You need an appropriate matrix compound, which is able to crystalize together with your polymer. It depends on the type of polymer, see literature. (it is important to have a solvent in which both are soluble)

The MALDI spectrum will show the size distribution of the polymer. Each peak indicates an polymer of given length. The m/z difference is the mass of the repeating unit.

The more accurate answer would require more information.

Gy. Gyémánt

Dear Dr. Gyöngyi Gyémánt,

Many thanks for your reply.

In detail,

I have group 4 complexes with one ligand one metal and two iso-propoxide units. When I used these complexes for ROP (ring-opening polymerization) of rac-lactide, with some complexes Mn I achieved near like theoretical Mn and some other complexes I achieved more than theoretical Mn. Some of the cases I got less than theoretical Mn also.

So, how can I conform whether two iso-propoxide units initiated the polymerization or one iso-propoxide unit involved.

Two iso-propoxide if initiate then two polymer chains will produce from metal centre or If one iso-propoxide initiate then one polymer chain will produce from metal centre. From MALDI-TOF how to determine regarding how many active sites? 

MALDI-TOF experiments we use to carried out using a dihydroxy benzoic acid (DHB) matrix in THF at a loading of 1:5 (polymer : matrix) with KOAc as the cationizing agent.

Thank you,

Sreenath.