Nonaqueous Capillary Electrophoresis−Mass Spectrometry of Synthetic Polymers

• Published in: Analytical chemistry (Washington) 2004-01, Vol.76 (2), p.335-344
• Main Authors: Simó, Carolina, Cottet, Hervé, Vayaboury, Willy, Giani, Olivia, Pelzing, Matthias, Cifuentes, Alejandro
• Format: Article
• Language: English
• Subjects: Analytical chemistry; Aqueous chemistry; Blood vessels; Chemistry; Chromatographic methods and physical methods associated with chromatography; Exact sciences and technology; Other chromatographic methods; Polymers; Spectrometric and optical methods; Spectrum analysis; Synthetic products
• ISSN: 0003-2700; 1520-6882
• DOI: 10.1021/ac034995q

In this work, the separation and characterization of ionizable organic polymers nonsoluble in water is carried out using nonaqueous capillary electrophoresis−ion trap mass spectrometry (NACE−MS). The polymers studied are poly(N ε-trifluoroacetyl-l-lysine) (poly(TFA-Lys)) obtained by ring-opening polymerization of the corresponding N-carboxyanhydride. Different parameters (i.e., liquid sheath nature and flow rate, electrospray temperature, and separation buffer composition) are optimized in order to obtain both an adequate CE separation and a high MS signal of the samples under study. The optimum NACE−MS separation conditions allow the molecular mass characterization of poly(TFA-Lys) up to a degree of polymerization of 38. NACE−MS provides interesting information on the chemical structure of (i) the polymer end groups and (ii) other final byproducts. The MS spectra obtained by using this CE−MS protocol confirm that the polymerization was initiated by the reaction of n-hexylamine (initiator) on the monomer. CE−MS−MS and CE−MS−MS−MS results demonstrate that two different termination reactions occurred during the polymerization process leading to the transformation of the reactive amine end group into a carboxylic or a formyl groups. Byproducts such as 3-hydantoinacetic acid or diketopiperazine were also detected. To our knowledge, this is the first work in which the great possibilities of NACE−MS and NACE−MS n for characterizing synthetic polymers are demonstrated.