Chromatography Forum

Hi
I’m analyzing PAH’s by HPLC-FLD (fluorescence) in water.

I have a problem with benzo(g,h,i)perylene and indene(1,2,3-cd)pyrene. They elute very close, at 25,8 min and 26,96 min, and their wavelenghts of excitation and emission are different. I have a wavelenght program that it changes the wavelenghts between the two peaks. When the retention times changes a little the wavelength changes in the middle of a peak, and this is a problem.

I can’t resolve better the two peaks ( I worked a lot to resolve them).

Now I’m injecting twice every sample.

The wavelengths are:

Benzo(g,h,i)perylene

Ret. Time (min).- 25.8
Excitation.- 290nm
Emission.- 430nm

Indene(1,2,3-cd)pyrene
Ret. Time (min).- 26.9
Excitation.- 250nm
Emission.- 495nm

Sombody knows other wavelengths that I can use? and if it’s possible the same wavelengths for the two compounds?

Thanks

Run an excitation and emission spectrum. From that you can see whether single wavelengths for both compounds is useful.

As far as I remember, I used 300/500 nm for indeno 1,2,3
My advice: change to a column that gives better resolution for the two. Any column manufacturer claims to have one dedicated for PAH, but there are differences. Some of them will give you a test column for evaluation.