Most synthetic polymers ionize via alkali metal ion attachment in the gas phase.
The intense peaks in the PMMA spectrum are the result of sodium cationization. This property must be taken into account when choosing solution and matrix conditions in order to successfully obtain mass spectra of polymers. The matrix is titrated with a solution of potassium hydroxide and aliquots of the resulting titration are taken at the given pH values. The analyte sample contains a mixture of PMMA and the protein alpha -cobratoxin from the venom of the cobra N. n. siamensis . The matrix functions best at its intrinsic pH, as shown in the top spectrum.