Chromatography Forum

Hi,

I'm currently developing methods to analyze molecules without useful chromophores for UV detection, i.e. fatty alcohols from C12 on and their mono- and diesters with various dicarboxylic acids. I'm using a PL-ELS 2100 ICE and trying to get a setting which detects also the low MW compounds (C12-OH) without success. I've tried different settings for gas flow, nebulizer and evap temp, C18-OH are detected well, but the smaller ones don't give a signal, no matter which setting I chose. Is there a general limit on the lower side? Eluent is water/ACN, flow is 0,5 ml/min on a standard C18ec column. I tried temps down to 15 °C.
Anyone out there who tried this with success?

I have never used ELSD, but from theory it is known that whatever is volatile cannot be seen in ELSD: C12 alcohols have a significant vapour pressure, hence you will have troubles seeing them in ELSD

Have a GC handy?

The sample contains (nearly) non-volatile compounds, so GC is not an option.
I tried some more settings and contacted ex PL ex Varian (now Agilent, not easy to get a competent person), they have a table with basic
settings for various analytes. I now see even C12. Reducing the nebulizer flow helped a lot.

Could you please please send me this list at joerg_dot_johannes_at_laus_dot_de? I have a new (used) ELSD and I'd be happy to avoid as many mistakes as possible.
Thanks a lot!
Jörg

I have never used ELSD, but from theory it is known that whatever is volatile cannot be seen in ELSD: C12 alcohols have a significant vapour pressure, hence you will have troubles seeing them in ELSD

See above.

Could you please please send me this list at joerg_dot_johannes_at_laus_dot_de? I have a new (used) ELSD and I'd be happy to avoid as many mistakes as possible.
Thanks a lot!
Jörg

...sent.

Could you please forward me that list as well? - sounds very informative. Thank you!

c_n_arden at yahoo.com