Hello Randa

I'm not sure I understand your question fully.

Can you post an annotated chart/graph showing me your dilemma?

Randa,

I think you have probably answered your question yourself - i.e., your distribution may have a tail on the smaller side of the peak. Is there a reason to expect the opposite?

I've had a look at examples of PLGA distributions and there are all kinds. I expect the synthesis route and the skill account for this.

I look forward to your answer to Alan.

John.

Hi @ Randa Zoqlam

This situation where the z-average is smaller than the lowest size intensity peak is most likely due to either an initial "stretched exponential like" decay or a very fast "solvent" peak that is not making it into the distribution. Z-average and peaks are two entirely different fitting algorithms.

You may find this blog of interest: http://www.materials-talks.com/blog/2014/07/10/faq-peak-size-or-z-average-size-which-one-to-pick-in-dls/ and it might also be useful to check https://www.materials-talks.com/blog/2016/06/15/solvent-peaks-how-to-get-rid-of-the-buffersaltadditive-dls-contribution/