Matrix selection for polymer guanidine analysis by MALDI–TOF MS

• Matrix selection for polymer guanidine biocides characterization by MALDI–TOF MS was reported.
• Different matrices were suitable for single polymer guanidines and oxygen-containing polymer guanidines.
• Structural information of three polymer guanidine was analyzed from their best spectra.
• Quantum chemical calculations were carried out to deduce the importance of PA in matrix selection.

Due to the diversity of polymer materials, there is no universal approach in matrix-assisted laser desorption/ionization mass spectrometry (MALDI MS) to characterize a particular polymeric system. Three commercially available polymer guanidine biocides, Poly(hexamethylene guanidine) chloride (PHMG), Polyhexamethylene biguanide (PHMB), Poly-[2-(2-ethoxy)-ethoxyethyl]-guanidinium-chloride] (PEEG) were chosen for the investigation of matrix selection using MALDI–TOF MS. No unique matrix was found to satisfy all three guanidines because of the extra C-O bonds in PEEG. Sinapic acid (SA), α-Cyano-4-hydroxycinnamic acid (CHCA) seemed to be ideal for PHMG and PHMB, but 2-(4-Hydroxybenzeneazo)benzoic acid (HABA), 2,5-dihydroxybenzoic acid (DHB) were for PEEG. Proton affinities (PA) of the matrix and analyte were combined to explain this phenomenon. Matrices with lower PA were more sensitive for the polymer guanidine with lower PA.

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