Structural analysis of anionic surfactants in MALDI negative ion mode using "SpiralTOF™-plus"
MSTips No. 333
The matrix-assisted laser desorption ionization time-of-flight mass spectrometer (MALDI-TOFMS) is a powerful tool in analyzing polymers. Since MALDI mainly produces singly charged ions, m/z values in the mass spectrum are the same as polymer ions' mass. Using the high mass resolution MALDI-TOFMS, it is possible to identify the compositions of polymer series by their repeating unit and the end-group, and calculate the molecular weight distributions of each. The Kendrick Mass Defect (KMD) was recently applied to the polymer analysis to visualize polymer series contained in complex high-mass resolution mass spectra. In addition, the TOF-TOF option enables structural analysis, especially for end-group analysis, of polymers from fragment ions generated by high-energy collision-induced dissociation (HE-CID). In polymer analysis with MALDI-TOFMS, sample, matrix and cationizing agent solution are mixed, dropped onto a target plate, air-dried, and measured. In general, the target polymer ions will be observed in the positive ion mode as [M+Li]+, [M+Na]+ or [M+K]+ according to the cationizing agents. However, polymers that have sulfate or phosphate end-groups can be detected in the negative ions. In this report, we will show the analysis of the mixture of anionic and nonionic surfactants.