Bromide Ions Interfering with my Nitrate Count

[rndmnbr]

I have a dionix ICS 3000 variable wavelength detector set only to 210, which is only supposed to pick up the value of my nitrate ions. I have eliminated all other sources of error I can, but I seem to be picking up the value of the bromide ions in the solution as well which is drastically increasing my nitrite count.

I have been told I may be able to adjust the wavelength to eliminate the bromide interference, but I don't know if that is accurate, or which direction to adjust the wavelength to optimize the interference reduction.

Does anyone have any experience with this or any advice?

[Jumpshooter]

Bromine absorbs ~ 163.3 nm; at what nm sector do you see the nitrate peak (should be different from 163.3)? If your peak for nitrate is below this value, then set the detector so that the 163.3 nm range is excluded; that ought to eliminate the interference.

[Bruce Hamilton]

I doubt excluding wavelength below 180nm is feasible on most instruments, given that atmospheric gases absorb below about 190 nm.

Check the Dionex web site, as they may have relevant application notes.

Surely the system is resolving the nitrate and bromide, so there should be no interference, if it isn't, then fix the chromatography. From memory, 205-210nm can be used for bromide and nitrate, provided they are resolved.

The following may help with the UV issues..

"Simultaneous determination of bromide and nitrate in contaminated waters by ion chromatography using amperometry and absorbance detectors"
K. Tirumalesh
Talanta
Volume 74, Issue 5, 15 February 2008, Pages 1428-1434

[Consumer Products Guy]

Couldn't you use silver extraction cartridge (Maxi Clean Ag from Grace Davison/Alltech) to pull out the bromide before analysis?

[Markus Laeubli, Metrohm]

Dear rndmnbr

We did some applications for the analysis of nitrite and nitrate applying UV detection. We ususally use 220 nm. Using these conditions we do not recognise any signal for bromide. I therefore assume that you have an other interference.