fabiano,
There is generally not a problem detecting transition metals at the low part per million level via nonsuppressed conductivity detection. Of course, relatively few real world samples contain transition metals at concentrations high enough to permit use of conductivity detection unless sample concentration techniques are employed. About the only sample type suitable for this sort of application is the analysis of metals in plating baths. Otherwise, colorimetric reagents are usually employed since detection sensitivity is typically 100-1000 times greater using this detection method. A suppressor is generally not used with this sort of application as the suppressor converts cations to the hydroxide form and with the exception of a few cations (such as manganese and zinc) the hydroxide form isn't sufficiently soluble to provide for detection of transition metal cations via conductivity detection. But, as mentioned above, use of conductivity detection even in the nonsuppressed mode isn't all that useful and most ion chromatography of transition metals is done using post-column addition of metal chelating colorimetric reagents as is detailed in the applications noted above.