Double Peaks of the Same Analyte

[Envirosun]

I am running a 6890 Agilent GC with splitless flow. I recently dropped my run time to 14.25 minutes for pesticides and the chromatography looked great. However, suddenly, I began getting what appear to be double peaks for the same analyte: a large normal peak and a small hump attached following the initial peak. I can only assume this second small shoulder is part of the initial "parent" analyte, since it is occurring for each peak in the first half of the run. I switched back to my normal run of 24 minutes to see if there were any change--there was not. Has anyone experienced this, or are there any suggestions in correcting the problem. It is making integration and calibration impossible--I cannot rely on what may be part of the same analyte. Thanks in advance for any advice!

[Rick]

What is your old and new oven temperature pgrm?
What is your solvent and column?

[jh1]

Which pesticide and have you purchased new standards recently?

This secondary peak could simply be a different isomer of the pesticide.

[fsistere]

Hi
I'm sorry about my (very) bad english
If appears doublepic in many pics of your cromatogram it's possible a problem with the injection.

[s2008]

probably the column was dead or overloading. Check with new column and smaller injection volume.

[danicrd]

try lower initial temp of column: the problem is simply injection problem
good luck

[Suresh Seethapathy]

I have seen this with a Thermo Focus GC and AS 3000 autosampler. Simply increasing the injection needle dwell time to 2 seconds solved my problem. Never noticed anything like that with the Agilent autosampler which seems to have the fastest injection i know of.

[frage]

Hello!
test see if the gold Plated is clean?

P/N 18740-20885