Chromatography Forum

Hi!!

Anybody know the name of the chromatographic technique in which the mobile phase is added an additive (which absorbs the UV and which is not retained), and a UV detector is used and in which the peaks are detected as negative (by displacement in the cell that produces the additive absorbing analyte)?

Some reference??

Thanks!

I've heard it called "indirect UV detection" or "vacancy chromatgraphy".

Not sure what its called, but can't you set the detector to reverse it??

I'd call it Differential UV or Negative UV.

Scott's on the ball:

Vacancy chromatography

A technique in which a mobile phase additive causes a positive detector signal output. When a solute elutes from the column, it dilutes the signal and gives a negative peak or a vacancy. The technique has been most recently applied to single column ion chromatography, in which mobile phases that absorb in the UV region, such as citrate and phthalate buffers, are used. When a nonabsorbing anion elutes, it dilutes the UV absorbing background and causes a negative peak. The detector output leads are usually reversed to make the chromatogram look normal.

tHANKS sCOTT AND CODY!!!

In-direct UV. I performed this on a product not so long ago. Not the greatest method in the world but does the trick if you don't have an IC or something similar.

Basically works on the fact the sample will 'block' out UV rather than absorb it. You will end up with Negative peaks as a response.

Thanks LC Adict!

Another question.
Somebody know what are the additives for uv indirect, aplied for reverse phase chromatography??? And concentration???