Peak area variation

[Hooman]

I'm currently using an Agilent 1100 HPLC eqiupped with a binary pump, autosampler, and DAD. In order to assess reproducibility of reults, I injected successively content of a vial for 6 times, and it resulted to a mean peak area of 508.52 mAu, range from 489.3 to 528.4, standard deviation 14.86, and CV% of 2.92. I also see an increasing trend in this data set.
I wonder if this variation should be a concern, or I can simply ignore it.
Thank you.

[prepcolumn]

I'm currently using an Agilent 1100 HPLC eqiupped with a binary pump, autosampler, and DAD. In order to assess reproducibility of reults, I injected successively content of a vial for 6 times, and it resulted to a mean peak area of 508.52 mAu, range from 489.3 to 528.4, standard deviation 14.86, and CV% of 2.92. I also see an increasing trend in this data set.
I wonder if this variation should be a concern, or I can simply ignore it.
Thank you.

If it is for quantification purposes (and if you don't have a special method or SOP), this is a problem and you cannot ignore it..

[JMcK]

Generally you look for no more than 2.0% CV. If your solvent is volatile, and it's warm in your lab, you may be seeing concentration of the analyte during the analysis due to loss of solvent. One check would be to prepare 6 separate vials from the single sample prep. In this way the septa will remain intact for each injection, and that will rule out volatilization of the solvent.

[Consumer Products Guy]

I'm currently using an Agilent 1100 HPLC eqiupped with a binary pump, autosampler, and DAD.

I wonder if this variation should be a concern, or I can simply ignore it.
Thank you.

I have exact system. Our repeat injections meet system suitability requirements of < 2%RSD essentially 100% of the time, even with gradient elution. So something is wrong. I agree to start with the separate vials.