Hi,
Iam screening carbamate pesticides on an API2000 with an 1100 Agilent LC. My column is a phenomenex Luna 3u C18(2) 150 x 2.0mm. My mobile phase is A=Water w/ 10mm Ammonium Acetate and .1% Formic Acid. B=Acetonitrile with 10mm Ammonium Acetate and .1% Formic Acid. My current gradient is A/B (95:5) to A/B (5:95) over 20 min, to A/B (95:5) in 2 min, then a hold at A/B (95:5) for 5 min. I am injecting a 10 ul sample injection which is in 80:20 MeOH/Water. I am unable to reproduce retention times and area counts. Any thoughts or suggestions? Also I am finding that with this gradient my pesticides are not eluting until 10 mins and later. Whereas phenomenex's elutes at 5 mins under the same conditions just a little bit different gradient. Instead theirs is A/B (90:10) to A/B (30:70) in 20 mins to A/B (90:10) in 2 mins then hold 5 mins at A/B (90:10). Any thoughts or suggestions on how to reproduce the same chromatogram as phenomenex's or close to it without turning some peaks into short, broad, jagged peaks? Thanks

On the retention time issue, your re-equilibration time at the end seems a little short for that length of column, assuming you are running in the 0.2 - 0.3 mL/min flow rate range. Try 10 min.

If there are problems specifically with your early eluting peaks, especially if they look ugly (fronting, split), try a weaker injection solvent. If the injection solvent can't be changed, try a smaller injection volume.

Is Phenomenex using the same buffers as you? Same flow rate? If so, try starting with their gradient and change from there to get what you need.