analyte peak before void time

[aaffum1]

my analyte elutes before the void time.
Conditions:
25cm x0.46cm c-18 5um column
flow rate 1.5ml/min
uv detection
sample prepared in water
mobile phase 50:50:0.0029 (v/v/v) ACn:water: acetic acid

[nschwartz]

What is your analyte?

[tom jupille]

and what are the elution time of your analyte and the measured dead (void) time?

[ljc]

Never mind the analyte, what's your question? Anyway, I've seen where the analyte could be excluded by the column and the solvent dip or inflection may not be the true void volume of the system.

[tom jupille]

Actually, defining "void volume" is something of a can of worms. There were a number of discussions a decade or so ago that are still in the archives:
http://www.lcresources.com/discus/messa ... 20000443pm
http://www.lcresources.com/discus/messa ... 20040107am
http://www.lcresources.com/discus/messa ... 20041222pm