PAH Standard preparation

[Peppels]

Good afternoon,
After lots of attempts, seems that the extraction process using the MW works great.
The issue I'm facing right now, is related to the calibration verification standard. The standard solutions I'm using are stored at -18°C and I usually remove them from the freezer in the early morning.
How much time do I have to wait to have a complete solubilization of the analytes, because preparing the ICV just after two hours, generally leads to an underestimated result (up to 20% less than expected).
Thank you.

[cjm]

I would ensure the cold solution is not only heated but sonicated for several minutes to break up any small crystals that may be present. Doing this every time helped us with stability issues with the heavier PAHs.

Also be aware an ICV testing out 20% from expected values doesn't automatically mean the ICV is bad. The calibration could be biased 20% and the ICV could be ok. I would suggest a third standard to check both your primary and secondary sources.