DETERMINATION OF MOLECULAR-WEIGHT DISTRIBUTIONS OF POLYMERS BY MALDI-FTMS

The advantages of matrix-assisted laser desorption/ionization (MALDI) and Fourier transform mass spectrometry (FTMS) are combined to create a powerful tool for the characterization of polymer samples. MALDI per mits generation of intact, singly charged, high-mass (m/z 10(3)-10(4)) ions of polar and nonpolar analytes, while FTMS provides unique high resolution and mass accuracy. Use of a gated deceleration potential al lows for FTMS detection of MALDI-generated ions. However, when a singl e delay time is used between desorption/ionization and restoration of normal trapping potentials, mass discrimination is apparent for broad polymer distributions, Here, an integral method for obtaining molecula r weight distributions of polymers by MALDI-FTMS is presented. By mean s of a simple procedure of averaging time domain transients obtained f rom a series of polymer sample spectra recorded at systematically vari ed gated deceleration times, accurate polymer distributions are obtain ed. The technique is demonstrated with several poly(ethylene glycol) s amples containing oligomers with masses covering a 10 kDa mass range.